1 |
/* |
2 |
* %W% %E% |
3 |
* |
4 |
* Copyright 2005 Sun Microsystems, Inc. All rights reserved. |
5 |
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
6 |
*/ |
7 |
|
8 |
package java.util; |
9 |
import java.util.*; // for javadoc |
10 |
import java.io.Serializable; |
11 |
import java.io.ObjectOutputStream; |
12 |
import java.io.IOException; |
13 |
import java.lang.reflect.Array; |
14 |
|
15 |
/** |
16 |
* This class consists exclusively of static methods that operate on or return |
17 |
* collections. It contains polymorphic algorithms that operate on |
18 |
* collections, "wrappers", which return a new collection backed by a |
19 |
* specified collection, and a few other odds and ends. |
20 |
* |
21 |
* <p>The methods of this class all throw a <tt>NullPointerException</tt> |
22 |
* if the collections or class objects provided to them are null. |
23 |
* |
24 |
* <p>The documentation for the polymorphic algorithms contained in this class |
25 |
* generally includes a brief description of the <i>implementation</i>. Such |
26 |
* descriptions should be regarded as <i>implementation notes</i>, rather than |
27 |
* parts of the <i>specification</i>. Implementors should feel free to |
28 |
* substitute other algorithms, so long as the specification itself is adhered |
29 |
* to. (For example, the algorithm used by <tt>sort</tt> does not have to be |
30 |
* a mergesort, but it does have to be <i>stable</i>.) |
31 |
* |
32 |
* <p>The "destructive" algorithms contained in this class, that is, the |
33 |
* algorithms that modify the collection on which they operate, are specified |
34 |
* to throw <tt>UnsupportedOperationException</tt> if the collection does not |
35 |
* support the appropriate mutation primitive(s), such as the <tt>set</tt> |
36 |
* method. These algorithms may, but are not required to, throw this |
37 |
* exception if an invocation would have no effect on the collection. For |
38 |
* example, invoking the <tt>sort</tt> method on an unmodifiable list that is |
39 |
* already sorted may or may not throw <tt>UnsupportedOperationException</tt>. |
40 |
* |
41 |
* <p>This class is a member of the |
42 |
* <a href="{@docRoot}/../guide/collections/index.html"> |
43 |
* Java Collections Framework</a>. |
44 |
* |
45 |
* @author Josh Bloch |
46 |
* @author Neal Gafter |
47 |
* @version %I%, %G% |
48 |
* @see Collection |
49 |
* @see Set |
50 |
* @see List |
51 |
* @see Map |
52 |
* @since 1.2 |
53 |
*/ |
54 |
|
55 |
public class Collections { |
56 |
// Suppresses default constructor, ensuring non-instantiability. |
57 |
private Collections() { |
58 |
} |
59 |
|
60 |
// Algorithms |
61 |
|
62 |
/* |
63 |
* Tuning parameters for algorithms - Many of the List algorithms have |
64 |
* two implementations, one of which is appropriate for RandomAccess |
65 |
* lists, the other for "sequential." Often, the random access variant |
66 |
* yields better performance on small sequential access lists. The |
67 |
* tuning parameters below determine the cutoff point for what constitutes |
68 |
* a "small" sequential access list for each algorithm. The values below |
69 |
* were empirically determined to work well for LinkedList. Hopefully |
70 |
* they should be reasonable for other sequential access List |
71 |
* implementations. Those doing performance work on this code would |
72 |
* do well to validate the values of these parameters from time to time. |
73 |
* (The first word of each tuning parameter name is the algorithm to which |
74 |
* it applies.) |
75 |
*/ |
76 |
private static final int BINARYSEARCH_THRESHOLD = 5000; |
77 |
private static final int REVERSE_THRESHOLD = 18; |
78 |
private static final int SHUFFLE_THRESHOLD = 5; |
79 |
private static final int FILL_THRESHOLD = 25; |
80 |
private static final int ROTATE_THRESHOLD = 100; |
81 |
private static final int COPY_THRESHOLD = 10; |
82 |
private static final int REPLACEALL_THRESHOLD = 11; |
83 |
private static final int INDEXOFSUBLIST_THRESHOLD = 35; |
84 |
|
85 |
/** |
86 |
* Sorts the specified list into ascending order, according to the |
87 |
* <i>natural ordering</i> of its elements. All elements in the list must |
88 |
* implement the <tt>Comparable</tt> interface. Furthermore, all elements |
89 |
* in the list must be <i>mutually comparable</i> (that is, |
90 |
* <tt>e1.compareTo(e2)</tt> must not throw a <tt>ClassCastException</tt> |
91 |
* for any elements <tt>e1</tt> and <tt>e2</tt> in the list).<p> |
92 |
* |
93 |
* This sort is guaranteed to be <i>stable</i>: equal elements will |
94 |
* not be reordered as a result of the sort.<p> |
95 |
* |
96 |
* The specified list must be modifiable, but need not be resizable.<p> |
97 |
* |
98 |
* The sorting algorithm is a modified mergesort (in which the merge is |
99 |
* omitted if the highest element in the low sublist is less than the |
100 |
* lowest element in the high sublist). This algorithm offers guaranteed |
101 |
* n log(n) performance. |
102 |
* |
103 |
* This implementation dumps the specified list into an array, sorts |
104 |
* the array, and iterates over the list resetting each element |
105 |
* from the corresponding position in the array. This avoids the |
106 |
* n<sup>2</sup> log(n) performance that would result from attempting |
107 |
* to sort a linked list in place. |
108 |
* |
109 |
* @param list the list to be sorted. |
110 |
* @throws ClassCastException if the list contains elements that are not |
111 |
* <i>mutually comparable</i> (for example, strings and integers). |
112 |
* @throws UnsupportedOperationException if the specified list's |
113 |
* list-iterator does not support the <tt>set</tt> operation. |
114 |
* @see Comparable |
115 |
*/ |
116 |
public static <T extends Comparable<? super T>> void sort(List<T> list) { |
117 |
Object[] a = list.toArray(); |
118 |
Arrays.sort(a); |
119 |
ListIterator<T> i = list.listIterator(); |
120 |
for (int j=0; j<a.length; j++) { |
121 |
i.next(); |
122 |
i.set((T)a[j]); |
123 |
} |
124 |
} |
125 |
|
126 |
/** |
127 |
* Sorts the specified list according to the order induced by the |
128 |
* specified comparator. All elements in the list must be <i>mutually |
129 |
* comparable</i> using the specified comparator (that is, |
130 |
* <tt>c.compare(e1, e2)</tt> must not throw a <tt>ClassCastException</tt> |
131 |
* for any elements <tt>e1</tt> and <tt>e2</tt> in the list).<p> |
132 |
* |
133 |
* This sort is guaranteed to be <i>stable</i>: equal elements will |
134 |
* not be reordered as a result of the sort.<p> |
135 |
* |
136 |
* The sorting algorithm is a modified mergesort (in which the merge is |
137 |
* omitted if the highest element in the low sublist is less than the |
138 |
* lowest element in the high sublist). This algorithm offers guaranteed |
139 |
* n log(n) performance. |
140 |
* |
141 |
* The specified list must be modifiable, but need not be resizable. |
142 |
* This implementation dumps the specified list into an array, sorts |
143 |
* the array, and iterates over the list resetting each element |
144 |
* from the corresponding position in the array. This avoids the |
145 |
* n<sup>2</sup> log(n) performance that would result from attempting |
146 |
* to sort a linked list in place. |
147 |
* |
148 |
* @param list the list to be sorted. |
149 |
* @param c the comparator to determine the order of the list. A |
150 |
* <tt>null</tt> value indicates that the elements' <i>natural |
151 |
* ordering</i> should be used. |
152 |
* @throws ClassCastException if the list contains elements that are not |
153 |
* <i>mutually comparable</i> using the specified comparator. |
154 |
* @throws UnsupportedOperationException if the specified list's |
155 |
* list-iterator does not support the <tt>set</tt> operation. |
156 |
* @see Comparator |
157 |
*/ |
158 |
public static <T> void sort(List<T> list, Comparator<? super T> c) { |
159 |
Object[] a = list.toArray(); |
160 |
Arrays.sort(a, (Comparator)c); |
161 |
ListIterator i = list.listIterator(); |
162 |
for (int j=0; j<a.length; j++) { |
163 |
i.next(); |
164 |
i.set(a[j]); |
165 |
} |
166 |
} |
167 |
|
168 |
|
169 |
/** |
170 |
* Searches the specified list for the specified object using the binary |
171 |
* search algorithm. The list must be sorted into ascending order |
172 |
* according to the <i>natural ordering</i> of its elements (as by the |
173 |
* <tt>sort(List)</tt> method, above) prior to making this call. If it is |
174 |
* not sorted, the results are undefined. If the list contains multiple |
175 |
* elements equal to the specified object, there is no guarantee which one |
176 |
* will be found.<p> |
177 |
* |
178 |
* This method runs in log(n) time for a "random access" list (which |
179 |
* provides near-constant-time positional access). If the specified list |
180 |
* does not implement the {@link RandomAccess} interface and is large, |
181 |
* this method will do an iterator-based binary search that performs |
182 |
* O(n) link traversals and O(log n) element comparisons. |
183 |
* |
184 |
* @param list the list to be searched. |
185 |
* @param key the key to be searched for. |
186 |
* @return the index of the search key, if it is contained in the list; |
187 |
* otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>. The |
188 |
* <i>insertion point</i> is defined as the point at which the |
189 |
* key would be inserted into the list: the index of the first |
190 |
* element greater than the key, or <tt>list.size()</tt>, if all |
191 |
* elements in the list are less than the specified key. Note |
192 |
* that this guarantees that the return value will be >= 0 if |
193 |
* and only if the key is found. |
194 |
* @throws ClassCastException if the list contains elements that are not |
195 |
* <i>mutually comparable</i> (for example, strings and |
196 |
* integers), or the search key in not mutually comparable |
197 |
* with the elements of the list. |
198 |
* @see Comparable |
199 |
* @see #sort(List) |
200 |
*/ |
201 |
public static <T> |
202 |
int binarySearch(List<? extends Comparable<? super T>> list, T key) { |
203 |
if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD) |
204 |
return Collections.indexedBinarySearch(list, key); |
205 |
else |
206 |
return Collections.iteratorBinarySearch(list, key); |
207 |
} |
208 |
|
209 |
private static <T> |
210 |
int indexedBinarySearch(List<? extends Comparable<? super T>> list, T key) |
211 |
{ |
212 |
int low = 0; |
213 |
int high = list.size()-1; |
214 |
|
215 |
while (low <= high) { |
216 |
int mid = (low + high) >> 1; |
217 |
Comparable<? super T> midVal = list.get(mid); |
218 |
int cmp = midVal.compareTo(key); |
219 |
|
220 |
if (cmp < 0) |
221 |
low = mid + 1; |
222 |
else if (cmp > 0) |
223 |
high = mid - 1; |
224 |
else |
225 |
return mid; // key found |
226 |
} |
227 |
return -(low + 1); // key not found |
228 |
} |
229 |
|
230 |
private static <T> |
231 |
int iteratorBinarySearch(List<? extends Comparable<? super T>> list, T key) |
232 |
{ |
233 |
int low = 0; |
234 |
int high = list.size()-1; |
235 |
ListIterator<? extends Comparable<? super T>> i = list.listIterator(); |
236 |
|
237 |
while (low <= high) { |
238 |
int mid = (low + high) >> 1; |
239 |
Comparable<? super T> midVal = get(i, mid); |
240 |
int cmp = midVal.compareTo(key); |
241 |
|
242 |
if (cmp < 0) |
243 |
low = mid + 1; |
244 |
else if (cmp > 0) |
245 |
high = mid - 1; |
246 |
else |
247 |
return mid; // key found |
248 |
} |
249 |
return -(low + 1); // key not found |
250 |
} |
251 |
|
252 |
/** |
253 |
* Gets the ith element from the given list by repositioning the specified |
254 |
* list listIterator. |
255 |
*/ |
256 |
private static <T> T get(ListIterator<? extends T> i, int index) { |
257 |
T obj = null; |
258 |
int pos = i.nextIndex(); |
259 |
if (pos <= index) { |
260 |
do { |
261 |
obj = i.next(); |
262 |
} while (pos++ < index); |
263 |
} else { |
264 |
do { |
265 |
obj = i.previous(); |
266 |
} while (--pos > index); |
267 |
} |
268 |
return obj; |
269 |
} |
270 |
|
271 |
/** |
272 |
* Searches the specified list for the specified object using the binary |
273 |
* search algorithm. The list must be sorted into ascending order |
274 |
* according to the specified comparator (as by the <tt>Sort(List, |
275 |
* Comparator)</tt> method, above), prior to making this call. If it is |
276 |
* not sorted, the results are undefined. If the list contains multiple |
277 |
* elements equal to the specified object, there is no guarantee which one |
278 |
* will be found.<p> |
279 |
* |
280 |
* This method runs in log(n) time for a "random access" list (which |
281 |
* provides near-constant-time positional access). If the specified list |
282 |
* does not implement the {@link RandomAccess} interface and is large, |
283 |
* this method will do an iterator-based binary search that performs |
284 |
* O(n) link traversals and O(log n) element comparisons. |
285 |
* |
286 |
* @param list the list to be searched. |
287 |
* @param key the key to be searched for. |
288 |
* @param c the comparator by which the list is ordered. A |
289 |
* <tt>null</tt> value indicates that the elements' <i>natural |
290 |
* ordering</i> should be used. |
291 |
* @return the index of the search key, if it is contained in the list; |
292 |
* otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>. The |
293 |
* <i>insertion point</i> is defined as the point at which the |
294 |
* key would be inserted into the list: the index of the first |
295 |
* element greater than the key, or <tt>list.size()</tt>, if all |
296 |
* elements in the list are less than the specified key. Note |
297 |
* that this guarantees that the return value will be >= 0 if |
298 |
* and only if the key is found. |
299 |
* @throws ClassCastException if the list contains elements that are not |
300 |
* <i>mutually comparable</i> using the specified comparator, |
301 |
* or the search key in not mutually comparable with the |
302 |
* elements of the list using this comparator. |
303 |
* @see Comparable |
304 |
* @see #sort(List, Comparator) |
305 |
*/ |
306 |
public static <T> int binarySearch(List<? extends T> list, T key, Comparator<? super T> c) { |
307 |
if (c==null) |
308 |
return binarySearch((List) list, key); |
309 |
|
310 |
if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD) |
311 |
return Collections.indexedBinarySearch(list, key, c); |
312 |
else |
313 |
return Collections.iteratorBinarySearch(list, key, c); |
314 |
} |
315 |
|
316 |
private static <T> int indexedBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) { |
317 |
int low = 0; |
318 |
int high = l.size()-1; |
319 |
|
320 |
while (low <= high) { |
321 |
int mid = (low + high) >> 1; |
322 |
T midVal = l.get(mid); |
323 |
int cmp = c.compare(midVal, key); |
324 |
|
325 |
if (cmp < 0) |
326 |
low = mid + 1; |
327 |
else if (cmp > 0) |
328 |
high = mid - 1; |
329 |
else |
330 |
return mid; // key found |
331 |
} |
332 |
return -(low + 1); // key not found |
333 |
} |
334 |
|
335 |
private static <T> int iteratorBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) { |
336 |
int low = 0; |
337 |
int high = l.size()-1; |
338 |
ListIterator<? extends T> i = l.listIterator(); |
339 |
|
340 |
while (low <= high) { |
341 |
int mid = (low + high) >> 1; |
342 |
T midVal = get(i, mid); |
343 |
int cmp = c.compare(midVal, key); |
344 |
|
345 |
if (cmp < 0) |
346 |
low = mid + 1; |
347 |
else if (cmp > 0) |
348 |
high = mid - 1; |
349 |
else |
350 |
return mid; // key found |
351 |
} |
352 |
return -(low + 1); // key not found |
353 |
} |
354 |
|
355 |
private interface SelfComparable extends Comparable<SelfComparable> {} |
356 |
|
357 |
|
358 |
/** |
359 |
* Reverses the order of the elements in the specified list.<p> |
360 |
* |
361 |
* This method runs in linear time. |
362 |
* |
363 |
* @param list the list whose elements are to be reversed. |
364 |
* @throws UnsupportedOperationException if the specified list or |
365 |
* its list-iterator does not support the <tt>set</tt> operation. |
366 |
*/ |
367 |
public static void reverse(List<?> list) { |
368 |
int size = list.size(); |
369 |
if (size < REVERSE_THRESHOLD || list instanceof RandomAccess) { |
370 |
for (int i=0, mid=size>>1, j=size-1; i<mid; i++, j--) |
371 |
swap(list, i, j); |
372 |
} else { |
373 |
ListIterator fwd = list.listIterator(); |
374 |
ListIterator rev = list.listIterator(size); |
375 |
for (int i=0, mid=list.size()>>1; i<mid; i++) { |
376 |
Object tmp = fwd.next(); |
377 |
fwd.set(rev.previous()); |
378 |
rev.set(tmp); |
379 |
} |
380 |
} |
381 |
} |
382 |
|
383 |
/** |
384 |
* Randomly permutes the specified list using a default source of |
385 |
* randomness. All permutations occur with approximately equal |
386 |
* likelihood.<p> |
387 |
* |
388 |
* The hedge "approximately" is used in the foregoing description because |
389 |
* default source of randomness is only approximately an unbiased source |
390 |
* of independently chosen bits. If it were a perfect source of randomly |
391 |
* chosen bits, then the algorithm would choose permutations with perfect |
392 |
* uniformity.<p> |
393 |
* |
394 |
* This implementation traverses the list backwards, from the last element |
395 |
* up to the second, repeatedly swapping a randomly selected element into |
396 |
* the "current position". Elements are randomly selected from the |
397 |
* portion of the list that runs from the first element to the current |
398 |
* position, inclusive.<p> |
399 |
* |
400 |
* This method runs in linear time. If the specified list does not |
401 |
* implement the {@link RandomAccess} interface and is large, this |
402 |
* implementation dumps the specified list into an array before shuffling |
403 |
