1 |
/* |
2 |
* Written by Doug Lea with assistance from members of JCP JSR-166 |
3 |
* Expert Group. Adapted and released, under explicit permission, |
4 |
* from JDK ArrayList.java which carries the following copyright: |
5 |
* |
6 |
* Copyright 1997 by Sun Microsystems, Inc., |
7 |
* 901 San Antonio Road, Palo Alto, California, 94303, U.S.A. |
8 |
* All rights reserved. |
9 |
* |
10 |
* This software is the confidential and proprietary information |
11 |
* of Sun Microsystems, Inc. ("Confidential Information"). You |
12 |
* shall not disclose such Confidential Information and shall use |
13 |
* it only in accordance with the terms of the license agreement |
14 |
* you entered into with Sun. |
15 |
*/ |
16 |
|
17 |
package java.util.concurrent; |
18 |
import java.util.*; |
19 |
|
20 |
/** |
21 |
* A thread-safe variant of {@link java.util.ArrayList} in which all mutative |
22 |
* operations (<tt>add</tt>, <tt>set</tt>, and so on) are implemented by |
23 |
* making a fresh copy of the underlying array. |
24 |
* |
25 |
* <p> This is ordinarily too costly, but may be <em>more</em> efficient |
26 |
* than alternatives when traversal operations vastly outnumber |
27 |
* mutations, and is useful when you cannot or don't want to |
28 |
* synchronize traversals, yet need to preclude interference among |
29 |
* concurrent threads. The "snapshot" style iterator method uses a |
30 |
* reference to the state of the array at the point that the iterator |
31 |
* was created. This array never changes during the lifetime of the |
32 |
* iterator, so interference is impossible and the iterator is |
33 |
* guaranteed not to throw <tt>ConcurrentModificationException</tt>. |
34 |
* The iterator will not reflect additions, removals, or changes to |
35 |
* the list since the iterator was created. Element-changing |
36 |
* operations on iterators themselves (<tt>remove</tt>, <tt>set</tt>, and |
37 |
* <tt>add</tt>) are not supported. These methods throw |
38 |
* <tt>UnsupportedOperationException</tt>. |
39 |
* |
40 |
* <p>All elements are permitted, including <tt>null</tt>. |
41 |
* |
42 |
* <p>This class is a member of the |
43 |
* <a href="{@docRoot}/../guide/collections/index.html"> |
44 |
* Java Collections Framework</a>. |
45 |
* |
46 |
* @since 1.5 |
47 |
* @author Doug Lea |
48 |
* @param <E> the type of elements held in this collection |
49 |
*/ |
50 |
public class CopyOnWriteArrayList<E> |
51 |
implements List<E>, RandomAccess, Cloneable, java.io.Serializable { |
52 |
private static final long serialVersionUID = 8673264195747942595L; |
53 |
|
54 |
/** |
55 |
* The held array. Directly accessed only within synchronized |
56 |
* methods. |
57 |
*/ |
58 |
private volatile transient E[] array; |
59 |
|
60 |
/** |
61 |
* Accessor to the array intended to be called from |
62 |
* within unsynchronized read-only methods |
63 |
*/ |
64 |
private E[] array() { return array; } |
65 |
|
66 |
/** |
67 |
* Creates an empty list. |
68 |
*/ |
69 |
public CopyOnWriteArrayList() { |
70 |
array = (E[]) new Object[0]; |
71 |
} |
72 |
|
73 |
/** |
74 |
* Creates a list containing the elements of the specified |
75 |
* collection, in the order they are returned by the collection's |
76 |
* iterator. |
77 |
* |
78 |
* @param c the collection of initially held elements |
79 |
* @throws NullPointerException if the specified collection is null |
80 |
*/ |
81 |
public CopyOnWriteArrayList(Collection<? extends E> c) { |
82 |
array = (E[]) new Object[c.size()]; |
83 |
Iterator<? extends E> i = c.iterator(); |
84 |
int size = 0; |
85 |
while (i.hasNext()) |
86 |
array[size++] = i.next(); |
87 |
} |
88 |
|
89 |
/** |
90 |
* Creates a list holding a copy of the given array. |
91 |
* |
92 |
* @param toCopyIn the array (a copy of this array is used as the |
93 |
* internal array) |
94 |
* @throws NullPointerException if the specified array is null |
95 |
*/ |
96 |
public CopyOnWriteArrayList(E[] toCopyIn) { |
97 |
copyIn(toCopyIn, 0, toCopyIn.length); |
98 |
} |
99 |
|
100 |
/** |
101 |
* Replaces the held array with a copy of the <tt>n</tt> elements |
102 |