* it, and dumps the shuffled array back into the list. This avoids the |
404 |
* quadratic behavior that would result from shuffling a "sequential |
405 |
* access" list in place. |
406 |
* |
407 |
* @param list the list to be shuffled. |
408 |
* @throws UnsupportedOperationException if the specified list or |
409 |
* its list-iterator does not support the <tt>set</tt> operation. |
410 |
*/ |
411 |
public static void shuffle(List<?> list) { |
412 |
if (r == null) { |
413 |
r = new Random(); |
414 |
} |
415 |
shuffle(list, r); |
416 |
} |
417 |
private static Random r; |
418 |
|
419 |
/** |
420 |
* Randomly permute the specified list using the specified source of |
421 |
* randomness. All permutations occur with equal likelihood |
422 |
* assuming that the source of randomness is fair.<p> |
423 |
* |
424 |
* This implementation traverses the list backwards, from the last element |
425 |
* up to the second, repeatedly swapping a randomly selected element into |
426 |
* the "current position". Elements are randomly selected from the |
427 |
* portion of the list that runs from the first element to the current |
428 |
* position, inclusive.<p> |
429 |
* |
430 |
* This method runs in linear time. If the specified list does not |
431 |
* implement the {@link RandomAccess} interface and is large, this |
432 |
* implementation dumps the specified list into an array before shuffling |
433 |
* it, and dumps the shuffled array back into the list. This avoids the |
434 |
* quadratic behavior that would result from shuffling a "sequential |
435 |
* access" list in place. |
436 |
* |
437 |
* @param list the list to be shuffled. |
438 |
* @param rnd the source of randomness to use to shuffle the list. |
439 |
* @throws UnsupportedOperationException if the specified list or its |
440 |
* list-iterator does not support the <tt>set</tt> operation. |
441 |
*/ |
442 |
public static void shuffle(List<?> list, Random rnd) { |
443 |
int size = list.size(); |
444 |
if (size < SHUFFLE_THRESHOLD || list instanceof RandomAccess) { |
445 |
for (int i=size; i>1; i--) |
446 |
swap(list, i-1, rnd.nextInt(i)); |
447 |
} else { |
448 |
Object arr[] = list.toArray(); |
449 |
|
450 |
// Shuffle array |
451 |
for (int i=size; i>1; i--) |
452 |
swap(arr, i-1, rnd.nextInt(i)); |
453 |
|
454 |
// Dump array back into list |
455 |
ListIterator it = list.listIterator(); |
456 |
for (int i=0; i<arr.length; i++) { |
457 |
it.next(); |
458 |
it.set(arr[i]); |
459 |
} |
460 |
} |
461 |
} |
462 |
|
463 |
/** |
464 |
* Swaps the elements at the specified positions in the specified list. |
465 |
* (If the specified positions are equal, invoking this method leaves |
466 |
* the list unchanged.) |
467 |
* |
468 |
* @param list The list in which to swap elements. |
469 |
* @param i the index of one element to be swapped. |
470 |
* @param j the index of the other element to be swapped. |
471 |
* @throws IndexOutOfBoundsException if either <tt>i</tt> or <tt>j</tt> |
472 |
* is out of range (i < 0 || i >= list.size() |
473 |
* || j < 0 || j >= list.size()). |
474 |
* @since 1.4 |
475 |
*/ |
476 |
public static void swap(List<?> list, int i, int j) { |
477 |
final List l = list; |
478 |
l.set(i, l.set(j, l.get(i))); |
479 |
} |
480 |
|
481 |
/** |
482 |
* Swaps the two specified elements in the specified array. |
483 |
*/ |
484 |
private static void swap(Object[] arr, int i, int j) { |
485 |
Object tmp = arr[i]; |
486 |
arr[i] = arr[j]; |
487 |
arr[j] = tmp; |
488 |
} |
489 |
|
490 |
/** |
491 |
* Replaces all of the elements of the specified list with the specified |
492 |
* element. <p> |
493 |
* |
494 |
* This method runs in linear time. |
495 |
* |
496 |
* @param list the list to be filled with the specified element. |
497 |
* @param obj The element with which to fill the specified list. |
498 |
* @throws UnsupportedOperationException if the specified list or its |
499 |
* list-iterator does not support the <tt>set</tt> operation. |
500 |
*/ |
501 |
public static <T> void fill(List<? super T> list, T obj) { |
502 |
int size = list.size(); |
503 |
|
504 |
if (size < FILL_THRESHOLD || list instanceof RandomAccess) { |
505 |
for (int i=0; i<size; i++) |
506 |
list.set(i, obj); |
507 |
} else { |
508 |
ListIterator<? super T> itr = list.listIterator(); |
509 |
for (int i=0; i<size; i++) { |
510 |
itr.next(); |
511 |
itr.set(obj); |
512 |
} |
513 |
} |
514 |
} |
515 |
|
516 |
/** |
517 |
* Copies all of the elements from one list into another. After the |
518 |
* operation, the index of each copied element in the destination list |
519 |
* will be identical to its index in the source list. The destination |
520 |
* list must be at least as long as the source list. If it is longer, the |
521 |
* remaining elements in the destination list are unaffected. <p> |
522 |
* |
523 |
* This method runs in linear time. |
524 |
* |
525 |
* @param dest The destination list. |
526 |
* @param src The source list. |
527 |
* @throws IndexOutOfBoundsException if the destination list is too small |
528 |
* to contain the entire source List. |
529 |
* @throws UnsupportedOperationException if the destination list's |
530 |
* list-iterator does not support the <tt>set</tt> operation. |
531 |
*/ |
532 |
public static <T> void copy(List<? super T> dest, List<? extends T> src) { |
533 |
int srcSize = src.size(); |
534 |
if (srcSize > dest.size()) |
535 |
throw new IndexOutOfBoundsException("Source does not fit in dest"); |
536 |
|
537 |
if (srcSize < COPY_THRESHOLD || |
538 |
(src instanceof RandomAccess && dest instanceof RandomAccess)) { |
539 |
for (int i=0; i<srcSize; i++) |
540 |
dest.set(i, src.get(i)); |
541 |
} else { |
542 |
ListIterator<? super T> di=dest.listIterator(); |
543 |
ListIterator<? extends T> si=src.listIterator(); |
544 |
for (int i=0; i<srcSize; i++) { |
545 |
di.next(); |
546 |
di.set(si.next()); |
547 |
} |
548 |
} |
549 |
} |
550 |
|
551 |
/** |
552 |
* Returns the minimum element of the given collection, according to the |
553 |
* <i>natural ordering</i> of its elements. All elements in the |
554 |
* collection must implement the <tt>Comparable</tt> interface. |
555 |
* Furthermore, all elements in the collection must be <i>mutually |
556 |
* comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a |
557 |
* <tt>ClassCastException</tt> for any elements <tt>e1</tt> and |
558 |
* <tt>e2</tt> in the collection).<p> |
559 |
* |
560 |
* This method iterates over the entire collection, hence it requires |
561 |
* time proportional to the size of the collection. |
562 |
* |
563 |
* @param coll the collection whose minimum element is to be determined. |
564 |
* @return the minimum element of the given collection, according |
565 |
* to the <i>natural ordering</i> of its elements. |
566 |
* @throws ClassCastException if the collection contains elements that are |
567 |
* not <i>mutually comparable</i> (for example, strings and |
568 |
* integers). |
569 |
* @throws NoSuchElementException if the collection is empty. |
570 |
* @see Comparable |
571 |
*/ |
572 |
public static <T extends Object & Comparable<? super T>> T min(Collection<? extends T> coll) { |
573 |
Iterator<? extends T> i = coll.iterator(); |
574 |
T candidate = i.next(); |
575 |
|
576 |
while (i.hasNext()) { |
577 |
T next = i.next(); |
578 |
if (next.compareTo(candidate) < 0) |
579 |
candidate = next; |
580 |
} |
581 |
return candidate; |
582 |
} |
583 |
|
584 |
/** |
585 |
* Returns the minimum element of the given collection, according to the |
586 |
* order induced by the specified comparator. All elements in the |
587 |
* collection must be <i>mutually comparable</i> by the specified |
588 |
* comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a |
589 |
* <tt>ClassCastException</tt> for any elements <tt>e1</tt> and |
590 |
* <tt>e2</tt> in the collection).<p> |
591 |
* |
592 |
* This method iterates over the entire collection, hence it requires |
593 |
* time proportional to the size of the collection. |
594 |
* |
595 |
* @param coll the collection whose minimum element is to be determined. |
596 |
* @param comp the comparator with which to determine the minimum element. |
597 |
* A <tt>null</tt> value indicates that the elements' <i>natural |
598 |
* ordering</i> should be used. |
599 |
* @return the minimum element of the given collection, according |
600 |
* to the specified comparator. |
601 |
* @throws ClassCastException if the collection contains elements that are |
602 |
* not <i>mutually comparable</i> using the specified comparator. |
603 |
* @throws NoSuchElementException if the collection is empty. |
604 |
* @see Comparable |
605 |
*/ |
606 |
public static <T> T min(Collection<? extends T> coll, Comparator<? super T> comp) { |
607 |
if (comp==null) |
608 |
return (T)min((Collection<SelfComparable>) (Collection) coll); |
609 |
|
610 |
Iterator<? extends T> i = coll.iterator(); |
611 |
T candidate = i.next(); |
612 |
|
613 |
while (i.hasNext()) { |
614 |
T next = i.next(); |
615 |
if (comp.compare(next, candidate) < 0) |
616 |
candidate = next; |
617 |
} |
618 |
return candidate; |
619 |
} |
620 |
|
621 |
/** |
622 |
* Returns the maximum element of the given collection, according to the |
623 |
* <i>natural ordering</i> of its elements. All elements in the |
624 |
* collection must implement the <tt>Comparable</tt> interface. |
625 |
* Furthermore, all elements in the collection must be <i>mutually |
626 |
* comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a |
627 |
* <tt>ClassCastException</tt> for any elements <tt>e1</tt> and |
628 |
* <tt>e2</tt> in the collection).<p> |
629 |
* |
630 |
* This method iterates over the entire collection, hence it requires |
631 |
* time proportional to the size of the collection. |
632 |
* |
633 |
* @param coll the collection whose maximum element is to be determined. |
634 |
* @return the maximum element of the given collection, according |
635 |
* to the <i>natural ordering</i> of its elements. |
636 |
* @throws ClassCastException if the collection contains elements that are |
637 |
* not <i>mutually comparable</i> (for example, strings and |
638 |
* integers). |
639 |
* @throws NoSuchElementException if the collection is empty. |
640 |
* @see Comparable |
641 |
*/ |
642 |
public static <T extends Object & Comparable<? super T>> T max(Collection<? extends T> coll) { |
643 |
Iterator<? extends T> i = coll.iterator(); |
644 |
T candidate = i.next(); |
645 |
|
646 |
while (i.hasNext()) { |
647 |
T next = i.next(); |
648 |
if (next.compareTo(candidate) > 0) |
649 |
candidate = next; |
650 |
} |
651 |
return candidate; |
652 |
} |
653 |
|
654 |
/** |
655 |
* Returns the maximum element of the given collection, according to the |
656 |
* order induced by the specified comparator. All elements in the |
657 |
* collection must be <i>mutually comparable</i> by the specified |
658 |
* comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a |
659 |
* <tt>ClassCastException</tt> for any elements <tt>e1</tt> and |
660 |
* <tt>e2</tt> in the collection).<p> |
661 |
* |
662 |
* This method iterates over the entire collection, hence it requires |
663 |
* time proportional to the size of the collection. |
664 |
* |
665 |
* @param coll the collection whose maximum element is to be determined. |
666 |
* @param comp the comparator with which to determine the maximum element. |
667 |
* A <tt>null</tt> value indicates that the elements' <i>natural |
668 |
* ordering</i> should be used. |
669 |
* @return the maximum element of the given collection, according |
670 |
* to the specified comparator. |
671 |
* @throws ClassCastException if the collection contains elements that are |
672 |
* not <i>mutually comparable</i> using the specified comparator. |
673 |
* @throws NoSuchElementException if the collection is empty. |
674 |
* @see Comparable |
675 |
*/ |
676 |
public static <T> T max(Collection<? extends T> coll, Comparator<? super T> comp) { |
677 |
if (comp==null) |
678 |
return (T)max((Collection<SelfComparable>) (Collection) coll); |
679 |
|
680 |
Iterator<? extends T> i = coll.iterator(); |
681 |
T candidate = i.next(); |
682 |
|
683 |
while (i.hasNext()) { |
684 |
T next = i.next(); |
685 |
if (comp.compare(next, candidate) > 0) |
686 |
candidate = next; |
687 |
} |
688 |
return candidate; |
689 |
} |
690 |
|
691 |
/** |
692 |
* Rotates the elements in the specified list by the specified distance. |
693 |
* After calling this method, the element at index <tt>i</tt> will be |
694 |
* the element previously at index <tt>(i - distance)</tt> mod |
695 |
* <tt>list.size()</tt>, for all values of <tt>i</tt> between <tt>0</tt> |
696 |
* and <tt>list.size()-1</tt>, inclusive. (This method has no effect on |
697 |
* the size of the list.) |
698 |
* |
699 |
* <p>For example, suppose <tt>list</tt> comprises<tt> [t, a, n, k, s]</tt>. |
700 |
* After invoking <tt>Collections.rotate(list, 1)</tt> (or |
701 |
* <tt>Collections.rotate(list, -4)</tt>), <tt>list</tt> will comprise |
702 |
* <tt>[s, t, a, n, k]</tt>. |
703 |
* |
704 |
* <p>Note that this method can usefully be applied to sublists to |
705 |
* move one or more elements within a list while preserving the |
706 |
* order of the remaining elements. For example, the following idiom |
707 |
* moves the element at index <tt>j</tt> forward to position |
708 |
* <tt>k</tt> (which must be greater than or equal to <tt>j</tt>): |
709 |
* <pre> |
710 |
* Collections.rotate(list.subList(j, k+1), -1); |
711 |
* </pre> |
712 |
* To make this concrete, suppose <tt>list</tt> comprises |
713 |
* <tt>[a, b, c, d, e]</tt>. To move the element at index <tt>1</tt> |
714 |
* (<tt>b</tt>) forward two positions, perform the following invocation: |
715 |
* <pre> |
716 |
* Collections.rotate(l.subList(1, 4), -1); |
717 |
* </pre> |
718 |
* The resulting list is <tt>[a, c, d, b, e]</tt>. |
719 |
* |
720 |
* <p>To move more than one element forward, increase the absolute value |
721 |
* of the rotation distance. To move elements backward, use a positive |
722 |
* shift distance. |
723 |
* |
724 |
* <p>If the specified list is small or implements the {@link |
725 |
* RandomAccess} interface, this implementation exchanges the first |
726 |
* element into the location it should go, and then repeatedly exchanges |
727 |
* the displaced element into the location it should go until a displaced |
728 |
* element is swapped into the first element. If necessary, the process |
729 |
* is repeated on the second and successive elements, until the rotation |
730 |
* is complete. If the specified list is large and doesn't implement the |
731 |
* <tt>RandomAccess</tt> interface, this implementation breaks the |
732 |
* list into two sublist views around index <tt>-distance mod size</tt>. |
733 |
* Then the {@link #reverse(List)} method is invoked on each sublist view, |
734 |
* and finally it is invoked on the entire list. For a more complete |
735 |
* description of both algorithms, see Section 2.3 of Jon Bentley's |
736 |
* <i>Programming Pearls</i> (Addison-Wesley, 1986). |
737 |
* |
738 |
* @param list the list to be rotated. |
739 |
* @param distance the distance to rotate the list. There are no |
740 |
* constraints on this value; it may be zero, negative, or |
741 |
* greater than <tt>list.size()</tt>. |
742 |
* @throws UnsupportedOperationException if the specified list or |
743 |
* its list-iterator does not support the <tt>set</tt> operation. |
744 |
* @since 1.4 |
745 |
*/ |
746 |
public static void rotate(List<?> list, int distance) { |
747 |
if (list instanceof RandomAccess || list.size() < ROTATE_THRESHOLD) |
748 |
rotate1((List)list, distance); |
749 |
else |
750 |
rotate2((List)list, distance); |
751 |
} |
752 |
|
753 |
private static <T> void rotate1(List<T> list, int distance) { |
754 |
int size = list.size(); |
755 |
if (size == 0) |
756 |
return; |
757 |
distance = distance % size; |
758 |
if (distance < 0) |
759 |
distance += size; |
760 |
if (distance == 0) |
761 |
return; |
762 |
|
763 |
for (int cycleStart = 0, nMoved = 0; nMoved != size; cycleStart++) { |
764 |
T displaced = list.get(cycleStart); |
765 |
int i = cycleStart; |
766 |
do { |
767 |
i += distance; |
768 |
if (i >= size) |
769 |
i -= size; |
770 |
displaced = list.set(i, displaced); |
771 |
nMoved ++; |
772 |
} while(i != cycleStart); |
773 |
} |
774 |
} |
775 |
|
776 |
private static void rotate2(List<?> list, int distance) { |
777 |
int size = list.size(); |
778 |
if (size == 0) |
779 |
return; |
780 |
int mid = -distance % size; |
781 |
if (mid < 0) |
782 |
mid += size; |
783 |
if (mid == 0) |
784 |
return; |
785 |
|
786 |
reverse(list.subList(0, mid)); |
787 |
reverse(list.subList(mid, size)); |
788 |
reverse(list); |
789 |
} |
790 |
|
791 |
/** |
792 |
* Replaces all occurrences of one specified value in a list with another. |
793 |
* More formally, replaces with <tt>newVal</tt> each element <tt>e</tt> |
794 |
* in <tt>list</tt> such that |
795 |
* <tt>(oldVal==null ? e==null : oldVal.equals(e))</tt>. |
796 |
* (This method has no effect on the size of the list.) |
797 |
* |
798 |
* @param list the list in which replacement is to occur. |
799 |
* @param oldVal the old value to be replaced. |
800 |
* @param newVal the new value with which <tt>oldVal</tt> is to be |
801 |
* replaced. |
802 |
* @return <tt>true</tt> if <tt>list</tt> contained one or more elements |
803 |
* <tt>e</tt> such that |
804 |
* <tt>(oldVal==null ? e==null : oldVal.equals(e))</tt>. |
805 |
* @throws UnsupportedOperationException if the specified list or |
806 |
* its list-iterator does not support the <tt>set</tt> operation. |
807 |
* @since 1.4 |
808 |
*/ |
809 |
public static <T> boolean replaceAll(List<T> list, T oldVal, T newVal) { |
810 |
boolean result = false; |
811 |
int size = list.size(); |
812 |
if (size < REPLACEALL_THRESHOLD || list instanceof RandomAccess) { |
813 |
if (oldVal==null) { |
814 |
for (int i=0; i<size; i++) { |
815 |
if (list.get(i)==null) { |
816 |
list.set(i, newVal); |
817 |
result = true; |
818 |
} |
819 |
} |
820 |
} else { |
821 |
for (int i=0; i<size; i++) { |
822 |
if (oldVal.equals(list.get(i))) { |
823 |
list.set(i, newVal); |
824 |
result = true; |
825 |
} |
826 |
} |
827 |
} |
828 |
} else { |
829 |
ListIterator<T> itr=list.listIterator(); |
830 |
if (oldVal==null) { |
831 |
for (int i=0; i<size; i++) { |
832 |
if (itr.next()==null) { |
833 |
itr.set(newVal); |
834 |
result = true; |
835 |
} |
836 |
} |
837 |
} else { |
838 |
for (int i=0; i<size; i++) { |
839 |
if (oldVal.equals(itr.next())) { |
840 |
itr.set(newVal); |
841 |
result = true; |
842 |
} |
843 |
} |
844 |
} |
845 |
} |
846 |
return result; |
847 |
} |
848 |
|
849 |
/** |
850 |
* Returns the starting position of the first occurrence of the specified |
851 |
* target list within the specified source list, or -1 if there is no |
852 |
* such occurrence. More formally, returns the lowest index <tt>i</tt> |
853 |
* such that <tt>source.subList(i, i+target.size()).equals(target)</tt>, |
854 |
* or -1 if there is no such index. (Returns -1 if |
855 |
* <tt>target.size() > source.size()</tt>.) |
856 |
* |
857 |
* <p>This implementation uses the "brute force" technique of scanning |
858 |
* over the source list, looking for a match with the target at each |
859 |
* location in turn. |
860 |
* |
861 |
* @param source the list in which to search for the first occurrence |
862 |
* of <tt>target</tt>. |
863 |
* @param target the list to search for as a subList of <tt>source</tt>. |
864 |
* @return the starting position of the first occurrence of the specified |
865 |
* target list within the specified source list, or -1 if there |
866 |
* is no such occurrence. |
867 |
* @since 1.4 |
868 |
*/ |
869 |
public static int indexOfSubList(List<?> source, List<?> target) { |
870 |
int sourceSize = source.size(); |
871 |
int targetSize = target.size(); |
872 |
int maxCandidate = sourceSize - targetSize; |
873 |
|
874 |
if (sourceSize < INDEXOFSUBLIST_THRESHOLD || |
875 |
(source instanceof RandomAccess&&target instanceof RandomAccess)) { |
876 |
nextCand: |
877 |
for (int candidate = 0; candidate <= maxCandidate; candidate++) { |
878 |
for (int i=0, j=candidate; i<targetSize; i++, j++) |
879 |
if (!eq(target.get(i), source.get(j))) |
880 |
continue nextCand; // Element mismatch, try next cand |
881 |
return candidate; // All elements of candidate matched target |
882 |
} |
883 |
} else { // Iterator version of above algorithm |
884 |
ListIterator<?> si = source.listIterator(); |
885 |
nextCand: |
886 |
for (int candidate = 0; candidate <= maxCandidate; candidate++) { |
887 |
ListIterator<?> ti = target.listIterator(); |
888 |
for (int i=0; i<targetSize; i++) { |
889 |
if (!eq(ti.next(), si.next())) { |
890 |
// Back up source iterator to next candidate |
891 |
for (int j=0; j<i; j++) |
892 |
si.previous(); |
893 |
continue nextCand; |
894 |
} |
895 |
} |
896 |
return candidate; |
897 |
} |
898 |
} |
899 |
return -1; // No candidate matched the target |
900 |
} |
901 |
|
902 |
/** |
903 |
* Returns the starting position of the last occurrence of the specified |
904 |
* target list within the specified source list, or -1 if there is no such |
905 |
* occurrence. More formally, returns the highest index <tt>i</tt> |
906 |
* such that <tt>source.subList(i, i+target.size()).equals(target)</tt>, |
907 |
* or -1 if there is no such index. (Returns -1 if |
908 |
* <tt>target.size() > source.size()</tt>.) |
909 |
* |
910 |
* <p>This implementation uses the "brute force" technique of iterating |
911 |
* over the source list, looking for a match with the target at each |
912 |
* location in turn. |
913 |
* |
914 |
* @param source the list in which to search for the last occurrence |
915 |
* of <tt>target</tt>. |
916 |
* @param target the list to search for as a subList of <tt>source</tt>. |
917 |
* @return the starting position of the last occurrence of the specified |
918 |
* target list within the specified source list, or -1 if there |
919 |
* is no such occurrence. |
920 |
* @since 1.4 |
921 |
*/ |
922 |
public static int lastIndexOfSubList(List<?> source, List<?> target) { |
923 |
int sourceSize = source.size(); |
924 |
int targetSize = target.size(); |
925 |
int maxCandidate = sourceSize - targetSize; |
926 |
|
927 |
if (sourceSize < INDEXOFSUBLIST_THRESHOLD || |
928 |
source instanceof RandomAccess) { // Index access version |
929 |
nextCand: |
930 |
for (int candidate = maxCandidate; candidate >= 0; candidate--) { |
931 |
for (int i=0, j=candidate; i<targetSize; i++, j++) |
932 |
if (!eq(target.get(i), source.get(j))) |
933 |
continue nextCand; // Element mismatch, try next cand |
934 |
return candidate; // All elements of candidate matched target |
935 |
} |
936 |
} else { // Iterator version of above algorithm |
937 |
if (maxCandidate < 0) |
938 |
return -1; |
939 |
ListIterator<?> si = source.listIterator(maxCandidate); |
940 |
nextCand: |
941 |
for (int candidate = maxCandidate; candidate >= 0; candidate--) { |
942 |
ListIterator<?> ti = target.listIterator(); |
943 |
for (int i=0; i<targetSize; i++) { |
944 |
if (!eq(ti.next(), si.next())) { |
945 |
if (candidate != 0) { |
946 |
// Back up source iterator to next candidate |
947 |
for (int j=0; j<=i+1; j++) |
948 |
si.previous(); |
949 |
} |
950 |
continue nextCand; |
951 |
} |
952 |
} |
953 |
return candidate; |
954 |
} |
955 |
} |
956 |
return -1; // No candidate matched the target |
957 |
} |
958 |
|
959 |
|
960 |
// Unmodifiable Wrappers |
961 |
|
962 |
/** |
963 |
* Returns an unmodifiable view of the specified collection. This method |
964 |
* allows modules to provide users with "read-only" access to internal |
965 |
* collections. Query operations on the returned collection "read through" |
966 |
* to the specified collection, and attempts to modify the returned |
967 |
* collection, whether direct or via its iterator, result in an |
968 |
* <tt>UnsupportedOperationException</tt>.<p> |
969 |
* |
970 |
* The returned collection does <i>not</i> pass the hashCode and equals |
971 |
* operations through to the backing collection, but relies on |
972 |
* <tt>Object</tt>'s <tt>equals</tt> and <tt>hashCode</tt> methods. This |
973 |
* is necessary to preserve the contracts of these operations in the case |
974 |
* that the backing collection is a set or a list.<p> |
975 |
* |
976 |
* The returned collection will be serializable if the specified collection |
977 |
* is serializable. |
978 |
* |
979 |
* @param c the collection for which an unmodifiable view is to be |
980 |
* returned. |
981 |
* @return an unmodifiable view of the specified collection. |
982 |
*/ |
983 |
public static <T> Collection<T> unmodifiableCollection(Collection<? extends T> c) { |
984 |
return new UnmodifiableCollection<T>(c); |
985 |
} |
986 |
|
987 |
/** |
988 |
* @serial include |
989 |
*/ |
990 |
static class UnmodifiableCollection<E> implements Collection<E>, Serializable { |
991 |
// use serialVersionUID from JDK 1.2.2 for interoperability |
992 |
private static final long serialVersionUID = 1820017752578914078L; |
993 |
|
994 |
final Collection<? extends E> c; |
995 |
|
996 |
UnmodifiableCollection(Collection<? extends E> c) { |
997 |
if (c==null) |
998 |
throw new NullPointerException(); |
999 |
this.c = c; |
1000 |
} |
1001 |
|
1002 |
public int size() {return c.size();} |
1003 |
public boolean isEmpty() {return c.isEmpty();} |
1004 |
public boolean contains(Object o) {return c.contains(o);} |
1005 |
public Object[] toArray() {return c.toArray();} |
1006 |
public <T> T[] toArray(T[] a) {return c.toArray(a);} |
1007 |
public String toString() {return c.toString();} |
1008 |
|
1009 |
public Iterator<E> iterator() { |
1010 |
return new Iterator<E>() { |
1011 |
Iterator<? extends E> i = c.iterator(); |
1012 |
|
1013 |
public boolean hasNext() {return i.hasNext();} |
1014 |
public E next() {return i.next();} |
1015 |
public void remove() { |
1016 |
throw new UnsupportedOperationException(); |
1017 |
} |
1018 |
}; |
1019 |
} |
1020 |
|
1021 |
public boolean add(E e){ |
1022 |
throw new UnsupportedOperationException(); |
1023 |
} |
1024 |
public boolean remove(Object o) { |
1025 |
throw new UnsupportedOperationException(); |
1026 |
} |
1027 |
|
1028 |
public boolean containsAll(Collection<?> coll) { |
1029 |
return c.containsAll(coll); |
1030 |
} |
1031 |
public boolean addAll(Collection<? extends E> coll) { |
1032 |
throw new UnsupportedOperationException(); |
1033 |
} |
1034 |
public boolean removeAll(Collection<?> coll) { |
1035 |
throw new UnsupportedOperationException(); |
1036 |
} |
1037 |
public boolean retainAll(Collection<?> coll) { |
1038 |
throw new UnsupportedOperationException(); |
1039 |
} |
1040 |
public void clear() { |
1041 |
throw new UnsupportedOperationException(); |
1042 |
} |
1043 |
} |
1044 |
|
1045 |
/** |
1046 |
* Returns an unmodifiable view of the specified set. This method allows |
1047 |
* modules to provide users with "read-only" access to internal sets. |
1048 |
* Query operations on the returned set "read through" to the specified |
1049 |
* set, and attempts to modify the returned set, whether direct or via its |
1050 |
* iterator, result in an <tt>UnsupportedOperationException</tt>.<p> |
1051 |
* |
1052 |
* The returned set will be serializable if the specified set |
1053 |
* is serializable. |
1054 |
* |
1055 |
* @param s the set for which an unmodifiable view is to be returned. |
1056 |
* @return an unmodifiable view of the specified set. |
1057 |
*/ |
1058 |
public static <T> Set<T> unmodifiableSet(Set<? extends T> s) { |
1059 |
return new UnmodifiableSet<T>(s); |
1060 |
} |
1061 |
|
1062 |
/** |
1063 |
* @serial include |
1064 |
*/ |
1065 |
static class UnmodifiableSet<E> extends UnmodifiableCollection<E> |
1066 |
implements Set<E>, Serializable { |
1067 |
private static final long serialVersionUID = -9215047833775013803L; |
1068 |
|
1069 |
UnmodifiableSet(Set<? extends E> s) {super(s);} |
1070 |
public boolean equals(Object o) {return c.equals(o);} |
1071 |
public int hashCode() {return c.hashCode();} |
1072 |
} |
1073 |
|
1074 |
/** |
1075 |
* Returns an unmodifiable view of the specified sorted set. This method |
1076 |
* allows modules to provide users with "read-only" access to internal |
1077 |
* sorted sets. Query operations on the returned sorted set "read |
1078 |
* through" to the specified sorted set. Attempts to modify the returned |
1079 |
* sorted set, whether direct, via its iterator, or via its |
1080 |
* <tt>subSet</tt>, <tt>headSet</tt>, or <tt>tailSet</tt> views, result in |
1081 |
* an <tt>UnsupportedOperationException</tt>.<p> |
1082 |
* |
1083 |
* The returned sorted set will be serializable if the specified sorted set |
1084 |
* is serializable. |
1085 |
* |
1086 |
* @param s the sorted set for which an unmodifiable view is to be |
1087 |
* returned. |
1088 |
* @return an unmodifiable view of the specified sorted set. |
1089 |
*/ |
1090 |
public static <T> SortedSet<T> unmodifiableSortedSet(SortedSet<T> s) { |
1091 |
return new UnmodifiableSortedSet<T>(s); |
1092 |
} |
1093 |
|
1094 |
/** |
1095 |
* @serial include |
1096 |
*/ |
1097 |
static class UnmodifiableSortedSet<E> |
1098 |
extends UnmodifiableSet<E> |
1099 |
implements SortedSet<E>, Serializable { |
1100 |
private static final long serialVersionUID = -4929149591599911165L; |
1101 |
private final SortedSet<E> ss; |
1102 |
|
1103 |
UnmodifiableSortedSet(SortedSet<E> s) {super(s); ss = s;} |
1104 |
|
1105 |
public Comparator<? super E> comparator() {return ss.comparator();} |
1106 |
|
1107 |
public SortedSet<E> subSet(E fromElement, E toElement) { |
1108 |
return new UnmodifiableSortedSet<E>(ss.subSet(fromElement,toElement)); |
1109 |
} |
1110 |
public SortedSet<E> headSet(E toElement) { |
1111 |
return new UnmodifiableSortedSet<E>(ss.headSet(toElement)); |
1112 |
} |
1113 |
public SortedSet<E> tailSet(E fromElement) { |
1114 |
return new UnmodifiableSortedSet<E>(ss.tailSet(fromElement)); |
1115 |
} |
1116 |
|
1117 |
public E first() {return ss.first();} |
1118 |
public E last() {return ss.last();} |
1119 |
} |
1120 |
|
1121 |
/** |
1122 |
* Returns an unmodifiable view of the specified list. This method allows |
1123 |
* modules to provide users with "read-only" access to internal |
1124 |
* lists. Query operations on the returned list "read through" to the |
1125 |
* specified list, and attempts to modify the returned list, whether |
1126 |
* direct or via its iterator, result in an |
1127 |
* <tt>UnsupportedOperationException</tt>.<p> |
1128 |
* |
1129 |
* The returned list will be serializable if the specified list |
1130 |
* is serializable. Similarly, the returned list will implement |
1131 |
* {@link RandomAccess} if the specified list does. |
1132 |
* |
1133 |
* @param list the list for which an unmodifiable view is to be returned. |
1134 |
* @return an unmodifiable view of the specified list. |
1135 |
*/ |
1136 |
public static <T> List<T> unmodifiableList(List<? extends T> list) { |
1137 |
return (list instanceof RandomAccess ? |
1138 |
new UnmodifiableRandomAccessList<T>(list) : |
1139 |
new UnmodifiableList<T>(list)); |
1140 |
} |
1141 |
|
1142 |
/** |
1143 |
* @serial include |
1144 |
*/ |
1145 |
static class UnmodifiableList<E> extends UnmodifiableCollection<E> |
1146 |
implements List<E> { |
1147 |
static final long serialVersionUID = -283967356065247728L; |
1148 |
final List<? extends E> list; |
1149 |
|
1150 |
UnmodifiableList(List<? extends E> list) { |
1151 |
super(list); |
1152 |
this.list = list; |
1153 |
} |
1154 |
|
1155 |
public boolean equals(Object o) {return list.equals(o);} |
1156 |
public int hashCode() {return list.hashCode();} |
1157 |
|
1158 |
public E get(int index) {return list.get(index);} |
1159 |
public E set(int index, E element) { |
1160 |
throw new UnsupportedOperationException(); |
1161 |
} |
1162 |
public void add(int index, E element) { |
1163 |
throw new UnsupportedOperationException(); |
1164 |
} |
1165 |
public E remove(int index) { |
1166 |
throw new UnsupportedOperationException(); |
1167 |
} |
1168 |
public int indexOf(Object o) {return list.indexOf(o);} |
1169 |
public int lastIndexOf(Object o) {return list.lastIndexOf(o);} |
1170 |
public boolean addAll(int index, Collection<? extends E> c) { |
1171 |
throw new UnsupportedOperationException(); |
1172 |
} |
1173 |
public ListIterator<E> listIterator() {return listIterator(0);} |
1174 |
|
1175 |
public ListIterator<E> listIterator(final int index) { |
1176 |
return new ListIterator<E>() { |
1177 |
ListIterator<? extends E> i = list.listIterator(index); |
1178 |
|
1179 |
public boolean hasNext() {return i.hasNext();} |
1180 |
public E next() {return i.next();} |
1181 |
public boolean hasPrevious() {return i.hasPrevious();} |
1182 |
public E previous() {return i.previous();} |
1183 |
public int nextIndex() {return i.nextIndex();} |
1184 |
public int previousIndex() {return i.previousIndex();} |
1185 |
|
1186 |
public void remove() { |
1187 |
throw new UnsupportedOperationException(); |
1188 |
} |
1189 |
public void set(E e) { |
1190 |
throw new UnsupportedOperationException(); |
1191 |
} |
1192 |
public void add(E e) { |
1193 |
throw new UnsupportedOperationException(); |
1194 |
} |
1195 |
}; |
1196 |
} |
1197 |
|
1198 |
public List<E> subList(int fromIndex, int toIndex) { |
1199 |
return new UnmodifiableList<E>(list.subList(fromIndex, toIndex)); |
1200 |
} |
1201 |
|
1202 |
/** |
1203 |
* UnmodifiableRandomAccessList instances are serialized as |
1204 |
* UnmodifiableList instances to allow them to be deserialized |
1205 |
* in pre-1.4 JREs (which do not have UnmodifiableRandomAccessList). |
1206 |
* This method inverts the transformation. As a beneficial |
1207 |
* side-effect, it also grafts the RandomAccess marker onto |
1208 |
* UnmodifiableList instances that were serialized in pre-1.4 JREs. |
1209 |
* |
1210 |
* Note: Unfortunately, UnmodifiableRandomAccessList instances |
1211 |
* serialized in 1.4.1 and deserialized in 1.4 will become |
1212 |
* UnmodifiableList instances, as this method was missing in 1.4. |
1213 |
*/ |
1214 |
private Object readResolve() { |
1215 |
return (list instanceof RandomAccess |
1216 |
? new UnmodifiableRandomAccessList<E>(list) |
1217 |
: this); |
1218 |
} |
1219 |
} |
1220 |
|
1221 |
/** |
1222 |
* @serial include |
1223 |
*/ |
1224 |
static class UnmodifiableRandomAccessList<E> extends UnmodifiableList<E> |
1225 |
implements RandomAccess |
1226 |
{ |
1227 |
UnmodifiableRandomAccessList(List<? extends E> list) { |
1228 |
super(list); |
1229 |
} |
1230 |
|
1231 |
public List<E> subList(int fromIndex, int toIndex) { |
1232 |
return new UnmodifiableRandomAccessList<E>( |
1233 |
list.subList(fromIndex, toIndex)); |
1234 |
} |
1235 |
|
1236 |
private static final long serialVersionUID = -2542308836966382001L; |
1237 |
|
1238 |
/** |
1239 |
* Allows instances to be deserialized in pre-1.4 JREs (which do |
1240 |
* not have UnmodifiableRandomAccessList). UnmodifiableList has |
1241 |
* a readResolve method that inverts this transformation upon |
1242 |
* deserialization. |
1243 |
*/ |
1244 |
private Object writeReplace() { |
1245 |
return new UnmodifiableList<E>(list); |
1246 |
} |
1247 |
} |
1248 |
|
1249 |
/** |
1250 |
* Returns an unmodifiable view of the specified map. This method |
1251 |
* allows modules to provide users with "read-only" access to internal |
1252 |
* maps. Query operations on the returned map "read through" |
1253 |