* of the provided array, starting at position <tt>first</tt>. To |
103 |
* copy an entire array, call with arguments (array, 0, |
104 |
* array.length). |
105 |
* @param toCopyIn the array. A copy of the indicated elements of |
106 |
* this array is used as the internal array. |
107 |
* @param first The index of first position of the array to |
108 |
* start copying from. |
109 |
* @param n the number of elements to copy. This will be the new size of |
110 |
* the list. |
111 |
*/ |
112 |
private synchronized void copyIn(E[] toCopyIn, int first, int n) { |
113 |
array = (E[]) new Object[n]; |
114 |
System.arraycopy(toCopyIn, first, array, 0, n); |
115 |
} |
116 |
|
117 |
/** |
118 |
* Returns the number of elements in this list. |
119 |
* |
120 |
* @return the number of elements in this list |
121 |
*/ |
122 |
public int size() { |
123 |
return array().length; |
124 |
} |
125 |
|
126 |
/** |
127 |
* Returns <tt>true</tt> if this list contains no elements. |
128 |
* |
129 |
* @return <tt>true</tt> if this list contains no elements |
130 |
*/ |
131 |
public boolean isEmpty() { |
132 |
return size() == 0; |
133 |
} |
134 |
|
135 |
/** |
136 |
* Returns <tt>true</tt> if this list contains the specified element. |
137 |
* More formally, returns <tt>true</tt> if and only if this list contains |
138 |
* at least one element <tt>e</tt> such that |
139 |
* <tt>(o==null ? e==null : o.equals(e))</tt>. |
140 |
* |
141 |
* @param o element whose presence in this list is to be tested |
142 |
* @return <tt>true</tt> if this list contains the specified element |
143 |
*/ |
144 |
public boolean contains(Object o) { |
145 |
E[] elementData = array(); |
146 |
int len = elementData.length; |
147 |
return indexOf(o, elementData, len) >= 0; |
148 |
} |
149 |
|
150 |
/** |
151 |
* {@inheritDoc} |
152 |
*/ |
153 |
public int indexOf(Object o) { |
154 |
E[] elementData = array(); |
155 |
int len = elementData.length; |
156 |
return indexOf(o, elementData, len); |
157 |
} |
158 |
|
159 |
/** |
160 |
* static version allows repeated call without needing |
161 |
* to grab lock for array each time |
162 |
*/ |
163 |
private static int indexOf(Object o, Object[] elementData, int len) { |
164 |
if (o == null) { |
165 |
for (int i = 0; i < len; i++) |
166 |
if (elementData[i]==null) |
167 |
return i; |
168 |
} else { |
169 |
for (int i = 0; i < len; i++) |
170 |
if (o.equals(elementData[i])) |
171 |
return i; |
172 |
} |
173 |
return -1; |
174 |
} |
175 |
|
176 |
/** |
177 |
* Returns the index of the first occurrence of the specified element in |
178 |
* this list, searching forwards from <tt>index</tt>, or returns -1 if |
179 |
* the element is not found. |
180 |
* More formally, returns the lowest index <tt>i</tt> such that |
181 |
* <tt>(i >= index && (e==null ? get(i)==null : e.equals(get(i))))</tt>, |
182 |
* or -1 if there is no such index. |
183 |
* |
184 |
* @param e element to search for |
185 |
* @param index index to start searching from |
186 |
* @return the index of the first occurrence of the element in |
187 |
* this list at position <tt>index</tt> or later in the list; |
188 |
* <tt>-1</tt> if the element is not found. |
189 |
* @throws IndexOutOfBoundsException if the specified index is negative |
190 |
*/ |
191 |
public int indexOf(E e, int index) { |
192 |
E[] elementData = array(); |
193 |
int elementCount = elementData.length; |
194 |
|
195 |
if (e == null) { |
196 |
for (int i = index ; i < elementCount ; i++) |
197 |
if (elementData[i]==null) |
198 |
return i; |
199 |
} else { |
200 |
for (int i = index ; i < elementCount ; i++) |
201 |
if (e.equals(elementData[i])) |
202 |
return i; |
203 |
} |
204 |
return -1; |
205 |
} |
206 |
|
207 |
/** |
208 |
* {@inheritDoc} |
209 |
*/ |
210 |
public int lastIndexOf(Object o) { |
211 |
E[] elementData = array(); |
212 |
int len = elementData.length; |
213 |
return lastIndexOf(o, elementData, len); |
214 |
} |
215 |
|
216 |
private static int lastIndexOf(Object o, Object[] elementData, int len) { |
217 |
if (o == null) { |
218 |
for (int i = len-1; i >= 0; i--) |
219 |
if (elementData[i]==null) |
220 |
return i; |
221 |
} else { |