* to the specified map, and attempts to modify the returned |
1254 |
* map, whether direct or via its collection views, result in an |
1255 |
* <tt>UnsupportedOperationException</tt>.<p> |
1256 |
* |
1257 |
* The returned map will be serializable if the specified map |
1258 |
* is serializable. |
1259 |
* |
1260 |
* @param m the map for which an unmodifiable view is to be returned. |
1261 |
* @return an unmodifiable view of the specified map. |
1262 |
*/ |
1263 |
public static <K,V> Map<K,V> unmodifiableMap(Map<? extends K, ? extends V> m) { |
1264 |
return new UnmodifiableMap<K,V>(m); |
1265 |
} |
1266 |
|
1267 |
/** |
1268 |
* @serial include |
1269 |
*/ |
1270 |
private static class UnmodifiableMap<K,V> implements Map<K,V>, Serializable { |
1271 |
// use serialVersionUID from JDK 1.2.2 for interoperability |
1272 |
private static final long serialVersionUID = -1034234728574286014L; |
1273 |
|
1274 |
private final Map<? extends K, ? extends V> m; |
1275 |
|
1276 |
UnmodifiableMap(Map<? extends K, ? extends V> m) { |
1277 |
if (m==null) |
1278 |
throw new NullPointerException(); |
1279 |
this.m = m; |
1280 |
} |
1281 |
|
1282 |
public int size() {return m.size();} |
1283 |
public boolean isEmpty() {return m.isEmpty();} |
1284 |
public boolean containsKey(Object key) {return m.containsKey(key);} |
1285 |
public boolean containsValue(Object val) {return m.containsValue(val);} |
1286 |
public V get(Object key) {return m.get(key);} |
1287 |
|
1288 |
public V put(K key, V value) { |
1289 |
throw new UnsupportedOperationException(); |
1290 |
} |
1291 |
public V remove(Object key) { |
1292 |
throw new UnsupportedOperationException(); |
1293 |
} |
1294 |
public void putAll(Map<? extends K, ? extends V> t) { |
1295 |
throw new UnsupportedOperationException(); |
1296 |
} |
1297 |
public void clear() { |
1298 |
throw new UnsupportedOperationException(); |
1299 |
} |
1300 |
|
1301 |
private transient Set<K> keySet = null; |
1302 |
private transient Set<Map.Entry<K,V>> entrySet = null; |
1303 |
private transient Collection<V> values = null; |
1304 |
|
1305 |
public Set<K> keySet() { |
1306 |
if (keySet==null) |
1307 |
keySet = unmodifiableSet(m.keySet()); |
1308 |
return keySet; |
1309 |
} |
1310 |
|
1311 |
public Set<Map.Entry<K,V>> entrySet() { |
1312 |
if (entrySet==null) |
1313 |
entrySet = new UnmodifiableEntrySet<K,V>(m.entrySet()); |
1314 |
return entrySet; |
1315 |
} |
1316 |
|
1317 |
public Collection<V> values() { |
1318 |
if (values==null) |
1319 |
values = unmodifiableCollection(m.values()); |
1320 |
return values; |
1321 |
} |
1322 |
|
1323 |
public boolean equals(Object o) {return m.equals(o);} |
1324 |
public int hashCode() {return m.hashCode();} |
1325 |
public String toString() {return m.toString();} |
1326 |
|
1327 |
/** |
1328 |
* We need this class in addition to UnmodifiableSet as |
1329 |
* Map.Entries themselves permit modification of the backing Map |
1330 |
* via their setValue operation. This class is subtle: there are |
1331 |
* many possible attacks that must be thwarted. |
1332 |
* |
1333 |
* @serial include |
1334 |
*/ |
1335 |
static class UnmodifiableEntrySet<K,V> |
1336 |
extends UnmodifiableSet<Map.Entry<K,V>> { |
1337 |
private static final long serialVersionUID = 7854390611657943733L; |
1338 |
|
1339 |
UnmodifiableEntrySet(Set<? extends Map.Entry<? extends K, ? extends V>> s) { |
1340 |
super((Set)s); |
1341 |
} |
1342 |
public Iterator<Map.Entry<K,V>> iterator() { |
1343 |
return new Iterator<Map.Entry<K,V>>() { |
1344 |
Iterator<? extends Map.Entry<? extends K, ? extends V>> i = c.iterator(); |
1345 |
|
1346 |
public boolean hasNext() { |
1347 |
return i.hasNext(); |
1348 |
} |
1349 |
public Map.Entry<K,V> next() { |
1350 |
return new UnmodifiableEntry<K,V>(i.next()); |
1351 |
} |
1352 |
public void remove() { |
1353 |
throw new UnsupportedOperationException(); |
1354 |
} |
1355 |
}; |
1356 |
} |
1357 |
|
1358 |
public Object[] toArray() { |
1359 |
Object[] a = c.toArray(); |
1360 |
for (int i=0; i<a.length; i++) |
1361 |
a[i] = new UnmodifiableEntry<K,V>((Map.Entry<K,V>)a[i]); |
1362 |
return a; |
1363 |
} |
1364 |
|
1365 |
public <T> T[] toArray(T[] a) { |
1366 |
// We don't pass a to c.toArray, to avoid window of |
1367 |
// vulnerability wherein an unscrupulous multithreaded client |
1368 |
// could get his hands on raw (unwrapped) Entries from c. |
1369 |
Object[] arr = c.toArray(a.length==0 ? a : Arrays.copyOf(a, 0)); |
1370 |
|
1371 |
for (int i=0; i<arr.length; i++) |
1372 |
arr[i] = new UnmodifiableEntry<K,V>((Map.Entry<K,V>)arr[i]); |
1373 |
|
1374 |
if (arr.length > a.length) |
1375 |
return (T[])arr; |
1376 |
|
1377 |
System.arraycopy(arr, 0, a, 0, arr.length); |
1378 |
if (a.length > arr.length) |
1379 |
a[arr.length] = null; |
1380 |
return a; |
1381 |
} |
1382 |
|
1383 |
/** |
1384 |
* This method is overridden to protect the backing set against |
1385 |
* an object with a nefarious equals function that senses |
1386 |
* that the equality-candidate is Map.Entry and calls its |
1387 |
* setValue method. |
1388 |
*/ |
1389 |
public boolean contains(Object o) { |
1390 |
if (!(o instanceof Map.Entry)) |
1391 |
return false; |
1392 |
return c.contains(new UnmodifiableEntry<K,V>((Map.Entry<K,V>) o)); |
1393 |
} |
1394 |
|
1395 |
/** |
1396 |
* The next two methods are overridden to protect against |
1397 |
* an unscrupulous List whose contains(Object o) method senses |
1398 |
* when o is a Map.Entry, and calls o.setValue. |
1399 |
*/ |
1400 |
public boolean containsAll(Collection<?> coll) { |
1401 |
Iterator<?> e = coll.iterator(); |
1402 |
while (e.hasNext()) |
1403 |
if (!contains(e.next())) // Invokes safe contains() above |
1404 |
return false; |
1405 |
return true; |
1406 |
} |
1407 |
public boolean equals(Object o) { |
1408 |
if (o == this) |
1409 |
return true; |
1410 |
|
1411 |
if (!(o instanceof Set)) |
1412 |
return false; |
1413 |
Set s = (Set) o; |
1414 |
if (s.size() != c.size()) |
1415 |
return false; |
1416 |
return containsAll(s); // Invokes safe containsAll() above |
1417 |
} |
1418 |
|
1419 |
/** |
1420 |
* This "wrapper class" serves two purposes: it prevents |
1421 |
* the client from modifying the backing Map, by short-circuiting |
1422 |
* the setValue method, and it protects the backing Map against |
1423 |
* an ill-behaved Map.Entry that attempts to modify another |
1424 |
* Map Entry when asked to perform an equality check. |
1425 |
*/ |
1426 |
private static class UnmodifiableEntry<K,V> implements Map.Entry<K,V> { |
1427 |
private Map.Entry<? extends K, ? extends V> e; |
1428 |
|
1429 |
UnmodifiableEntry(Map.Entry<? extends K, ? extends V> e) {this.e = e;} |
1430 |
|
1431 |
public K getKey() {return e.getKey();} |
1432 |
public V getValue() {return e.getValue();} |
1433 |
public V setValue(V value) { |
1434 |
throw new UnsupportedOperationException(); |
1435 |
} |
1436 |
public int hashCode() {return e.hashCode();} |
1437 |
public boolean equals(Object o) { |
1438 |
if (!(o instanceof Map.Entry)) |
1439 |
return false; |
1440 |
Map.Entry t = (Map.Entry)o; |
1441 |
return eq(e.getKey(), t.getKey()) && |
1442 |
eq(e.getValue(), t.getValue()); |
1443 |
} |
1444 |
public String toString() {return e.toString();} |
1445 |
} |
1446 |
} |
1447 |
} |
1448 |
|
1449 |
/** |
1450 |
* Returns an unmodifiable view of the specified sorted map. This method |
1451 |
* allows modules to provide users with "read-only" access to internal |
1452 |
* sorted maps. Query operations on the returned sorted map "read through" |
1453 |
* to the specified sorted map. Attempts to modify the returned |
1454 |
* sorted map, whether direct, via its collection views, or via its |
1455 |
* <tt>subMap</tt>, <tt>headMap</tt>, or <tt>tailMap</tt> views, result in |
1456 |
* an <tt>UnsupportedOperationException</tt>.<p> |
1457 |
* |
1458 |
* The returned sorted map will be serializable if the specified sorted map |
1459 |
* is serializable. |
1460 |
* |
1461 |
* @param m the sorted map for which an unmodifiable view is to be |
1462 |
* returned. |
1463 |
* @return an unmodifiable view of the specified sorted map. |
1464 |
*/ |
1465 |
public static <K,V> SortedMap<K,V> unmodifiableSortedMap(SortedMap<K, ? extends V> m) { |
1466 |
return new UnmodifiableSortedMap<K,V>(m); |
1467 |
} |
1468 |
|
1469 |
/** |
1470 |
* @serial include |
1471 |
*/ |
1472 |
static class UnmodifiableSortedMap<K,V> |
1473 |
extends UnmodifiableMap<K,V> |
1474 |
implements SortedMap<K,V>, Serializable { |
1475 |
private static final long serialVersionUID = -8806743815996713206L; |
1476 |
|
1477 |
private final SortedMap<K, ? extends V> sm; |
1478 |
|
1479 |
UnmodifiableSortedMap(SortedMap<K, ? extends V> m) {super(m); sm = m;} |
1480 |
|
1481 |
public Comparator<? super K> comparator() {return sm.comparator();} |
1482 |
|
1483 |
public SortedMap<K,V> subMap(K fromKey, K toKey) { |
1484 |
return new UnmodifiableSortedMap<K,V>(sm.subMap(fromKey, toKey)); |
1485 |
} |
1486 |
public SortedMap<K,V> headMap(K toKey) { |
1487 |
return new UnmodifiableSortedMap<K,V>(sm.headMap(toKey)); |
1488 |
} |
1489 |
public SortedMap<K,V> tailMap(K fromKey) { |
1490 |
return new UnmodifiableSortedMap<K,V>(sm.tailMap(fromKey)); |
1491 |
} |
1492 |
|
1493 |
public K firstKey() {return sm.firstKey();} |
1494 |
public K lastKey() {return sm.lastKey();} |
1495 |
} |
1496 |
|
1497 |
|
1498 |
// Synch Wrappers |
1499 |
|
1500 |
/** |
1501 |
* Returns a synchronized (thread-safe) collection backed by the specified |
1502 |
* collection. In order to guarantee serial access, it is critical that |
1503 |
* <strong>all</strong> access to the backing collection is accomplished |
1504 |
* through the returned collection.<p> |
1505 |
* |
1506 |
* It is imperative that the user manually synchronize on the returned |
1507 |
* collection when iterating over it: |
1508 |
* <pre> |
1509 |
* Collection c = Collections.synchronizedCollection(myCollection); |
1510 |
* ... |
1511 |
* synchronized(c) { |
1512 |
* Iterator i = c.iterator(); // Must be in the synchronized block |
1513 |
* while (i.hasNext()) |
1514 |
* foo(i.next()); |
1515 |
* } |
1516 |
* </pre> |
1517 |
* Failure to follow this advice may result in non-deterministic behavior. |
1518 |
* |
1519 |
* <p>The returned collection does <i>not</i> pass the <tt>hashCode</tt> |
1520 |
* and <tt>equals</tt> operations through to the backing collection, but |
1521 |
* relies on <tt>Object</tt>'s equals and hashCode methods. This is |
1522 |
* necessary to preserve the contracts of these operations in the case |
1523 |
* that the backing collection is a set or a list.<p> |
1524 |
* |
1525 |
* The returned collection will be serializable if the specified collection |
1526 |
* is serializable. |
1527 |
* |
1528 |
* @param c the collection to be "wrapped" in a synchronized collection. |
1529 |
* @return a synchronized view of the specified collection. |
1530 |
*/ |
1531 |
public static <T> Collection<T> synchronizedCollection(Collection<T> c) { |
1532 |
return new SynchronizedCollection<T>(c); |
1533 |
} |
1534 |
|
1535 |
static <T> Collection<T> synchronizedCollection(Collection<T> c, Object mutex) { |
1536 |
return new SynchronizedCollection<T>(c, mutex); |
1537 |
} |
1538 |
|
1539 |
/** |
1540 |
* @serial include |
1541 |
*/ |
1542 |
static class SynchronizedCollection<E> implements Collection<E>, Serializable { |
1543 |
// use serialVersionUID from JDK 1.2.2 for interoperability |
1544 |
private static final long serialVersionUID = 3053995032091335093L; |
1545 |
|
1546 |
final Collection<E> c; // Backing Collection |
1547 |
final Object mutex; // Object on which to synchronize |
1548 |
|
1549 |
SynchronizedCollection(Collection<E> c) { |
1550 |
if (c==null) |
1551 |
throw new NullPointerException(); |
1552 |
this.c = c; |
1553 |
mutex = this; |
1554 |
} |
1555 |
SynchronizedCollection(Collection<E> c, Object mutex) { |
1556 |
this.c = c; |
1557 |
this.mutex = mutex; |
1558 |
} |
1559 |
|
1560 |
public int size() { |
1561 |
synchronized(mutex) {return c.size();} |
1562 |
} |
1563 |
public boolean isEmpty() { |
1564 |
synchronized(mutex) {return c.isEmpty();} |
1565 |
} |
1566 |
public boolean contains(Object o) { |
1567 |
synchronized(mutex) {return c.contains(o);} |
1568 |
} |
1569 |
public Object[] toArray() { |
1570 |
synchronized(mutex) {return c.toArray();} |
1571 |
} |
1572 |
public <T> T[] toArray(T[] a) { |
1573 |
synchronized(mutex) {return c.toArray(a);} |
1574 |
} |
1575 |
|
1576 |
public Iterator<E> iterator() { |
1577 |
return c.iterator(); // Must be manually synched by user! |
1578 |
} |
1579 |
|
1580 |
public boolean add(E e) { |
1581 |
synchronized(mutex) {return c.add(e);} |
1582 |
} |
1583 |
public boolean remove(Object o) { |
1584 |
synchronized(mutex) {return c.remove(o);} |
1585 |
} |
1586 |
|
1587 |
public boolean containsAll(Collection<?> coll) { |
1588 |
synchronized(mutex) {return c.containsAll(coll);} |
1589 |
} |
1590 |
public boolean addAll(Collection<? extends E> coll) { |
1591 |
synchronized(mutex) {return c.addAll(coll);} |
1592 |
} |
1593 |
public boolean removeAll(Collection<?> coll) { |
1594 |
synchronized(mutex) {return c.removeAll(coll);} |
1595 |
} |
1596 |
public boolean retainAll(Collection<?> coll) { |
1597 |
synchronized(mutex) {return c.retainAll(coll);} |
1598 |
} |
1599 |
public void clear() { |
1600 |
synchronized(mutex) {c.clear();} |
1601 |
} |
1602 |
public String toString() { |
1603 |
synchronized(mutex) {return c.toString();} |
1604 |
} |
1605 |
private void writeObject(ObjectOutputStream s) throws IOException { |
1606 |
synchronized(mutex) {s.defaultWriteObject();} |
1607 |
} |
1608 |
} |
1609 |
|
1610 |
/** |
1611 |
* Returns a synchronized (thread-safe) set backed by the specified |
1612 |
* set. In order to guarantee serial access, it is critical that |
1613 |
* <strong>all</strong> access to the backing set is accomplished |
1614 |
* through the returned set.<p> |
1615 |
* |
1616 |
* It is imperative that the user manually synchronize on the returned |
1617 |
* set when iterating over it: |
1618 |
* <pre> |
1619 |
* Set s = Collections.synchronizedSet(new HashSet()); |
1620 |
* ... |
1621 |
* synchronized(s) { |
1622 |
* Iterator i = s.iterator(); // Must be in the synchronized block |
1623 |
* while (i.hasNext()) |
1624 |
* foo(i.next()); |
1625 |
* } |
1626 |
* </pre> |
1627 |
* Failure to follow this advice may result in non-deterministic behavior. |
1628 |
* |
1629 |
* <p>The returned set will be serializable if the specified set is |
1630 |
* serializable. |
1631 |
* |
1632 |
* @param s the set to be "wrapped" in a synchronized set. |
1633 |
* @return a synchronized view of the specified set. |
1634 |
*/ |
1635 |
public static <T> Set<T> synchronizedSet(Set<T> s) { |
1636 |
return new SynchronizedSet<T>(s); |
1637 |
} |
1638 |
|
1639 |
static <T> Set<T> synchronizedSet(Set<T> s, Object mutex) { |
1640 |
return new SynchronizedSet<T>(s, mutex); |
1641 |
} |
1642 |
|
1643 |
/** |
1644 |
* @serial include |
1645 |
*/ |
1646 |
static class SynchronizedSet<E> |
1647 |
extends SynchronizedCollection<E> |
1648 |
implements Set<E> { |
1649 |
private static final long serialVersionUID = 487447009682186044L; |
1650 |
|
1651 |
SynchronizedSet(Set<E> s) { |
1652 |
super(s); |
1653 |
} |
1654 |
SynchronizedSet(Set<E> s, Object mutex) { |
1655 |
super(s, mutex); |
1656 |
} |
1657 |
|
1658 |
public boolean equals(Object o) { |
1659 |
synchronized(mutex) {return c.equals(o);} |
1660 |
} |
1661 |
public int hashCode() { |
1662 |
synchronized(mutex) {return c.hashCode();} |
1663 |
} |
1664 |
} |
1665 |
|
1666 |
/** |
1667 |
* Returns a synchronized (thread-safe) sorted set backed by the specified |
1668 |
* sorted set. In order to guarantee serial access, it is critical that |
1669 |
* <strong>all</strong> access to the backing sorted set is accomplished |
1670 |
* through the returned sorted set (or its views).<p> |
1671 |
* |
1672 |
* It is imperative that the user manually synchronize on the returned |
1673 |
* sorted set when iterating over it or any of its <tt>subSet</tt>, |
1674 |
* <tt>headSet</tt>, or <tt>tailSet</tt> views. |
1675 |
* <pre> |
1676 |
* SortedSet s = Collections.synchronizedSortedSet(new TreeSet()); |
1677 |
* ... |
1678 |
* synchronized(s) { |
1679 |
* Iterator i = s.iterator(); // Must be in the synchronized block |
1680 |
* while (i.hasNext()) |
1681 |
* foo(i.next()); |
1682 |
* } |
1683 |
* </pre> |
1684 |
* or: |
1685 |
* <pre> |
1686 |
* SortedSet s = Collections.synchronizedSortedSet(new TreeSet()); |
1687 |
* SortedSet s2 = s.headSet(foo); |
1688 |
* ... |
1689 |
* synchronized(s) { // Note: s, not s2!!! |
1690 |
* Iterator i = s2.iterator(); // Must be in the synchronized block |
1691 |
* while (i.hasNext()) |
1692 |
* foo(i.next()); |
1693 |
* } |
1694 |
* </pre> |
1695 |
* Failure to follow this advice may result in non-deterministic behavior. |
1696 |
* |
1697 |
* <p>The returned sorted set will be serializable if the specified |
1698 |
* sorted set is serializable. |
1699 |
* |
1700 |
* @param s the sorted set to be "wrapped" in a synchronized sorted set. |
1701 |
* @return a synchronized view of the specified sorted set. |
1702 |
*/ |
1703 |
public static <T> SortedSet<T> synchronizedSortedSet(SortedSet<T> s) { |
1704 |
return new SynchronizedSortedSet<T>(s); |
1705 |
} |
1706 |
|
1707 |
/** |
1708 |
* @serial include |
1709 |
*/ |
1710 |
static class SynchronizedSortedSet<E> |
1711 |
extends SynchronizedSet<E> |
1712 |
implements SortedSet<E> |
1713 |
{ |
1714 |
private static final long serialVersionUID = 8695801310862127406L; |
1715 |
|
1716 |
final private SortedSet<E> ss; |
1717 |
|
1718 |
SynchronizedSortedSet(SortedSet<E> s) { |
1719 |
super(s); |
1720 |
ss = s; |
1721 |
} |
1722 |
SynchronizedSortedSet(SortedSet<E> s, Object mutex) { |
1723 |
super(s, mutex); |
1724 |
ss = s; |
1725 |
} |
1726 |
|
1727 |
public Comparator<? super E> comparator() { |
1728 |
synchronized(mutex) {return ss.comparator();} |
1729 |
} |
1730 |
|
1731 |
public SortedSet<E> subSet(E fromElement, E toElement) { |
1732 |
synchronized(mutex) { |
1733 |
return new SynchronizedSortedSet<E>( |
1734 |
ss.subSet(fromElement, toElement), mutex); |
1735 |
} |
1736 |
} |
1737 |
public SortedSet<E> headSet(E toElement) { |
1738 |
synchronized(mutex) { |
1739 |
return new SynchronizedSortedSet<E>(ss.headSet(toElement), mutex); |
1740 |
} |
1741 |
} |
1742 |
public SortedSet<E> tailSet(E fromElement) { |
1743 |
synchronized(mutex) { |
1744 |
return new SynchronizedSortedSet<E>(ss.tailSet(fromElement),mutex); |
1745 |
} |
1746 |
} |
1747 |
|
1748 |
public E first() { |
1749 |
synchronized(mutex) {return ss.first();} |
1750 |
} |
1751 |
public E last() { |
1752 |
synchronized(mutex) {return ss.last();} |
1753 |
} |
1754 |
} |
1755 |
|
1756 |
/** |
1757 |
* Returns a synchronized (thread-safe) list backed by the specified |
1758 |
* list. In order to guarantee serial access, it is critical that |
1759 |
* <strong>all</strong> access to the backing list is accomplished |
1760 |
* through the returned list.<p> |
1761 |
* |
1762 |
* It is imperative that the user manually synchronize on the returned |
1763 |
* list when iterating over it: |
1764 |
* <pre> |
1765 |
* List list = Collections.synchronizedList(new ArrayList()); |
1766 |
* ... |
1767 |
* synchronized(list) { |
1768 |
* Iterator i = list.iterator(); // Must be in synchronized block |
1769 |
* while (i.hasNext()) |
1770 |
* foo(i.next()); |
1771 |
* } |
1772 |
* </pre> |
1773 |
* Failure to follow this advice may result in non-deterministic behavior. |
1774 |
* |
1775 |
* <p>The returned list will be serializable if the specified list is |
1776 |
* serializable. |
1777 |
* |
1778 |
* @param list the list to be "wrapped" in a synchronized list. |
1779 |
* @return a synchronized view of the specified list. |
1780 |
*/ |
1781 |
public static <T> List<T> synchronizedList(List<T> list) { |
1782 |
return (list instanceof RandomAccess ? |
1783 |
new SynchronizedRandomAccessList<T>(list) : |
1784 |
new SynchronizedList<T>(list)); |
1785 |
} |
1786 |
|
1787 |
static <T> List<T> synchronizedList(List<T> list, Object mutex) { |
1788 |
return (list instanceof RandomAccess ? |
1789 |
new SynchronizedRandomAccessList<T>(list, mutex) : |
1790 |
new SynchronizedList<T>(list, mutex)); |
1791 |
} |
1792 |
|
1793 |
/** |
1794 |
* @serial include |
1795 |
*/ |
1796 |
static class SynchronizedList<E> |
1797 |
extends SynchronizedCollection<E> |
1798 |
implements List<E> { |
1799 |
static final long serialVersionUID = -7754090372962971524L; |
1800 |
|
1801 |
final List<E> list; |
1802 |
|
1803 |
SynchronizedList(List<E> list) { |
1804 |
super(list); |
1805 |
this.list = list; |
1806 |
} |
1807 |
SynchronizedList(List<E> list, Object mutex) { |
1808 |
super(list, mutex); |
1809 |
this.list = list; |
1810 |
} |
1811 |
|
1812 |
public boolean equals(Object o) { |
1813 |
synchronized(mutex) {return list.equals(o);} |
1814 |
} |
1815 |
public int hashCode() { |
1816 |
synchronized(mutex) {return list.hashCode();} |
1817 |
} |
1818 |
|
1819 |
public E get(int index) { |
1820 |
synchronized(mutex) {return list.get(index);} |
1821 |
} |
1822 |
public E set(int index, E element) { |
1823 |
synchronized(mutex) {return list.set(index, element);} |
1824 |
} |
1825 |
public void add(int index, E element) { |
1826 |
synchronized(mutex) {list.add(index, element);} |
1827 |
} |
1828 |
public E remove(int index) { |
1829 |
synchronized(mutex) {return list.remove(index);} |
1830 |
} |
1831 |
|
1832 |
public int indexOf(Object o) { |
1833 |
synchronized(mutex) {return list.indexOf(o);} |
1834 |
} |
1835 |
public int lastIndexOf(Object o) { |
1836 |
synchronized(mutex) {return list.lastIndexOf(o);} |
1837 |
} |
1838 |
|
1839 |
public boolean addAll(int index, Collection<? extends E> c) { |
1840 |
synchronized(mutex) {return list.addAll(index, c);} |
1841 |
} |
1842 |
|
1843 |
public ListIterator<E> listIterator() { |
1844 |
return list.listIterator(); // Must be manually synched by user |
1845 |
} |
1846 |
|
1847 |
public ListIterator<E> listIterator(int index) { |
1848 |
return list.listIterator(index); // Must be manually synched by user |
1849 |
} |
1850 |
|
1851 |
public List<E> subList(int fromIndex, int toIndex) { |
1852 |
synchronized(mutex) { |
1853 |
return new SynchronizedList<E>(list.subList(fromIndex, toIndex), |
1854 |
mutex); |
1855 |
} |
1856 |
} |
1857 |
|
1858 |
/** |
1859 |
* SynchronizedRandomAccessList instances are serialized as |
1860 |
* SynchronizedList instances to allow them to be deserialized |
1861 |
* in pre-1.4 JREs (which do not have SynchronizedRandomAccessList). |
1862 |
* This method inverts the transformation. As a beneficial |
1863 |
* side-effect, it also grafts the RandomAccess marker onto |
1864 |
* SynchronizedList instances that were serialized in pre-1.4 JREs. |
1865 |
* |
1866 |
* Note: Unfortunately, SynchronizedRandomAccessList instances |
1867 |
* serialized in 1.4.1 and deserialized in 1.4 will become |
1868 |
* SynchronizedList instances, as this method was missing in 1.4. |
1869 |
*/ |
1870 |
private Object readResolve() { |
1871 |
return (list instanceof RandomAccess |
1872 |
? new SynchronizedRandomAccessList<E>(list) |
1873 |
: this); |
1874 |
} |
1875 |
} |
1876 |
|
1877 |
/** |
1878 |
* @serial include |
1879 |
*/ |
1880 |
static class SynchronizedRandomAccessList<E> |
1881 |
extends SynchronizedList<E> |
1882 |
implements RandomAccess { |
1883 |
|
1884 |
SynchronizedRandomAccessList(List<E> list) { |
1885 |
super(list); |
1886 |
} |
1887 |
|
1888 |
SynchronizedRandomAccessList(List<E> list, Object mutex) { |
1889 |
super(list, mutex); |
1890 |
} |
1891 |
|
1892 |
public List<E> subList(int fromIndex, int toIndex) { |
1893 |
synchronized(mutex) { |
1894 |
return new SynchronizedRandomAccessList<E>( |
1895 |
list.subList(fromIndex, toIndex), mutex); |
1896 |
} |
1897 |
} |
1898 |
|
1899 |
static final long serialVersionUID = 1530674583602358482L; |
1900 |
|
1901 |
/** |
1902 |
* Allows instances to be deserialized in pre-1.4 JREs (which do |
1903 |
* not have SynchronizedRandomAccessList). SynchronizedList has |
1904 |
* a readResolve method that inverts this transformation upon |
1905 |
* deserialization. |
1906 |
*/ |
1907 |
private Object writeReplace() { |
1908 |
return new SynchronizedList<E>(list); |
1909 |
} |
1910 |
} |
1911 |
|
1912 |
/** |
1913 |
* Returns a synchronized (thread-safe) map backed by the specified |
1914 |
* map. In order to guarantee serial access, it is critical that |
1915 |
* <strong>all</strong> access to the backing map is accomplished |
1916 |
* through the returned map.<p> |
1917 |
* |
1918 |
* It is imperative that the user manually synchronize on the returned |
1919 |
* map when iterating over any of its collection views: |
1920 |
* <pre> |
1921 |
* Map m = Collections.synchronizedMap(new HashMap()); |
1922 |
* ... |
1923 |
* Set s = m.keySet(); // Needn't be in synchronized block |
1924 |
* ... |
1925 |
* synchronized(m) { // Synchronizing on m, not s! |
1926 |
* Iterator i = s.iterator(); // Must be in synchronized block |
1927 |
* while (i.hasNext()) |
1928 |
* foo(i.next()); |
1929 |
* } |
1930 |
* </pre> |
1931 |
* Failure to follow this advice may result in non-deterministic behavior. |
1932 |
* |
1933 |
* <p>The returned map will be serializable if the specified map is |
1934 |
* serializable. |
1935 |
* |
1936 |
* @param m the map to be "wrapped" in a synchronized map. |
1937 |
* @return a synchronized view of the specified map. |
1938 |
*/ |
1939 |
public static <K,V> Map<K,V> synchronizedMap(Map<K,V> m) { |
1940 |
return new SynchronizedMap<K,V>(m); |
1941 |
} |
1942 |
|
1943 |
/** |
1944 |
* @serial include |
1945 |
*/ |
1946 |
private static class SynchronizedMap<K,V> |
1947 |
implements Map<K,V>, Serializable { |
1948 |
// use serialVersionUID from JDK 1.2.2 for interoperability |
1949 |
private static final long serialVersionUID = 1978198479659022715L; |
1950 |
|
1951 |
private final Map<K,V> m; // Backing Map |
1952 |
final Object mutex; // Object on which to synchronize |
1953 |
|
1954 |
SynchronizedMap(Map<K,V> m) { |
1955 |
if (m==null) |
1956 |
throw new NullPointerException(); |
1957 |
this.m = m; |
1958 |
mutex = this; |
1959 |
} |
1960 |
|
1961 |
SynchronizedMap(Map<K,V> m, Object mutex) { |
1962 |
this.m = m; |
1963 |
this.mutex = mutex; |
1964 |
} |
1965 |
|
1966 |
public int size() { |
1967 |
synchronized(mutex) {return m.size();} |
1968 |
} |
1969 |
public boolean isEmpty(){ |
1970 |
synchronized(mutex) {return m.isEmpty();} |
1971 |
} |
1972 |
public boolean containsKey(Object key) { |
1973 |
synchronized(mutex) {return m.containsKey(key);} |
1974 |
} |
1975 |
public boolean containsValue(Object value){ |
1976 |
synchronized(mutex) {return m.containsValue(value);} |
1977 |
} |
1978 |
public V get(Object key) { |
1979 |
synchronized(mutex) {return m.get(key);} |
1980 |
} |
1981 |
|
1982 |
public V put(K key, V value) { |
1983 |
synchronized(mutex) {return m.put(key, value);} |
1984 |
} |
1985 |
public V remove(Object key) { |
1986 |
synchronized(mutex) {return m.remove(key);} |
1987 |
} |
1988 |
public void putAll(Map<? extends K, ? extends V> map) { |
1989 |
synchronized(mutex) {m.putAll(map);} |
1990 |
} |
1991 |
public void clear() { |
1992 |
synchronized(mutex) {m.clear();} |
1993 |
} |
1994 |
|
1995 |
private transient Set<K> keySet = null; |
1996 |
private transient Set<Map.Entry<K,V>> entrySet = null; |
1997 |
private transient Collection<V> values = null; |
1998 |
|
1999 |
public Set<K> keySet() { |
2000 |
synchronized(mutex) { |
2001 |
if (keySet==null) |
2002 |
keySet = new SynchronizedSet<K>(m.keySet(), mutex); |
2003 |
return keySet; |
2004 |
} |
2005 |
} |
2006 |
|
2007 |
public Set<Map.Entry<K,V>> entrySet() { |
2008 |
synchronized(mutex) { |
2009 |
if (entrySet==null) |
2010 |
entrySet = new SynchronizedSet<Map.Entry<K,V>>(m.entrySet(), mutex); |
2011 |
return entrySet; |
2012 |
} |
2013 |
} |
2014 |
|
2015 |
public Collection<V> values() { |
2016 |
synchronized(mutex) { |
2017 |
if (values==null) |
2018 |
values = new SynchronizedCollection<V>(m.values(), mutex); |
2019 |
return values; |
2020 |
} |
2021 |
} |
2022 |
|
2023 |
public boolean equals(Object o) { |
2024 |
synchronized(mutex) {return m.equals(o);} |
2025 |
} |
2026 |
public int hashCode() { |
2027 |
synchronized(mutex) {return m.hashCode();} |
2028 |
} |
2029 |
public String toString() { |
2030 |
synchronized(mutex) {return m.toString();} |
2031 |
} |
2032 |
private void writeObject(ObjectOutputStream s) throws IOException { |
2033 |
synchronized(mutex) {s.defaultWriteObject();} |
2034 |
} |
2035 |
} |
2036 |
|
2037 |
/** |
2038 |
* Returns a synchronized (thread-safe) sorted map backed by the specified |
2039 |
* sorted map. In order to guarantee serial access, it is critical that |
2040 |
* <strong>all</strong> access to the backing sorted map is accomplished |
2041 |
* through the returned sorted map (or its views).<p> |
2042 |
* |
2043 |
* It is imperative that the user manually synchronize on the returned |
2044 |
* sorted map when iterating over any of its collection views, or the |
2045 |
* collections views of any of its <tt>subMap</tt>, <tt>headMap</tt> or |
2046 |
* <tt>tailMap</tt> views. |
2047 |
* <pre> |
2048 |
* SortedMap m = Collections.synchronizedSortedMap(new TreeMap()); |
2049 |
* ... |
2050 |
* Set s = m.keySet(); // Needn't be in synchronized block |
2051 |
* ... |
2052 |
* synchronized(m) { // Synchronizing on m, not s! |
2053 |
* Iterator i = s.iterator(); // Must be in synchronized block |
2054 |
* while (i.hasNext()) |
2055 |
* foo(i.next()); |
2056 |
* } |
2057 |
* </pre> |
2058 |
* or: |
2059 |
* <pre> |
2060 |
* SortedMap m = Collections.synchronizedSortedMap(new TreeMap()); |
2061 |
* SortedMap m2 = m.subMap(foo, bar); |
2062 |
* ... |
2063 |
* Set s2 = m2.keySet(); // Needn't be in synchronized block |
2064 |
* ... |
2065 |
* synchronized(m) { // Synchronizing on m, not m2 or s2! |
2066 |
* Iterator i = s.iterator(); // Must be in synchronized block |
2067 |
* while (i.hasNext()) |
2068 |
* foo(i.next()); |
2069 |
* } |
2070 |
* </pre> |
2071 |
* Failure to follow this advice may result in non-deterministic behavior. |
2072 |
* |
2073 |
* <p>The returned sorted map will be serializable if the specified |
2074 |
* sorted map is serializable. |
2075 |
* |
2076 |
* @param m the sorted map to be "wrapped" in a synchronized sorted map. |
2077 |
* @return a synchronized view of the specified sorted map. |
2078 |
*/ |
2079 |
public static <K,V> SortedMap<K,V> synchronizedSortedMap(SortedMap<K,V> m) { |
2080 |
return new SynchronizedSortedMap<K,V>(m); |
2081 |
} |
2082 |
|
2083 |
|
2084 |
/** |
2085 |
* @serial include |
2086 |
*/ |
2087 |
static class SynchronizedSortedMap<K,V> |
2088 |
extends SynchronizedMap<K,V> |
2089 |
implements SortedMap<K,V> |
2090 |
{ |
2091 |
private static final long serialVersionUID = -8798146769416483793L; |
2092 |
|
2093 |
private final SortedMap<K,V> sm; |
2094 |
|
2095 |
SynchronizedSortedMap(SortedMap<K,V> m) { |
2096 |
super(m); |
2097 |
sm = m; |
2098 |
} |
2099 |
SynchronizedSortedMap(SortedMap<K,V> m, Object mutex) { |
2100 |
super(m, mutex); |
2101 |
sm = m; |
2102 |
} |
2103 |
|
2104 |
public Comparator<? super K> comparator() { |
2105 |
synchronized(mutex) {return sm.comparator();} |
2106 |
} |
2107 |
|
2108 |
public SortedMap<K,V> subMap(K fromKey, K toKey) { |
2109 |
synchronized(mutex) { |
2110 |
return new SynchronizedSortedMap<K,V>( |
2111 |
sm.subMap(fromKey, toKey), mutex); |
2112 |
} |
2113 |
} |
2114 |
public SortedMap<K,V> headMap(K toKey) { |
2115 |
synchronized(mutex) { |
2116 |
return new SynchronizedSortedMap<K,V>(sm.headMap(toKey), mutex); |
2117 |
} |
2118 |
} |
2119 |
public SortedMap<K,V> tailMap(K fromKey) { |
2120 |
synchronized(mutex) { |
2121 |
return new SynchronizedSortedMap<K,V>(sm.tailMap(fromKey),mutex); |
2122 |
} |
2123 |
} |
2124 |
|
2125 |
public K firstKey() { |
2126 |
synchronized(mutex) {return sm.firstKey();} |
2127 |
} |
2128 |
public K lastKey() { |
2129 |
synchronized(mutex) {return sm.lastKey();} |
2130 |
} |
2131 |
} |
2132 |
|
2133 |
// Dynamically typesafe collection wrappers |
2134 |
|
2135 |
/** |
2136 |
* Returns a dynamically typesafe view of the specified collection. Any |
2137 |
* attempt to insert an element of the wrong type will result in an |
2138 |
* immediate <tt>ClassCastException</tt>. Assuming a collection contains |
2139 |
* no incorrectly typed elements prior to the time a dynamically typesafe |
2140 |
* view is generated, and that all subsequent access to the collection |
2141 |
* takes place through the view, it is <i>guaranteed</i> that the |
2142 |
* collection cannot contain an incorrectly typed element. |
2143 |
* |
2144 |
* <p>The generics mechanism in the language provides compile-time |
2145 |
* (static) type checking, but it is possible to defeat this mechanism |
2146 |
* with unchecked casts. Usually this is not a problem, as the compiler |
2147 |
* issues warnings on all such unchecked operations. There are, however, |
2148 |
* times when static type checking alone is not sufficient. For example, |
2149 |
* suppose a collection is passed to a third-party library and it is |
2150 |
* imperative that the library code not corrupt the collection by |
2151 |
* inserting an element of the wrong type. |
2152 |
* |
2153 |
* <p>Another use of dynamically typesafe views is debugging. Suppose a |
2154 |
* program fails with a <tt>ClassCastException</tt>, indicating that an |
2155 |
* incorrectly typed element was put into a parameterized collection. |
2156 |
* Unfortunately, the exception can occur at any time after the erroneous |
2157 |
* element is inserted, so it typically provides little or no information |
2158 |
* as to the real source of the problem. If the problem is reproducible, |
2159 |
* one can quickly determine its source by temporarily modifying the |
2160 |
* program to wrap the collection with a dynamically typesafe view. |
2161 |
* For example, this declaration: |
2162 |
* <pre> |
2163 |
* Collection<String> c = new HashSet<String>(); |
2164 |
* </pre> |
2165 |
* may be replaced temporarily by this one: |
2166 |
* <pre> |
2167 |
* Collection<String> c = Collections.checkedCollection( |
2168 |
* new HashSet<String>(), String.class); |
2169 |
* </pre> |
2170 |
* Running the program again will cause it to fail at the point where |
2171 |
* an incorrectly typed element is inserted into the collection, clearly |
2172 |
* identifying the source of the problem. Once the problem is fixed, the |
2173 |
* modified declaration may be reverted back to the original. |
2174 |
* |
2175 |
* <p>The returned collection does <i>not</i> pass the hashCode and equals |
2176 |
* operations through to the backing collection, but relies on |
2177 |
* <tt>Object</tt>'s <tt>equals</tt> and <tt>hashCode</tt> methods. This |
2178 |
* is necessary to preserve the contracts of these operations in the case |
2179 |
* that the backing collection is a set or a list. |
2180 |
* |
2181 |
* <p>The returned collection will be serializable if the specified |
2182 |
* collection is serializable. |
2183 |
* |
2184 |
* @param c the collection for which a dynamically typesafe view is to be |
2185 |
* returned |
2186 |
* @param type the type of element that <tt>c</tt> is permitted to hold |
2187 |
* @return a dynamically typesafe view of the specified collection |