222 |
for (int i = len-1; i >= 0; i--) |
223 |
if (o.equals(elementData[i])) |
224 |
return i; |
225 |
} |
226 |
return -1; |
227 |
} |
228 |
|
229 |
/** |
230 |
* Returns the index of the last occurrence of the specified element in |
231 |
* this list, searching backwards from <tt>index</tt>, or returns -1 if |
232 |
* the element is not found. |
233 |
* More formally, returns the highest index <tt>i</tt> such that |
234 |
* <tt>(i <= index && (e==null ? get(i)==null : e.equals(get(i))))</tt>, |
235 |
* or -1 if there is no such index. |
236 |
* |
237 |
* @param e element to search for |
238 |
* @param index index to start searching backwards from |
239 |
* @return the index of the last occurrence of the element at position |
240 |
* less than or equal to <tt>index</tt> in this list; |
241 |
* -1 if the element is not found. |
242 |
* @throws IndexOutOfBoundsException if the specified index is greater |
243 |
* than or equal to the current size of this list |
244 |
*/ |
245 |
public int lastIndexOf(E e, int index) { |
246 |
// needed in order to compile on 1.2b3 |
247 |
E[] elementData = array(); |
248 |
if (e == null) { |
249 |
for (int i = index; i >= 0; i--) |
250 |
if (elementData[i]==null) |
251 |
return i; |
252 |
} else { |
253 |
for (int i = index; i >= 0; i--) |
254 |
if (e.equals(elementData[i])) |
255 |
return i; |
256 |
} |
257 |
return -1; |
258 |
} |
259 |
|
260 |
/** |
261 |
* Returns a shallow copy of this list. (The elements themselves |
262 |
* are not copied.) |
263 |
* |
264 |
* @return a clone of this list |
265 |
*/ |
266 |
public Object clone() { |
267 |
try { |
268 |
E[] elementData = array(); |
269 |
CopyOnWriteArrayList<E> v = (CopyOnWriteArrayList<E>)super.clone(); |
270 |
v.array = (E[]) new Object[elementData.length]; |
271 |
System.arraycopy(elementData, 0, v.array, 0, elementData.length); |
272 |
return v; |
273 |
} catch (CloneNotSupportedException e) { |
274 |
// this shouldn't happen, since we are Cloneable |
275 |
throw new InternalError(); |
276 |
} |
277 |
} |
278 |
|
279 |
/** |
280 |
* Returns an array containing all of the elements in this list |
281 |
* in proper sequence (from first to last element). |
282 |
* |
283 |
* <p>The returned array will be "safe" in that no references to it are |
284 |
* maintained by this list. (In other words, this method must allocate |
285 |
* a new array). The caller is thus free to modify the returned array. |
286 |
* |
287 |
* <p>This method acts as bridge between array-based and collection-based |
288 |
* APIs. |
289 |
* |
290 |
* @return an array containing all the elements in this list |
291 |
*/ |
292 |
public Object[] toArray() { |
293 |
Object[] elementData = array(); |
294 |
Object[] result = new Object[elementData.length]; |
295 |
System.arraycopy(elementData, 0, result, 0, elementData.length); |
296 |
return result; |
297 |
} |
298 |
|
299 |
/** |
300 |
* Returns an array containing all of the elements in this list in |
301 |
* proper sequence (from first to last element); the runtime type of |
302 |
* the returned array is that of the specified array. If the list fits |
303 |
* in the specified array, it is returned therein. Otherwise, a new |
304 |
* array is allocated with the runtime type of the specified array and |
305 |
* the size of this list. |
306 |
* |
307 |
* <p>If this list fits in the specified array with room to spare |
308 |
* (i.e., the array has more elements than this list), the element in |
309 |
* the array immediately following the end of the list is set to |
310 |
* <tt>null</tt>. (This is useful in determining the length of this |
311 |
* list <i>only</i> if the caller knows that this list does not contain |
312 |
* any null elements.) |
313 |
* |
314 |
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
315 |
* array-based and collection-based APIs. Further, this method allows |
316 |
* precise control over the runtime type of the output array, and may, |
317 |
* under certain circumstances, be used to save allocation costs. |
318 |
* |
319 |
* <p>Suppose <tt>x</tt> is a list known to contain only strings. |
320 |