2188 |
* @since 1.5 |
2189 |
*/ |
2190 |
public static <E> Collection<E> checkedCollection(Collection<E> c, |
2191 |
Class<E> type) { |
2192 |
return new CheckedCollection<E>(c, type); |
2193 |
} |
2194 |
|
2195 |
/** |
2196 |
* @serial include |
2197 |
*/ |
2198 |
static class CheckedCollection<E> implements Collection<E>, Serializable { |
2199 |
private static final long serialVersionUID = 1578914078182001775L; |
2200 |
|
2201 |
final Collection<E> c; |
2202 |
final Class<E> type; |
2203 |
|
2204 |
void typeCheck(Object o) { |
2205 |
if (!type.isInstance(o)) |
2206 |
throw new ClassCastException("Attempt to insert " + |
2207 |
o.getClass() + " element into collection with element type " |
2208 |
+ type); |
2209 |
} |
2210 |
|
2211 |
CheckedCollection(Collection<E> c, Class<E> type) { |
2212 |
if (c==null || type == null) |
2213 |
throw new NullPointerException(); |
2214 |
this.c = c; |
2215 |
this.type = type; |
2216 |
} |
2217 |
|
2218 |
public int size() { return c.size(); } |
2219 |
public boolean isEmpty() { return c.isEmpty(); } |
2220 |
public boolean contains(Object o) { return c.contains(o); } |
2221 |
public Object[] toArray() { return c.toArray(); } |
2222 |
public <T> T[] toArray(T[] a) { return c.toArray(a); } |
2223 |
public String toString() { return c.toString(); } |
2224 |
public Iterator<E> iterator() { return c.iterator(); } |
2225 |
public boolean remove(Object o) { return c.remove(o); } |
2226 |
public boolean containsAll(Collection<?> coll) { |
2227 |
return c.containsAll(coll); |
2228 |
} |
2229 |
public boolean removeAll(Collection<?> coll) { |
2230 |
return c.removeAll(coll); |
2231 |
} |
2232 |
public boolean retainAll(Collection<?> coll) { |
2233 |
return c.retainAll(coll); |
2234 |
} |
2235 |
public void clear() { |
2236 |
c.clear(); |
2237 |
} |
2238 |
|
2239 |
public boolean add(E e){ |
2240 |
typeCheck(e); |
2241 |
return c.add(e); |
2242 |
} |
2243 |
|
2244 |
public boolean addAll(Collection<? extends E> coll) { |
2245 |
/* |
2246 |
* Dump coll into an array of the required type. This serves |
2247 |
* three purposes: it insulates us from concurrent changes in |
2248 |
* the contents of coll, it type-checks all of the elements in |
2249 |
* coll, and it provides all-or-nothing semantics (which we |
2250 |
* wouldn't get if we type-checked each element as we added it). |
2251 |
*/ |
2252 |
E[] a = null; |
2253 |
try { |
2254 |
a = coll.toArray(zeroLengthElementArray()); |
2255 |
} catch (ArrayStoreException e) { |
2256 |
throw new ClassCastException(); |
2257 |
} |
2258 |
|
2259 |
boolean result = false; |
2260 |
for (E e : a) |
2261 |
result |= c.add(e); |
2262 |
return result; |
2263 |
} |
2264 |
|
2265 |
private E[] zeroLengthElementArray = null; // Lazily initialized |
2266 |
|
2267 |
/* |
2268 |
* We don't need locking or volatile, because it's OK if we create |
2269 |
* several zeroLengthElementArrays, and they're immutable. |
2270 |
*/ |
2271 |
E[] zeroLengthElementArray() { |
2272 |
if (zeroLengthElementArray == null) |
2273 |
zeroLengthElementArray = (E[]) Array.newInstance(type, 0); |
2274 |
return zeroLengthElementArray; |
2275 |
} |
2276 |
} |
2277 |
|
2278 |
/** |
2279 |
* Returns a dynamically typesafe view of the specified set. |
2280 |
* Any attempt to insert an element of the wrong type will result in |
2281 |
* an immediate <tt>ClassCastException</tt>. Assuming a set contains |
2282 |
* no incorrectly typed elements prior to the time a dynamically typesafe |
2283 |
* view is generated, and that all subsequent access to the set |
2284 |
* takes place through the view, it is <i>guaranteed</i> that the |
2285 |
* set cannot contain an incorrectly typed element. |
2286 |
* |
2287 |
* <p>A discussion of the use of dynamically typesafe views may be |
2288 |
* found in the documentation for the {@link #checkedCollection checkedCollection} |
2289 |
* method. |
2290 |
* |
2291 |
* <p>The returned set will be serializable if the specified set is |
2292 |
* serializable. |
2293 |
* |
2294 |
* @param s the set for which a dynamically typesafe view is to be |
2295 |
* returned |
2296 |
* @param type the type of element that <tt>s</tt> is permitted to hold |
2297 |
* @return a dynamically typesafe view of the specified set |
2298 |
* @since 1.5 |
2299 |
*/ |
2300 |
public static <E> Set<E> checkedSet(Set<E> s, Class<E> type) { |
2301 |
return new CheckedSet<E>(s, type); |
2302 |
} |
2303 |
|
2304 |
/** |
2305 |
* @serial include |
2306 |
*/ |
2307 |
static class CheckedSet<E> extends CheckedCollection<E> |
2308 |
implements Set<E>, Serializable |
2309 |
{ |
2310 |
private static final long serialVersionUID = 4694047833775013803L; |
2311 |
|
2312 |
CheckedSet(Set<E> s, Class<E> elementType) { super(s, elementType); } |
2313 |
|
2314 |
public boolean equals(Object o) { return c.equals(o); } |
2315 |
public int hashCode() { return c.hashCode(); } |
2316 |
} |
2317 |
|
2318 |
/** |
2319 |
* Returns a dynamically typesafe view of the specified sorted set. Any |
2320 |
* attempt to insert an element of the wrong type will result in an |
2321 |
* immediate <tt>ClassCastException</tt>. Assuming a sorted set contains |
2322 |
* no incorrectly typed elements prior to the time a dynamically typesafe |
2323 |
* view is generated, and that all subsequent access to the sorted set |
2324 |
* takes place through the view, it is <i>guaranteed</i> that the sorted |
2325 |
* set cannot contain an incorrectly typed element. |
2326 |
* |
2327 |
* <p>A discussion of the use of dynamically typesafe views may be |
2328 |
* found in the documentation for the {@link #checkedCollection checkedCollection} |
2329 |
* method. |
2330 |
* |
2331 |
* <p>The returned sorted set will be serializable if the specified sorted |
2332 |
* set is serializable. |
2333 |
* |
2334 |
* @param s the sorted set for which a dynamically typesafe view is to be |
2335 |
* returned |
2336 |
* @param type the type of element that <tt>s</tt> is permitted to hold |
2337 |
* @return a dynamically typesafe view of the specified sorted set |
2338 |
* @since 1.5 |
2339 |
*/ |
2340 |
public static <E> SortedSet<E> checkedSortedSet(SortedSet<E> s, |
2341 |
Class<E> type) { |
2342 |
return new CheckedSortedSet<E>(s, type); |
2343 |
} |
2344 |
|
2345 |
/** |
2346 |
* @serial include |
2347 |
*/ |
2348 |
static class CheckedSortedSet<E> extends CheckedSet<E> |
2349 |
implements SortedSet<E>, Serializable |
2350 |
{ |
2351 |
private static final long serialVersionUID = 1599911165492914959L; |
2352 |
private final SortedSet<E> ss; |
2353 |
|
2354 |
CheckedSortedSet(SortedSet<E> s, Class<E> type) { |
2355 |
super(s, type); |
2356 |
ss = s; |
2357 |
} |
2358 |
|
2359 |
public Comparator<? super E> comparator() { return ss.comparator(); } |
2360 |
public E first() { return ss.first(); } |
2361 |
public E last() { return ss.last(); } |
2362 |
|
2363 |
public SortedSet<E> subSet(E fromElement, E toElement) { |
2364 |
return new CheckedSortedSet<E>(ss.subSet(fromElement,toElement), |
2365 |
type); |
2366 |
} |
2367 |
public SortedSet<E> headSet(E toElement) { |
2368 |
return new CheckedSortedSet<E>(ss.headSet(toElement), type); |
2369 |
} |
2370 |
public SortedSet<E> tailSet(E fromElement) { |
2371 |
return new CheckedSortedSet<E>(ss.tailSet(fromElement), type); |
2372 |
} |
2373 |
} |
2374 |
|
2375 |
/** |
2376 |
* Returns a dynamically typesafe view of the specified list. |
2377 |
* Any attempt to insert an element of the wrong type will result in |
2378 |
* an immediate <tt>ClassCastException</tt>. Assuming a list contains |
2379 |
* no incorrectly typed elements prior to the time a dynamically typesafe |
2380 |
* view is generated, and that all subsequent access to the list |
2381 |
* takes place through the view, it is <i>guaranteed</i> that the |
2382 |
* list cannot contain an incorrectly typed element. |
2383 |
* |
2384 |
* <p>A discussion of the use of dynamically typesafe views may be |
2385 |
* found in the documentation for the {@link #checkedCollection checkedCollection} |
2386 |
* method. |
2387 |
* |
2388 |
* <p>The returned list will be serializable if the specified list is |
2389 |
* serializable. |
2390 |
* |
2391 |
* @param list the list for which a dynamically typesafe view is to be |
2392 |
* returned |
2393 |
* @param type the type of element that <tt>list</tt> is permitted to hold |
2394 |
* @return a dynamically typesafe view of the specified list |
2395 |
* @since 1.5 |
2396 |
*/ |
2397 |
public static <E> List<E> checkedList(List<E> list, Class<E> type) { |
2398 |
return (list instanceof RandomAccess ? |
2399 |
new CheckedRandomAccessList<E>(list, type) : |
2400 |
new CheckedList<E>(list, type)); |
2401 |
} |
2402 |
|
2403 |
/** |
2404 |
* @serial include |
2405 |
*/ |
2406 |
static class CheckedList<E> extends CheckedCollection<E> |
2407 |
implements List<E> |
2408 |
{ |
2409 |
static final long serialVersionUID = 65247728283967356L; |
2410 |
final List<E> list; |
2411 |
|
2412 |
CheckedList(List<E> list, Class<E> type) { |
2413 |
super(list, type); |
2414 |
this.list = list; |
2415 |
} |
2416 |
|
2417 |
public boolean equals(Object o) { return list.equals(o); } |
2418 |
public int hashCode() { return list.hashCode(); } |
2419 |
public E get(int index) { return list.get(index); } |
2420 |
public E remove(int index) { return list.remove(index); } |
2421 |
public int indexOf(Object o) { return list.indexOf(o); } |
2422 |
public int lastIndexOf(Object o) { return list.lastIndexOf(o); } |
2423 |
|
2424 |
public E set(int index, E element) { |
2425 |
typeCheck(element); |
2426 |
return list.set(index, element); |
2427 |
} |
2428 |
|
2429 |
public void add(int index, E element) { |
2430 |
typeCheck(element); |
2431 |
list.add(index, element); |
2432 |
} |
2433 |
|
2434 |
public boolean addAll(int index, Collection<? extends E> c) { |
2435 |
// See CheckCollection.addAll, above, for an explanation |
2436 |
E[] a = null; |
2437 |
try { |
2438 |
a = c.toArray(zeroLengthElementArray()); |
2439 |
} catch (ArrayStoreException e) { |
2440 |
throw new ClassCastException(); |
2441 |
} |
2442 |
|
2443 |
return list.addAll(index, Arrays.asList(a)); |
2444 |
} |
2445 |
public ListIterator<E> listIterator() { return listIterator(0); } |
2446 |
|
2447 |
public ListIterator<E> listIterator(final int index) { |
2448 |
return new ListIterator<E>() { |
2449 |
ListIterator<E> i = list.listIterator(index); |
2450 |
|
2451 |
public boolean hasNext() { return i.hasNext(); } |
2452 |
public E next() { return i.next(); } |
2453 |
public boolean hasPrevious() { return i.hasPrevious(); } |
2454 |
public E previous() { return i.previous(); } |
2455 |
public int nextIndex() { return i.nextIndex(); } |
2456 |
public int previousIndex() { return i.previousIndex(); } |
2457 |
public void remove() { i.remove(); } |
2458 |
|
2459 |
public void set(E e) { |
2460 |
typeCheck(e); |
2461 |
i.set(e); |
2462 |
} |
2463 |
|
2464 |
public void add(E e) { |
2465 |
typeCheck(e); |
2466 |
i.add(e); |
2467 |
} |
2468 |
}; |
2469 |
} |
2470 |
|
2471 |
public List<E> subList(int fromIndex, int toIndex) { |
2472 |
return new CheckedList<E>(list.subList(fromIndex, toIndex), type); |
2473 |
} |
2474 |
} |
2475 |
|
2476 |
/** |
2477 |
* @serial include |
2478 |
*/ |
2479 |
static class CheckedRandomAccessList<E> extends CheckedList<E> |
2480 |
implements RandomAccess |
2481 |
{ |
2482 |
private static final long serialVersionUID = 1638200125423088369L; |
2483 |
|
2484 |
CheckedRandomAccessList(List<E> list, Class<E> type) { |
2485 |
super(list, type); |
2486 |
} |
2487 |
|
2488 |
public List<E> subList(int fromIndex, int toIndex) { |
2489 |
return new CheckedRandomAccessList<E>( |
2490 |
list.subList(fromIndex, toIndex), type); |
2491 |
} |
2492 |
} |
2493 |
|
2494 |
/** |
2495 |
* Returns a dynamically typesafe view of the specified map. Any attempt |
2496 |
* to insert a mapping whose key or value have the wrong type will result |
2497 |
* in an immediate <tt>ClassCastException</tt>. Similarly, any attempt to |
2498 |
* modify the value currently associated with a key will result in an |
2499 |
* immediate <tt>ClassCastException</tt>, whether the modification is |
2500 |
* attempted directly through the map itself, or through a {@link |
2501 |
* Map.Entry} instance obtained from the map's {@link Map#entrySet() |
2502 |
* entry set} view. |
2503 |
* |
2504 |
* <p>Assuming a map contains no incorrectly typed keys or values |
2505 |
* prior to the time a dynamically typesafe view is generated, and |
2506 |
* that all subsequent access to the map takes place through the view |
2507 |
* (or one of its collection views), it is <i>guaranteed</i> that the |
2508 |
* map cannot contain an incorrectly typed key or value. |
2509 |
* |
2510 |
* <p>A discussion of the use of dynamically typesafe views may be |
2511 |
* found in the documentation for the {@link #checkedCollection checkedCollection} |
2512 |
* method. |
2513 |
* |
2514 |
* <p>The returned map will be serializable if the specified map is |
2515 |
* serializable. |
2516 |
* |
2517 |
* @param m the map for which a dynamically typesafe view is to be |
2518 |
* returned |
2519 |
* @param keyType the type of key that <tt>m</tt> is permitted to hold |
2520 |
* @param valueType the type of value that <tt>m</tt> is permitted to hold |
2521 |
* @return a dynamically typesafe view of the specified map |
2522 |
* @since 1.5 |
2523 |
*/ |
2524 |
public static <K, V> Map<K, V> checkedMap(Map<K, V> m, Class<K> keyType, |
2525 |
Class<V> valueType) { |
2526 |
return new CheckedMap<K,V>(m, keyType, valueType); |
2527 |
} |
2528 |
|
2529 |
|
2530 |
/** |
2531 |
* @serial include |
2532 |
*/ |
2533 |
private static class CheckedMap<K,V> implements Map<K,V>, |
2534 |
Serializable |
2535 |
{ |
2536 |
private static final long serialVersionUID = 5742860141034234728L; |
2537 |
|
2538 |
private final Map<K, V> m; |
2539 |
final Class<K> keyType; |
2540 |
final Class<V> valueType; |
2541 |
|
2542 |
private void typeCheck(Object key, Object value) { |
2543 |
if (!keyType.isInstance(key)) |
2544 |
throw new ClassCastException("Attempt to insert " + |
2545 |
key.getClass() + " key into collection with key type " |
2546 |
+ keyType); |
2547 |
|
2548 |
if (!valueType.isInstance(value)) |
2549 |
throw new ClassCastException("Attempt to insert " + |
2550 |
value.getClass() +" value into collection with value type " |
2551 |
+ valueType); |
2552 |
} |
2553 |
|
2554 |
CheckedMap(Map<K, V> m, Class<K> keyType, Class<V> valueType) { |
2555 |
if (m == null || keyType == null || valueType == null) |
2556 |
throw new NullPointerException(); |
2557 |
this.m = m; |
2558 |
this.keyType = keyType; |
2559 |
this.valueType = valueType; |
2560 |
} |
2561 |
|
2562 |
public int size() { return m.size(); } |
2563 |
public boolean isEmpty() { return m.isEmpty(); } |
2564 |
public boolean containsKey(Object key) { return m.containsKey(key); } |
2565 |
public boolean containsValue(Object v) { return m.containsValue(v); } |
2566 |
public V get(Object key) { return m.get(key); } |
2567 |
public V remove(Object key) { return m.remove(key); } |
2568 |
public void clear() { m.clear(); } |
2569 |
public Set<K> keySet() { return m.keySet(); } |
2570 |
public Collection<V> values() { return m.values(); } |
2571 |
public boolean equals(Object o) { return m.equals(o); } |
2572 |
public int hashCode() { return m.hashCode(); } |
2573 |
public String toString() { return m.toString(); } |
2574 |
|
2575 |
public V put(K key, V value) { |
2576 |
typeCheck(key, value); |
2577 |
return m.put(key, value); |
2578 |
} |
2579 |
|
2580 |
public void putAll(Map<? extends K, ? extends V> t) { |
2581 |
// See CheckCollection.addAll, above, for an explanation |
2582 |
K[] keys = null; |
2583 |
try { |
2584 |
keys = t.keySet().toArray(zeroLengthKeyArray()); |
2585 |
} catch (ArrayStoreException e) { |
2586 |
throw new ClassCastException(); |
2587 |
} |
2588 |
V[] values = null; |
2589 |
try { |
2590 |
values = t.values().toArray(zeroLengthValueArray()); |
2591 |
} catch (ArrayStoreException e) { |
2592 |
throw new ClassCastException(); |
2593 |
} |
2594 |
|
2595 |
if (keys.length != values.length) |
2596 |
throw new ConcurrentModificationException(); |
2597 |
|
2598 |
for (int i = 0; i < keys.length; i++) |
2599 |
m.put(keys[i], values[i]); |
2600 |
} |
2601 |
|
2602 |
// Lazily initialized |
2603 |
private K[] zeroLengthKeyArray = null; |
2604 |
private V[] zeroLengthValueArray = null; |
2605 |
|
2606 |
/* |
2607 |
* We don't need locking or volatile, because it's OK if we create |
2608 |
* several zeroLengthValueArrays, and they're immutable. |
2609 |
*/ |
2610 |
private K[] zeroLengthKeyArray() { |
2611 |
if (zeroLengthKeyArray == null) |
2612 |
zeroLengthKeyArray = (K[]) Array.newInstance(keyType, 0); |
2613 |
return zeroLengthKeyArray; |
2614 |
} |
2615 |
private V[] zeroLengthValueArray() { |
2616 |
if (zeroLengthValueArray == null) |
2617 |
zeroLengthValueArray = (V[]) Array.newInstance(valueType, 0); |
2618 |
return zeroLengthValueArray; |
2619 |
} |
2620 |
|
2621 |
private transient Set<Map.Entry<K,V>> entrySet = null; |
2622 |
|
2623 |
public Set<Map.Entry<K,V>> entrySet() { |
2624 |
if (entrySet==null) |
2625 |
entrySet = new CheckedEntrySet<K,V>(m.entrySet(), valueType); |
2626 |
return entrySet; |
2627 |
} |
2628 |
|
2629 |
/** |
2630 |
* We need this class in addition to CheckedSet as Map.Entry permits |
2631 |
* modification of the backing Map via the setValue operation. This |
2632 |
* class is subtle: there are many possible attacks that must be |
2633 |
* thwarted. |
2634 |
* |
2635 |
* @serial exclude |
2636 |
*/ |
2637 |
static class CheckedEntrySet<K,V> implements Set<Map.Entry<K,V>> { |
2638 |
Set<Map.Entry<K,V>> s; |
2639 |
Class<V> valueType; |
2640 |
|
2641 |
CheckedEntrySet(Set<Map.Entry<K, V>> s, Class<V> valueType) { |
2642 |
this.s = s; |
2643 |
this.valueType = valueType; |
2644 |
} |
2645 |
|
2646 |
public int size() { return s.size(); } |
2647 |
public boolean isEmpty() { return s.isEmpty(); } |
2648 |
public String toString() { return s.toString(); } |
2649 |
public int hashCode() { return s.hashCode(); } |
2650 |
public boolean remove(Object o) { return s.remove(o); } |
2651 |
public boolean removeAll(Collection<?> coll) { |
2652 |
return s.removeAll(coll); |
2653 |
} |
2654 |
public boolean retainAll(Collection<?> coll) { |
2655 |
return s.retainAll(coll); |
2656 |
} |
2657 |
public void clear() { |
2658 |
s.clear(); |
2659 |
} |
2660 |
|
2661 |
public boolean add(Map.Entry<K, V> e){ |
2662 |
throw new UnsupportedOperationException(); |
2663 |
} |
2664 |
public boolean addAll(Collection<? extends Map.Entry<K, V>> coll) { |
2665 |
throw new UnsupportedOperationException(); |
2666 |
} |
2667 |
|
2668 |
|
2669 |
public Iterator<Map.Entry<K,V>> iterator() { |
2670 |
return new Iterator<Map.Entry<K,V>>() { |
2671 |
Iterator<Map.Entry<K, V>> i = s.iterator(); |
2672 |
|
2673 |
public boolean hasNext() { return i.hasNext(); } |
2674 |
public void remove() { i.remove(); } |
2675 |
|
2676 |
public Map.Entry<K,V> next() { |
2677 |
return new CheckedEntry<K,V>(i.next(), valueType); |
2678 |
} |
2679 |
}; |
2680 |
} |
2681 |
|
2682 |
public Object[] toArray() { |
2683 |
Object[] source = s.toArray(); |
2684 |
|
2685 |
/* |
2686 |
* Ensure that we don't get an ArrayStoreException even if |
2687 |
* s.toArray returns an array of something other than Object |
2688 |
*/ |
2689 |
Object[] dest = (CheckedEntry.class.isInstance( |
2690 |
source.getClass().getComponentType()) ? source : |
2691 |
new Object[source.length]); |
2692 |
|
2693 |
for (int i = 0; i < source.length; i++) |
2694 |
dest[i] = new CheckedEntry<K,V>((Map.Entry<K,V>)source[i], |
2695 |
valueType); |
2696 |
return dest; |
2697 |
} |
2698 |
|
2699 |
public <T> T[] toArray(T[] a) { |
2700 |
// We don't pass a to s.toArray, to avoid window of |
2701 |
// vulnerability wherein an unscrupulous multithreaded client |
2702 |
// could get his hands on raw (unwrapped) Entries from s. |
2703 |
Object[] arr = s.toArray(a.length==0 ? a : Arrays.copyOf(a, 0)); |
2704 |
|
2705 |
for (int i=0; i<arr.length; i++) |
2706 |
arr[i] = new CheckedEntry<K,V>((Map.Entry<K,V>)arr[i], |
2707 |
valueType); |
2708 |
if (arr.length > a.length) |
2709 |
return (T[])arr; |
2710 |
|
2711 |
System.arraycopy(arr, 0, a, 0, arr.length); |
2712 |
if (a.length > arr.length) |
2713 |
a[arr.length] = null; |
2714 |
return a; |
2715 |
} |
2716 |
|
2717 |
/** |
2718 |
* This method is overridden to protect the backing set against |
2719 |
* an object with a nefarious equals function that senses |
2720 |
* that the equality-candidate is Map.Entry and calls its |
2721 |
* setValue method. |
2722 |
*/ |
2723 |
public boolean contains(Object o) { |
2724 |
if (!(o instanceof Map.Entry)) |
2725 |
return false; |
2726 |
return s.contains( |
2727 |
new CheckedEntry<K,V>((Map.Entry<K,V>) o, valueType)); |
2728 |
} |
2729 |
|
2730 |
/** |
2731 |
* The next two methods are overridden to protect against |
2732 |
* an unscrupulous collection whose contains(Object o) method |
2733 |
* senses when o is a Map.Entry, and calls o.setValue. |
2734 |
*/ |
2735 |
public boolean containsAll(Collection<?> coll) { |
2736 |
Iterator<?> e = coll.iterator(); |
2737 |
while (e.hasNext()) |
2738 |
if (!contains(e.next())) // Invokes safe contains() above |
2739 |
return false; |
2740 |
return true; |
2741 |
} |
2742 |
|
2743 |
public boolean equals(Object o) { |
2744 |
if (o == this) |
2745 |
return true; |
2746 |
if (!(o instanceof Set)) |
2747 |
return false; |
2748 |
Set<?> that = (Set<?>) o; |
2749 |
if (that.size() != s.size()) |
2750 |
return false; |
2751 |
return containsAll(that); // Invokes safe containsAll() above |
2752 |
} |
2753 |
|
2754 |
/** |
2755 |
* This "wrapper class" serves two purposes: it prevents |
2756 |
* the client from modifying the backing Map, by short-circuiting |
2757 |
* the setValue method, and it protects the backing Map against |
2758 |
* an ill-behaved Map.Entry that attempts to modify another |
2759 |
* Map Entry when asked to perform an equality check. |
2760 |
*/ |
2761 |
private static class CheckedEntry<K,V> implements Map.Entry<K,V> { |
2762 |
private Map.Entry<K, V> e; |
2763 |
private Class<V> valueType; |
2764 |
|
2765 |
CheckedEntry(Map.Entry<K, V> e, Class<V> valueType) { |
2766 |
this.e = e; |
2767 |
this.valueType = valueType; |
2768 |
} |
2769 |
|
2770 |
public K getKey() { return e.getKey(); } |
2771 |
public V getValue() { return e.getValue(); } |
2772 |
public int hashCode() { return e.hashCode(); } |
2773 |
public String toString() { return e.toString(); } |
2774 |
|
2775 |
|
2776 |
public V setValue(V value) { |
2777 |
if (!valueType.isInstance(value)) |
2778 |
throw new ClassCastException("Attempt to insert " + |
2779 |
value.getClass() + |
2780 |
" value into collection with value type " + valueType); |
2781 |
return e.setValue(value); |
2782 |
} |
2783 |
|
2784 |
public boolean equals(Object o) { |
2785 |
if (!(o instanceof Map.Entry)) |
2786 |
return false; |
2787 |
Map.Entry t = (Map.Entry)o; |
2788 |
return eq(e.getKey(), t.getKey()) && |
2789 |
eq(e.getValue(), t.getValue()); |
2790 |
} |
2791 |
} |
2792 |
} |
2793 |
} |
2794 |
|
2795 |
/** |
2796 |
* Returns a dynamically typesafe view of the specified sorted map. Any |
2797 |
* attempt to insert a mapping whose key or value have the wrong type will |
2798 |
* result in an immediate <tt>ClassCastException</tt>. Similarly, any |
2799 |
* attempt to modify the value currently associated with a key will result |
2800 |
* in an immediate <tt>ClassCastException</tt>, whether the modification |
2801 |
* is attempted directly through the map itself, or through a {@link |
2802 |
* Map.Entry} instance obtained from the map's {@link Map#entrySet() entry |
2803 |
* set} view. |
2804 |
* |
2805 |
* <p>Assuming a map contains no incorrectly typed keys or values |
2806 |
* prior to the time a dynamically typesafe view is generated, and |
2807 |
* that all subsequent access to the map takes place through the view |
2808 |
* (or one of its collection views), it is <i>guaranteed</i> that the |
2809 |
* map cannot contain an incorrectly typed key or value. |
2810 |
* |
2811 |
* <p>A discussion of the use of dynamically typesafe views may be |
2812 |
* found in the documentation for the {@link #checkedCollection checkedCollection} |
2813 |
* method. |
2814 |
* |
2815 |
* <p>The returned map will be serializable if the specified map is |
2816 |
* serializable. |
2817 |
* |
2818 |
* @param m the map for which a dynamically typesafe view is to be |
2819 |
* returned |
2820 |
* @param keyType the type of key that <tt>m</tt> is permitted to hold |
2821 |
* @param valueType the type of value that <tt>m</tt> is permitted to hold |
2822 |
* @return a dynamically typesafe view of the specified map |
2823 |
* @since 1.5 |
2824 |
*/ |
2825 |
public static <K,V> SortedMap<K,V> checkedSortedMap(SortedMap<K, V> m, |
2826 |
Class<K> keyType, |
2827 |
Class<V> valueType) { |
2828 |
return new CheckedSortedMap<K,V>(m, keyType, valueType); |
2829 |
} |
2830 |
|
2831 |
/** |
2832 |
* @serial include |
2833 |
*/ |
2834 |
static class CheckedSortedMap<K,V> extends CheckedMap<K,V> |
2835 |
implements SortedMap<K,V>, Serializable |
2836 |
{ |
2837 |
private static final long serialVersionUID = 1599671320688067438L; |
2838 |
|
2839 |
private final SortedMap<K, V> sm; |
2840 |
|
2841 |
CheckedSortedMap(SortedMap<K, V> m, |
2842 |
Class<K> keyType, Class<V> valueType) { |
2843 |
super(m, keyType, valueType); |
2844 |
sm = m; |
2845 |
} |
2846 |
|
2847 |
public Comparator<? super K> comparator() { return sm.comparator(); } |
2848 |
public K firstKey() { return sm.firstKey(); } |
2849 |
public K lastKey() { return sm.lastKey(); } |
2850 |
|
2851 |
public SortedMap<K,V> subMap(K fromKey, K toKey) { |
2852 |
return new CheckedSortedMap<K,V>(sm.subMap(fromKey, toKey), |
2853 |
keyType, valueType); |
2854 |
} |
2855 |
|
2856 |
public SortedMap<K,V> headMap(K toKey) { |
2857 |
return new CheckedSortedMap<K,V>(sm.headMap(toKey), |
2858 |
keyType, valueType); |
2859 |
} |
2860 |
|
2861 |
public SortedMap<K,V> tailMap(K fromKey) { |
2862 |
return new CheckedSortedMap<K,V>(sm.tailMap(fromKey), |
2863 |
keyType, valueType); |
2864 |
} |
2865 |
} |
2866 |
|
2867 |
// Miscellaneous |
2868 |
|
2869 |
/** |
2870 |
* The empty set (immutable). This set is serializable. |
2871 |
* |
2872 |
* @see #emptySet() |
2873 |
*/ |
2874 |
public static final Set EMPTY_SET = new EmptySet(); |
2875 |
|
2876 |
/** |
2877 |
* Returns the empty set (immutable). This set is serializable. |
2878 |
* Unlike the like-named field, this method is parameterized. |
2879 |
* |
2880 |
* <p>This example illustrates the type-safe way to obtain an empty set: |
2881 |
* <pre> |
2882 |
* Set<String> s = Collections.emptySet(); |
2883 |
* </pre> |
2884 |
* Implementation note: Implementations of this method need not |
2885 |
* create a separate <tt>Set</tt> object for each call. Using this |
2886 |
* method is likely to have comparable cost to using the like-named |
2887 |
* field. (Unlike this method, the field does not provide type safety.) |
2888 |
* |
2889 |
* @see #EMPTY_SET |
2890 |
* @since 1.5 |
2891 |
*/ |
2892 |
public static final <T> Set<T> emptySet() { |
2893 |
return (Set<T>) EMPTY_SET; |
2894 |
} |
2895 |
|
2896 |
/** |
2897 |
* @serial include |
2898 |
*/ |
2899 |
private static class EmptySet extends AbstractSet<Object> implements Serializable { |
2900 |
// use serialVersionUID from JDK 1.2.2 for interoperability |
2901 |
private static final long serialVersionUID = 1582296315990362920L; |
2902 |
|
2903 |
public Iterator<Object> iterator() { |
2904 |
return new Iterator<Object>() { |
2905 |
public boolean hasNext() { |
2906 |
return false; |
2907 |
} |
2908 |
public Object next() { |
2909 |
throw new NoSuchElementException(); |
2910 |
} |
2911 |
public void remove() { |
2912 |
throw new UnsupportedOperationException(); |
2913 |
} |
2914 |
}; |
2915 |
} |
2916 |
|
2917 |
public int size() {return 0;} |
2918 |
|
2919 |
public boolean contains(Object obj) {return false;} |
2920 |
|
2921 |
// Preserves singleton property |
2922 |
private Object readResolve() { |
2923 |
return EMPTY_SET; |
2924 |
} |
2925 |
} |
2926 |
|
2927 |
/** |
2928 |
* The empty list (immutable). This list is serializable. |
2929 |
* |
2930 |
* @see #emptyList() |
2931 |
*/ |
2932 |
public static final List EMPTY_LIST = new EmptyList(); |
2933 |
|
2934 |
/** |
2935 |
* Returns the empty list (immutable). This list is serializable. |
2936 |
* |
2937 |
* <p>This example illustrates the type-safe way to obtain an empty list: |
2938 |
* <pre> |
2939 |
* List<String> s = Collections.emptyList(); |
2940 |
* </pre> |
2941 |
* Implementation note: Implementations of this method need not |
2942 |
* create a separate <tt>List</tt> object for each call. Using this |
2943 |
* method is likely to have comparable cost to using the like-named |
2944 |
* field. (Unlike this method, the field does not provide type safety.) |
2945 |
* |
2946 |
* @see #EMPTY_LIST |
2947 |
* @since 1.5 |
2948 |
*/ |
2949 |
public static final <T> List<T> emptyList() { |
2950 |
return (List<T>) EMPTY_LIST; |
2951 |
} |
2952 |
|
2953 |
/** |
2954 |
* @serial include |
2955 |
*/ |
2956 |
private static class EmptyList |
2957 |
extends AbstractList<Object> |
2958 |
implements RandomAccess, Serializable { |
2959 |
// use serialVersionUID from JDK 1.2.2 for interoperability |
2960 |
private static final long serialVersionUID = 8842843931221139166L; |
2961 |
|
2962 |
public int size() {return 0;} |
2963 |
|
2964 |
public boolean contains(Object obj) {return false;} |
2965 |
|
2966 |
public Object get(int index) { |
2967 |
throw new IndexOutOfBoundsException("Index: "+index); |
2968 |
} |
2969 |
|
2970 |
// Preserves singleton property |
2971 |
private Object readResolve() { |
2972 |
return EMPTY_LIST; |
2973 |
} |
2974 |
} |
2975 |
|
2976 |
/** |
2977 |
* The empty map (immutable). This map is serializable. |
2978 |
* |
2979 |
* @see #emptyMap() |
2980 |
* @since 1.3 |
2981 |
*/ |
2982 |
public static final Map EMPTY_MAP = new EmptyMap(); |
2983 |
|
2984 |
/** |
2985 |
* Returns the empty map (immutable). This map is serializable. |
2986 |
* |
2987 |
* <p>This example illustrates the type-safe way to obtain an empty set: |
2988 |
* <pre> |
2989 |
* Map<String, Date> s = Collections.emptyMap(); |
2990 |
* </pre> |
2991 |
* Implementation note: Implementations of this method need not |
2992 |
* create a separate <tt>Map</tt> object for each call. Using this |
2993 |
* method is likely to have comparable cost to using the like-named |
2994 |
* field. (Unlike this method, the field does not provide type safety.) |
2995 |
* |
2996 |
* @see #EMPTY_MAP |
2997 |
* @since 1.5 |
2998 |
*/ |
2999 |
public static final <K,V> Map<K,V> emptyMap() { |
3000 |
return (Map<K,V>) EMPTY_MAP; |
3001 |
} |
3002 |
|
3003 |
private static class EmptyMap |
3004 |
extends AbstractMap<Object,Object> |
3005 |
implements Serializable { |
3006 |
|
3007 |
private static final long serialVersionUID = 6428348081105594320L; |
3008 |
|
3009 |
public int size() {return 0;} |
3010 |
|
3011 |
public boolean isEmpty() {return true;} |
3012 |
|
3013 |
public boolean containsKey(Object key) {return false;} |
3014 |
|
3015 |
public boolean containsValue(Object value) {return false;} |
3016 |
|
3017 |
public Object get(Object key) {return null;} |
3018 |
|
3019 |
public Set<Object> keySet() {return Collections.<Object>emptySet();} |
3020 |
|
3021 |
public Collection<Object> values() {return Collections.<Object>emptySet();} |
3022 |
|
3023 |
public Set<Map.Entry<Object,Object>> entrySet() { |
3024 |
return Collections.emptySet(); |
3025 |
} |
3026 |
|
3027 |
public boolean equals(Object o) { |
3028 |
return (o instanceof Map) && ((Map)o).size()==0; |
3029 |
} |
3030 |
|
3031 |
public int hashCode() {return 0;} |
3032 |
|
3033 |
// Preserves singleton property |
3034 |
private Object readResolve() { |
3035 |
return EMPTY_MAP; |
3036 |
} |
3037 |
} |
3038 |
|
3039 |
/** |
3040 |
* Returns an immutable set containing only the specified object. |
3041 |
* The returned set is serializable. |
3042 |
* |
3043 |
* @param o the sole object to be stored in the returned set. |
3044 |
* @return an immutable set containing only the specified object. |
3045 |
*/ |
3046 |
public static <T> Set<T> singleton(T o) { |
3047 |
return new SingletonSet<T>(o); |
3048 |
} |
3049 |
|
3050 |
/** |
3051 |
* @serial include |
3052 |
*/ |
3053 |
private static class SingletonSet<E> |
3054 |
extends AbstractSet<E> |
3055 |
implements Serializable |
3056 |
{ |
3057 |
// use serialVersionUID from JDK 1.2.2 for interoperability |
3058 |
private static final long serialVersionUID = 3193687207550431679L; |
3059 |
|
3060 |
final private E element; |
3061 |
|
3062 |
SingletonSet(E e) {element = e;} |
3063 |
|
3064 |
public Iterator<E> iterator() { |
3065 |
return new Iterator<E>() { |
3066 |
private boolean hasNext = true; |
3067 |
public boolean hasNext() { |
3068 |
return hasNext; |
3069 |
} |
3070 |
public E next() { |
3071 |
if (hasNext) { |
3072 |
hasNext = false; |
3073 |
return element; |
3074 |
} |
3075 |
throw new NoSuchElementException(); |
3076 |
} |
3077 |
public void remove() { |
3078 |
throw new UnsupportedOperationException(); |
3079 |
} |
3080 |
}; |
3081 |
} |
3082 |
|
3083 |
public int size() {return 1;} |
3084 |
|
3085 |
public boolean contains(Object o) {return eq(o, element);} |
3086 |
} |
3087 |
|
3088 |
/** |
3089 |
* Returns an immutable list containing only the specified object. |
3090 |
* The returned list is serializable. |
3091 |
* |
3092 |
* @param o the sole object to be stored in the returned list. |
3093 |
* @return an immutable list containing only the specified object. |
3094 |
* @since 1.3 |
3095 |
*/ |
3096 |
public static <T> List<T> singletonList(T o) { |
3097 |
return new SingletonList<T>(o); |
3098 |
} |
3099 |
|
3100 |
private static class SingletonList<E> |
3101 |
extends AbstractList<E> |
3102 |
implements RandomAccess, Serializable { |
3103 |
|
3104 |
static final long serialVersionUID = 3093736618740652951L; |
3105 |
|
3106 |
private final E element; |
3107 |
|
3108 |
SingletonList(E obj) {element = obj;} |
3109 |
|
3110 |
public int size() {return 1;} |
3111 |
|
3112 |
public boolean contains(Object obj) {return eq(obj, element);} |
3113 |
|
3114 |
public E get(int index) { |
3115 |
if (index != 0) |
3116 |
throw new IndexOutOfBoundsException("Index: "+index+", Size: 1"); |
3117 |
return element; |
3118 |
} |
3119 |
} |
3120 |
|
3121 |
/** |
3122 |
* Returns an immutable map, mapping only the specified key to the |
3123 |
* specified value. The returned map is serializable. |
3124 |
* |
3125 |
* @param key the sole key to be stored in the returned map. |
3126 |
* @param value the value to which the returned map maps <tt>key</tt>. |
3127 |
* @return an immutable map containing only the specified key-value |
3128 |
* mapping. |
3129 |
* @since 1.3 |
3130 |
*/ |
3131 |
public static <K,V> Map<K,V> singletonMap(K key, V value) { |
3132 |
return new SingletonMap<K,V>(key, value); |
3133 |
} |
3134 |
|
3135 |
private static class SingletonMap<K,V> |
3136 |
extends AbstractMap<K,V> |
3137 |
implements Serializable { |
3138 |
private static final long serialVersionUID = -6979724477215052911L; |
3139 |
|
3140 |
private final K k; |