* The following code can be used to dump the list into a newly |
321 |
* allocated array of <tt>String</tt>: |
322 |
* |
323 |
* <pre> |
324 |
* String[] y = x.toArray(new String[0]);</pre> |
325 |
* |
326 |
* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
327 |
* <tt>toArray()</tt>. |
328 |
* |
329 |
* @param a the array into which the elements of the list are to |
330 |
* be stored, if it is big enough; otherwise, a new array of the |
331 |
* same runtime type is allocated for this purpose. |
332 |
* @return an array containing all the elements in this list |
333 |
* @throws ArrayStoreException if the runtime type of the specified array |
334 |
* is not a supertype of the runtime type of every element in |
335 |
* this list |
336 |
* @throws NullPointerException if the specified array is null |
337 |
*/ |
338 |
public <T> T[] toArray(T a[]) { |
339 |
E[] elementData = array(); |
340 |
|
341 |
if (a.length < elementData.length) |
342 |
a = (T[]) |
343 |
java.lang.reflect.Array.newInstance(a.getClass().getComponentType(), |
344 |
elementData.length); |
345 |
|
346 |
System.arraycopy(elementData, 0, a, 0, elementData.length); |
347 |
|
348 |
if (a.length > elementData.length) |
349 |
a[elementData.length] = null; |
350 |
|
351 |
return a; |
352 |
} |
353 |
|
354 |
// Positional Access Operations |
355 |
|
356 |
/** |
357 |
* {@inheritDoc} |
358 |
* |
359 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
360 |
*/ |
361 |
public E get(int index) { |
362 |
E[] elementData = array(); |
363 |
rangeCheck(index, elementData.length); |
364 |
return elementData[index]; |
365 |
} |
366 |
|
367 |
/** |
368 |
* Replaces the element at the specified position in this list with the |
369 |
* specified element. |
370 |
* |
371 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
372 |
*/ |
373 |
public synchronized E set(int index, E element) { |
374 |
int len = array.length; |
375 |
rangeCheck(index, len); |
376 |
E oldValue = array[index]; |
377 |
|
378 |
boolean same = (oldValue == element || |
379 |
(element != null && element.equals(oldValue))); |
380 |
if (!same) { |
381 |
E[] newArray = (E[]) new Object[len]; |
382 |
System.arraycopy(array, 0, newArray, 0, len); |
383 |
newArray[index] = element; |
384 |
array = newArray; |
385 |
} |
386 |
return oldValue; |
387 |
} |
388 |
|
389 |
/** |
390 |
* Appends the specified element to the end of this list. |
391 |
* |
392 |
* @param element element to be appended to this list |
393 |
* @return <tt>true</tt> (as per the spec for {@link Collection#add}) |
394 |
*/ |
395 |
public synchronized boolean add(E element) { |
396 |
int len = array.length; |
397 |
E[] newArray = (E[]) new Object[len+1]; |
398 |
System.arraycopy(array, 0, newArray, 0, len); |
399 |
newArray[len] = element; |
400 |
array = newArray; |
401 |
return true; |
402 |
} |
403 |
|
404 |
/** |
405 |
* Inserts the specified element at the specified position in this |
406 |
* list. Shifts the element currently at that position (if any) and |
407 |
* any subsequent elements to the right (adds one to their indices). |
408 |
* |
409 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
410 |
*/ |
411 |
public synchronized void add(int index, E element) { |
412 |
int len = array.length; |
413 |
if (index > len || index < 0) |
414 |
throw new IndexOutOfBoundsException("Index: "+index+", Size: "+len); |
415 |
|
416 |
E[] newArray = (E[]) new Object[len+1]; |
417 |
System.arraycopy(array, 0, newArray, 0, index); |
418 |
newArray[index] = element; |
419 |
System.arraycopy(array, index, newArray, index+1, len - index); |
420 |
array = newArray; |
421 |
} |
422 |
|
423 |
/** |
424 |
* Removes the element at the specified position in this list. |
425 |
* Shifts any subsequent elements to the left (subtracts one from their |
426 |
* indices). Returns the element that was removed from the list. |
427 |
* |
428 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
429 |
*/ |
430 |
public synchronized E remove(int index) { |
431 |
int len = array.length; |
432 |
rangeCheck(index, len); |
433 |
E oldValue = array[index]; |
434 |
E[] newArray = (E[]) new Object[len-1]; |