3141 |
private final V v; |
3142 |
|
3143 |
SingletonMap(K key, V value) { |
3144 |
k = key; |
3145 |
v = value; |
3146 |
} |
3147 |
|
3148 |
public int size() {return 1;} |
3149 |
|
3150 |
public boolean isEmpty() {return false;} |
3151 |
|
3152 |
public boolean containsKey(Object key) {return eq(key, k);} |
3153 |
|
3154 |
public boolean containsValue(Object value) {return eq(value, v);} |
3155 |
|
3156 |
public V get(Object key) {return (eq(key, k) ? v : null);} |
3157 |
|
3158 |
private transient Set<K> keySet = null; |
3159 |
private transient Set<Map.Entry<K,V>> entrySet = null; |
3160 |
private transient Collection<V> values = null; |
3161 |
|
3162 |
public Set<K> keySet() { |
3163 |
if (keySet==null) |
3164 |
keySet = singleton(k); |
3165 |
return keySet; |
3166 |
} |
3167 |
|
3168 |
public Set<Map.Entry<K,V>> entrySet() { |
3169 |
if (entrySet==null) |
3170 |
entrySet = Collections.<Map.Entry<K,V>>singleton( |
3171 |
new SimpleImmutableEntry<K,V>(k, v)); |
3172 |
return entrySet; |
3173 |
} |
3174 |
|
3175 |
public Collection<V> values() { |
3176 |
if (values==null) |
3177 |
values = singleton(v); |
3178 |
return values; |
3179 |
} |
3180 |
|
3181 |
} |
3182 |
|
3183 |
/** |
3184 |
* Returns an immutable list consisting of <tt>n</tt> copies of the |
3185 |
* specified object. The newly allocated data object is tiny (it contains |
3186 |
* a single reference to the data object). This method is useful in |
3187 |
* combination with the <tt>List.addAll</tt> method to grow lists. |
3188 |
* The returned list is serializable. |
3189 |
* |
3190 |
* @param n the number of elements in the returned list. |
3191 |
* @param o the element to appear repeatedly in the returned list. |
3192 |
* @return an immutable list consisting of <tt>n</tt> copies of the |
3193 |
* specified object. |
3194 |
* @throws IllegalArgumentException if n < 0. |
3195 |
* @see List#addAll(Collection) |
3196 |
* @see List#addAll(int, Collection) |
3197 |
*/ |
3198 |
public static <T> List<T> nCopies(int n, T o) { |
3199 |
return new CopiesList<T>(n, o); |
3200 |
} |
3201 |
|
3202 |
/** |
3203 |
* @serial include |
3204 |
*/ |
3205 |
private static class CopiesList<E> |
3206 |
extends AbstractList<E> |
3207 |
implements RandomAccess, Serializable |
3208 |
{ |
3209 |
static final long serialVersionUID = 2739099268398711800L; |
3210 |
|
3211 |
int n; |
3212 |
E element; |
3213 |
|
3214 |
CopiesList(int n, E e) { |
3215 |
if (n < 0) |
3216 |
throw new IllegalArgumentException("List length = " + n); |
3217 |
this.n = n; |
3218 |
element = e; |
3219 |
} |
3220 |
|
3221 |
public int size() { |
3222 |
return n; |
3223 |
} |
3224 |
|
3225 |
public boolean contains(Object obj) { |
3226 |
return n != 0 && eq(obj, element); |
3227 |
} |
3228 |
|
3229 |
public E get(int index) { |
3230 |
if (index<0 || index>=n) |
3231 |
throw new IndexOutOfBoundsException("Index: "+index+ |
3232 |
", Size: "+n); |
3233 |
return element; |
3234 |
} |
3235 |
} |
3236 |
|
3237 |
/** |
3238 |
* Returns a comparator that imposes the reverse of the <i>natural |
3239 |
* ordering</i> on a collection of objects that implement the |
3240 |
* <tt>Comparable</tt> interface. (The natural ordering is the ordering |
3241 |
* imposed by the objects' own <tt>compareTo</tt> method.) This enables a |
3242 |
* simple idiom for sorting (or maintaining) collections (or arrays) of |
3243 |
* objects that implement the <tt>Comparable</tt> interface in |
3244 |
* reverse-natural-order. For example, suppose a is an array of |
3245 |
* strings. Then: <pre> |
3246 |
* Arrays.sort(a, Collections.reverseOrder()); |
3247 |
* </pre> sorts the array in reverse-lexicographic (alphabetical) order.<p> |
3248 |
* |
3249 |
* The returned comparator is serializable. |
3250 |
* |
3251 |
* @return a comparator that imposes the reverse of the <i>natural |
3252 |
* ordering</i> on a collection of objects that implement |
3253 |
* the <tt>Comparable</tt> interface. |
3254 |
* @see Comparable |
3255 |
*/ |
3256 |
public static <T> Comparator<T> reverseOrder() { |
3257 |
return (Comparator<T>) REVERSE_ORDER; |
3258 |
} |
3259 |
|
3260 |
private static final Comparator REVERSE_ORDER = new ReverseComparator(); |
3261 |
|
3262 |
/** |
3263 |
* @serial include |
3264 |
*/ |
3265 |
private static class ReverseComparator<T> |
3266 |
implements Comparator<Comparable<Object>>, Serializable { |
3267 |
|
3268 |
// use serialVersionUID from JDK 1.2.2 for interoperability |
3269 |
private static final long serialVersionUID = 7207038068494060240L; |
3270 |
|
3271 |
public int compare(Comparable<Object> c1, Comparable<Object> c2) { |
3272 |
return c2.compareTo(c1); |
3273 |
} |
3274 |
} |
3275 |
|
3276 |
/** |
3277 |
* Returns a comparator that imposes the reverse ordering of the specified |
3278 |
* comparator. If the specified comparator is null, this method is |
3279 |
* equivalent to {@link #reverseOrder()} (in other words, it returns a |
3280 |
* comparator that imposes the reverse of the <i>natural ordering</i> on a |
3281 |
* collection of objects that implement the Comparable interface). |
3282 |
* |
3283 |
* <p>The returned comparator is serializable (assuming the specified |
3284 |
* comparator is also serializable or null). |
3285 |
* |
3286 |
* @return a comparator that imposes the reverse ordering of the |
3287 |
* specified comparator. |
3288 |
* @since 1.5 |
3289 |
*/ |
3290 |
public static <T> Comparator<T> reverseOrder(Comparator<T> cmp) { |
3291 |
if (cmp == null) |
3292 |
return new ReverseComparator(); // Unchecked warning!! |
3293 |
|
3294 |
return new ReverseComparator2<T>(cmp); |
3295 |
} |
3296 |
|
3297 |
/** |
3298 |
* @serial include |
3299 |
*/ |
3300 |
private static class ReverseComparator2<T> implements Comparator<T>, |
3301 |
Serializable |
3302 |
{ |
3303 |
private static final long serialVersionUID = 4374092139857L; |
3304 |
|
3305 |
/** |
3306 |
* The comparator specified in the static factory. This will never |
3307 |
* be null, as the static factory returns a ReverseComparator |
3308 |
* instance if its argument is null. |
3309 |
* |
3310 |
* @serial |
3311 |
*/ |
3312 |
private Comparator<T> cmp; |
3313 |
|
3314 |
ReverseComparator2(Comparator<T> cmp) { |
3315 |
assert cmp != null; |
3316 |
this.cmp = cmp; |
3317 |
} |
3318 |
|
3319 |
public int compare(T t1, T t2) { |
3320 |
return cmp.compare(t2, t1); |
3321 |
} |
3322 |
} |
3323 |
|
3324 |
/** |
3325 |
* Returns an enumeration over the specified collection. This provides |
3326 |
* interoperability with legacy APIs that require an enumeration |
3327 |
* as input. |
3328 |
* |
3329 |
* @param c the collection for which an enumeration is to be returned. |
3330 |
* @return an enumeration over the specified collection. |
3331 |
* @see Enumeration |
3332 |
*/ |
3333 |
public static <T> Enumeration<T> enumeration(final Collection<T> c) { |
3334 |
return new Enumeration<T>() { |
3335 |
Iterator<T> i = c.iterator(); |
3336 |
|
3337 |
public boolean hasMoreElements() { |
3338 |
return i.hasNext(); |
3339 |
} |
3340 |
|
3341 |
public T nextElement() { |
3342 |
return i.next(); |
3343 |
} |
3344 |
}; |
3345 |
} |
3346 |
|
3347 |
/** |
3348 |
* Returns an array list containing the elements returned by the |
3349 |
* specified enumeration in the order they are returned by the |
3350 |
* enumeration. This method provides interoperability between |
3351 |
* legacy APIs that return enumerations and new APIs that require |
3352 |
* collections. |
3353 |
* |
3354 |
* @param e enumeration providing elements for the returned |
3355 |
* array list |
3356 |
* @return an array list containing the elements returned |
3357 |
* by the specified enumeration. |
3358 |
* @since 1.4 |
3359 |
* @see Enumeration |
3360 |
* @see ArrayList |
3361 |
*/ |
3362 |
public static <T> ArrayList<T> list(Enumeration<T> e) { |
3363 |
ArrayList<T> l = new ArrayList<T>(); |
3364 |
while (e.hasMoreElements()) |
3365 |
l.add(e.nextElement()); |
3366 |
return l; |
3367 |
} |
3368 |
|
3369 |
/** |
3370 |
* Returns true if the specified arguments are equal, or both null. |
3371 |
*/ |
3372 |
private static boolean eq(Object o1, Object o2) { |
3373 |
return (o1==null ? o2==null : o1.equals(o2)); |
3374 |
} |
3375 |
|
3376 |
/** |
3377 |
* Returns the number of elements in the specified collection equal to the |
3378 |
* specified object. More formally, returns the number of elements |
3379 |
* <tt>e</tt> in the collection such that |
3380 |
* <tt>(o == null ? e == null : o.equals(e))</tt>. |
3381 |
* |
3382 |
* @param c the collection in which to determine the frequency |
3383 |
* of <tt>o</tt> |
3384 |
* @param o the object whose frequency is to be determined |
3385 |
* @throws NullPointerException if <tt>c</tt> is null |
3386 |
* @since 1.5 |
3387 |
*/ |
3388 |
public static int frequency(Collection<?> c, Object o) { |
3389 |
int result = 0; |
3390 |
if (o == null) { |
3391 |
for (Object e : c) |
3392 |
if (e == null) |
3393 |
result++; |
3394 |
} else { |
3395 |
for (Object e : c) |
3396 |
if (o.equals(e)) |
3397 |
result++; |
3398 |
} |
3399 |
return result; |
3400 |
} |
3401 |
|
3402 |
/** |
3403 |
* Returns <tt>true</tt> if the two specified collections have no |
3404 |
* elements in common. |
3405 |
* |
3406 |
* <p>Care must be exercised if this method is used on collections that |
3407 |
* do not comply with the general contract for <tt>Collection</tt>. |
3408 |
* Implementations may elect to iterate over either collection and test |
3409 |
* for containment in the other collection (or to perform any equivalent |
3410 |
* computation). If either collection uses a nonstandard equality test |
3411 |
* (as does a {@link SortedSet} whose ordering is not <i>compatible with |
3412 |
* equals</i>, or the key set of an {@link IdentityHashMap}), both |
3413 |
* collections must use the same nonstandard equality test, or the |
3414 |
* result of this method is undefined. |
3415 |
* |
3416 |
* <p>Note that it is permissible to pass the same collection in both |
3417 |
* parameters, in which case the method will return true if and only if |
3418 |
* the collection is empty. |
3419 |
* |
3420 |
* @param c1 a collection |
3421 |
* @param c2 a collection |
3422 |
* @throws NullPointerException if either collection is null |
3423 |
* @since 1.5 |
3424 |
*/ |
3425 |
public static boolean disjoint(Collection<?> c1, Collection<?> c2) { |
3426 |
/* |
3427 |
* We're going to iterate through c1 and test for inclusion in c2. |
3428 |
* If c1 is a Set and c2 isn't, swap the collections. Otherwise, |
3429 |
* place the shorter collection in c1. Hopefully this heuristic |
3430 |
* will minimize the cost of the operation. |
3431 |
*/ |
3432 |
if ((c1 instanceof Set) && !(c2 instanceof Set) || |
3433 |
(c1.size() > c2.size())) { |
3434 |
Collection<?> tmp = c1; |
3435 |
c1 = c2; |
3436 |
c2 = tmp; |
3437 |
} |
3438 |
|
3439 |
for (Object e : c1) |
3440 |
if (c2.contains(e)) |
3441 |
return false; |
3442 |
return true; |
3443 |
} |
3444 |
|
3445 |
/** |
3446 |
* Adds all of the specified elements to the specified collection. |
3447 |
* Elements to be added may be specified individually or as an array. |
3448 |
* The behavior of this convenience method is identical to that of |
3449 |
* <tt>c.addAll(Arrays.asList(elements))</tt>, but this method is likely |
3450 |
* to run significantly faster under most implementations. |
3451 |
* |
3452 |
* <p>When elements are specified individually, this method provides a |
3453 |
* convenient way to add a few elements to an existing collection: |
3454 |
* <pre> |
3455 |
* Collections.addAll(flavors, "Peaches 'n Plutonium", "Rocky Racoon"); |
3456 |
* </pre> |
3457 |
* |
3458 |
* @param c the collection into which <tt>elements</tt> are to be inserted |
3459 |
* @param a the elements to insert into <tt>c</tt> |
3460 |
* @return <tt>true</tt> if the collection changed as a result of the call |
3461 |
* @throws UnsupportedOperationException if <tt>c</tt> does not support |
3462 |
* the <tt>add</tt> operation. |
3463 |
* @throws NullPointerException if <tt>elements</tt> contains one or more |
3464 |
* null values and <tt>c</tt> does not permit null elements, or |
3465 |
* if <tt>c</tt> or <tt>elements</tt> are <tt>null</tt> |
3466 |
* @throws IllegalArgumentException if some property of a value in |
3467 |
* <tt>elements</tt> prevents it from being added to <tt>c</tt> |
3468 |
* @see Collection#addAll(Collection) |
3469 |
* @since 1.5 |
3470 |
*/ |
3471 |
public static <T> boolean addAll(Collection<? super T> c, T... a) { |
3472 |
boolean result = false; |
3473 |
for (T e : a) |
3474 |
result |= c.add(e); |
3475 |
return result; |
3476 |
} |
3477 |
|
3478 |
/** |
3479 |
* Returns a set backed by the specified map. The resulting set displays |
3480 |
* the same ordering, concurrency, and performance characteristics as the |
3481 |
* backing map. In essence, this factory method provides a {@link Set} |
3482 |
* implementation corresponding to any {@link Map} implementation. There |
3483 |
* is no need to use this method on a {@link Map} implementation that |
3484 |
* already has a corresponding {@link Set} implementation (such as {@link |
3485 |
* HashMap} or {@link TreeMap}). |
3486 |
* |
3487 |
* <p>Each method invocation on the set returned by this method results in |
3488 |
* exactly one method invocation on the backing map or its <tt>keySet</tt> |
3489 |
* view, with one exception. The <tt>addAll</tt> method is implemented |
3490 |
* as a sequence of <tt>put</tt> invocations on the backing map. |
3491 |
* |
3492 |
* <p>The specified map must be empty at the time this method is invoked, |
3493 |
* and should not be accessed directly after this method returns. These |
3494 |
* conditions are ensured if the map is created empty, passed directly |
3495 |
* to this method, and no reference to the map is retained, as illustrated |
3496 |
* in the following code fragment: |
3497 |
* <pre> |
3498 |
* Set<Object> weakHashSet = Collections.asSet( |
3499 |
* new WeakHashMap<Object, Boolean>()); |
3500 |
* </pre> |
3501 |
* |
3502 |
* @param map the backing map |
3503 |
* @return the set backed by the map |
3504 |
* @throws IllegalArgumentException if <tt>map</tt> is not empty |
3505 |
*/ |
3506 |
public static <E> Set<E> asSet(Map<E, Boolean> map) { |
3507 |
return new MapAsSet<E>(map); |
3508 |
} |
3509 |
|
3510 |
private static class MapAsSet<E> extends AbstractSet<E> |
3511 |
implements Set<E>, Serializable |
3512 |
{ |
3513 |
private final Map<E, Boolean> m; // The backing map |
3514 |
private transient Set<E> keySet; // Its keySet |
3515 |
|
3516 |
MapAsSet(Map<E, Boolean> map) { |
3517 |
if (!map.isEmpty()) |
3518 |
throw new IllegalArgumentException("Map is non-empty"); |
3519 |
m = map; |
3520 |
keySet = map.keySet(); |
3521 |
} |
3522 |
|
3523 |
public int size() { return m.size(); } |
3524 |
public boolean isEmpty() { return m.isEmpty(); } |
3525 |
public boolean contains(Object o) { return m.containsKey(o); } |
3526 |
public Iterator<E> iterator() { return keySet.iterator(); } |
3527 |
public Object[] toArray() { return keySet.toArray(); } |
3528 |
public <T> T[] toArray(T[] a) { return keySet.toArray(a); } |
3529 |
public boolean add(E e) { |
3530 |
return m.put(e, Boolean.TRUE) == null; |
3531 |
} |
3532 |
public boolean remove(Object o) { return m.remove(o) != null; } |
3533 |
|
3534 |
public boolean removeAll(Collection<?> c) { |
3535 |
return keySet.removeAll(c); |
3536 |
} |
3537 |
public boolean retainAll(Collection<?> c) { |
3538 |
return keySet.retainAll(c); |
3539 |
} |
3540 |
public void clear() { m.clear(); } |
3541 |
public boolean equals(Object o) { return keySet.equals(o); } |
3542 |
public int hashCode() { return keySet.hashCode(); } |
3543 |
|
3544 |
private static final long serialVersionUID = 2454657854757543876L; |
3545 |
|
3546 |
private void readObject(java.io.ObjectInputStream s) |
3547 |
throws IOException, ClassNotFoundException |
3548 |
{ |
3549 |
s.defaultReadObject(); |
3550 |
keySet = m.keySet(); |
3551 |
} |
3552 |
} |
3553 |
|
3554 |
/** |
3555 |
* Returns a view of a {@link Deque} as a Last-in-first-out (Lifo) |
3556 |
* {@link Queue}. Method <tt>add</tt> is mapped to <tt>push</tt>, |
3557 |
* <tt>remove</tt> is mapped to <tt>pop</tt> and so on. This |
3558 |
* view can be useful when you would like to use a method |
3559 |
* requiring a <tt>Queue</tt> but you need Lifo ordering. |
3560 |
* @param deque the Deque |
3561 |
* @return the queue |
3562 |
* @since 1.6 |
3563 |
*/ |
3564 |
public static <T> Queue<T> asLifoQueue(Deque<T> deque) { |
3565 |
return new AsLIFOQueue<T>(deque); |
3566 |
} |
3567 |
|
3568 |
static class AsLIFOQueue<E> extends AbstractQueue<E> |
3569 |
implements Queue<E>, Serializable { |
3570 |
private static final long serialVersionUID = 1802017725587941708L; |
3571 |
private final Deque<E> q; |
3572 |
AsLIFOQueue(Deque<E> q) { this.q = q; } |
3573 |
public boolean offer(E e) { return q.offerFirst(e); } |
3574 |
public E poll() { return q.pollFirst(); } |
3575 |
public E remove() { return q.removeFirst(); } |
3576 |
public E peek() { return q.peekFirst(); } |
3577 |
public E element() { return q.getFirst(); } |
3578 |
public int size() { return q.size(); } |
3579 |
public boolean isEmpty() { return q.isEmpty(); } |
3580 |
public boolean contains(Object o) { return q.contains(o); } |
3581 |
public Iterator<E> iterator() { return q.iterator(); } |
3582 |
public Object[] toArray() { return q.toArray(); } |
3583 |
public <T> T[] toArray(T[] a) { return q.toArray(a); } |
3584 |
public boolean add(E e) { return q.offerFirst(e); } |
3585 |
public boolean remove(Object o) { return q.remove(o); } |
3586 |
public void clear() { q.clear(); } |
3587 |
} |
3588 |
} |