435 |
System.arraycopy(array, 0, newArray, 0, index); |
436 |
int numMoved = len - index - 1; |
437 |
if (numMoved > 0) |
438 |
System.arraycopy(array, index+1, newArray, index, numMoved); |
439 |
array = newArray; |
440 |
return oldValue; |
441 |
} |
442 |
|
443 |
/** |
444 |
* Removes the first occurrence of the specified element from this list, |
445 |
* if it is present. If this list does not contain the element, it is |
446 |
* unchanged. More formally, removes the element with the lowest index |
447 |
* <tt>i</tt> such that |
448 |
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt> |
449 |
* (if such an element exists). Returns <tt>true</tt> if this list |
450 |
* contained the specified element (or equivalently, if this list |
451 |
* changed as a result of the call). |
452 |
* |
453 |
* @param o element to be removed from this list, if present |
454 |
* @return <tt>true</tt> if this list contained the specified element |
455 |
*/ |
456 |
public synchronized boolean remove(Object o) { |
457 |
int len = array.length; |
458 |
if (len == 0) return false; |
459 |
|
460 |
// Copy while searching for element to remove |
461 |
// This wins in the normal case of element being present |
462 |
|
463 |
int newlen = len-1; |
464 |
E[] newArray = (E[]) new Object[newlen]; |
465 |
|
466 |
for (int i = 0; i < newlen; ++i) { |
467 |
if (o == array[i] || |
468 |
(o != null && o.equals(array[i]))) { |
469 |
// found one; copy remaining and exit |
470 |
for (int k = i + 1; k < len; ++k) newArray[k-1] = array[k]; |
471 |
array = newArray; |
472 |
return true; |
473 |
} else |
474 |
newArray[i] = array[i]; |
475 |
} |
476 |
// special handling for last cell |
477 |
|
478 |
if (o == array[newlen] || |
479 |
(o != null && o.equals(array[newlen]))) { |
480 |
array = newArray; |
481 |
return true; |
482 |
} else |
483 |
return false; // throw away copy |
484 |
} |
485 |
|
486 |
/** |
487 |
* Removes from this list all of the elements whose index is between |
488 |
* <tt>fromIndex</tt>, inclusive, and <tt>toIndex</tt>, exclusive. |
489 |
* Shifts any succeeding elements to the left (reduces their index). |
490 |
* This call shortens the list by <tt>(toIndex - fromIndex)</tt> elements. |
491 |
* (If <tt>toIndex==fromIndex</tt>, this operation has no effect.) |
492 |
* |
493 |
* @param fromIndex index of first element to be removed |
494 |
* @param toIndex index after last element to be removed |
495 |
* @throws IndexOutOfBoundsException if fromIndex or toIndex out of |
496 |
* range (fromIndex < 0 || fromIndex >= size() || toIndex |
497 |
* > size() || toIndex < fromIndex) |
498 |
*/ |
499 |
private synchronized void removeRange(int fromIndex, int toIndex) { |
500 |
int len = array.length; |
501 |
|
502 |
if (fromIndex < 0 || fromIndex >= len || |
503 |
toIndex > len || toIndex < fromIndex) |
504 |
throw new IndexOutOfBoundsException(); |
505 |
|
506 |
int numMoved = len - toIndex; |
507 |
int newlen = len - (toIndex-fromIndex); |
508 |
E[] newArray = (E[]) new Object[newlen]; |
509 |
System.arraycopy(array, 0, newArray, 0, fromIndex); |
510 |
System.arraycopy(array, toIndex, newArray, fromIndex, numMoved); |
511 |
array = newArray; |
512 |
} |
513 |
|
514 |
/** |
515 |
* Append the element if not present. |
516 |
* |
517 |
* @param element element to be added to this list, if absent |
518 |
* @return <tt>true</tt> if the element was added |
519 |
*/ |
520 |
public synchronized boolean addIfAbsent(E element) { |
521 |
// Copy while checking if already present. |
522 |
// This wins in the most common case where it is not present |
523 |
int len = array.length; |
524 |
E[] newArray = (E[]) new Object[len + 1]; |
525 |
for (int i = 0; i < len; ++i) { |
526 |
if (element == array[i] || |
527 |
(element != null && element.equals(array[i]))) |
528 |
return false; // exit, throwing away copy |
529 |
else |
530 |
newArray[i] = array[i]; |
531 |
} |
532 |
newArray[len] = element; |
533 |
array = newArray; |
534 |
return true; |
535 |
} |
536 |
|
537 |
/** |
538 |
* Returns <tt>true</tt> if this list contains all of the elements of the |
539 |
* specified collection. |
540 |
* |
541 |
* @param c collection to be checked for containment in this list |
542 |
* @return <tt>true</tt> if this list contains all of the elements of the |
543 |
* specified collection |
544 |
* @throws NullPointerException if the specified collection is null |
545 |
* @see #contains(Object) |
546 |
*/ |
547 |
public boolean containsAll(Collection<?> c) { |
548 |
E[] elementData = array(); |
549 |
int len = elementData.length; |
550 |
Iterator e = c.iterator(); |
551 |
while (e.hasNext()) |
552 |
if (indexOf(e.next(), elementData, len) < 0) |
553 |
return false; |
554 |
|
555 |
return true; |
556 |
} |
557 |
|
558 |
/** |
559 |
* Removes from this list all of its elements that are contained in |
560 |
* the specified collection. This is a particularly expensive operation |
561 |
* in this class because of the need for an internal temporary array. |
562 |
* |
563 |
* @param c collection containing elements to be removed from this list |
564 |
* @return <tt>true</tt> if this list changed as a result of the call |
565 |
* @throws ClassCastException if the class of an element of this list |
566 |
* is incompatible with the specified collection (optional) |
567 |
* @throws NullPointerException if this list contains a null element and the |
568 |
* specified collection does not permit null elements (optional), |
569 |
* or if the specified collection is null |
570 |
* @see #remove(Object) |
571 |
*/ |
572 |
public synchronized boolean removeAll(Collection<?> c) { |
573 |
E[] elementData = array; |
574 |
int len = elementData.length; |
575 |
if (len == 0) return false; |
576 |
|
577 |
// temp array holds those elements we know we want to keep |
578 |
E[] temp = (E[]) new Object[len]; |
579 |
int newlen = 0; |
580 |
for (int i = 0; i < len; ++i) { |
581 |
E element = elementData[i]; |
582 |
if (!c.contains(element)) { |
583 |
temp[newlen++] = element; |
584 |
} |
585 |
} |
586 |
|
587 |
if (newlen == len) return false; |
588 |
|
589 |
// copy temp as new array |
590 |
E[] newArray = (E[]) new Object[newlen]; |
591 |
System.arraycopy(temp, 0, newArray, 0, newlen); |
592 |
array = newArray; |
593 |
return true; |
594 |
} |
595 |
|
596 |
/** |
597 |
* Retains only the elements in this list that are contained in the |
598 |
* specified collection. In other words, removes from this list all of |
599 |
* its elements that are not contained in the specified collection. |
600 |
* |
601 |
* @param c collection containing elements to be retained in this list |
602 |
* @return <tt>true</tt> if this list changed as a result of the call |
603 |
* @throws ClassCastException if the class of an element of this list |
604 |
* is incompatible with the specified collection (optional) |
605 |
* @throws NullPointerException if this list contains a null element and the |
606 |
* specified collection does not permit null elements (optional), |
607 |
* or if the specified collection is null |
608 |
* @see #remove(Object) |
609 |
*/ |
610 |
public synchronized boolean retainAll(Collection<?> c) { |
611 |
E[] elementData = array; |
612 |
int len = elementData.length; |
613 |
if (len == 0) return false; |
614 |
|
615 |
E[] temp = (E[]) new Object[len]; |
616 |
int newlen = 0; |
617 |
for (int i = 0; i < len; ++i) { |
618 |
E element = elementData[i]; |
619 |
if (c.contains(element)) { |
620 |
temp[newlen++] = element; |
621 |
} |
622 |
} |
623 |
|
624 |
if (newlen == len) return false; |
625 |
|
626 |
E[] newArray = (E[]) new Object[newlen]; |
627 |
System.arraycopy(temp, 0, newArray, 0, newlen); |
628 |
array = newArray; |
629 |
return true; |
630 |
} |
631 |
|
632 |
/** |
633 |
* Appends all of the elements in the specified collection that |
634 |
* are not already contained in this list, to the end of |
635 |
* this list, in the order that they are returned by the |
636 |
* specified collection's iterator. |
637 |
* |
638 |
* @param c collection containing elements to be added to this list |
639 |
* @return the number of elements added |
640 |
* @throws NullPointerException if the specified collection is null |
641 |
* @see #addIfAbsent(Object) |
642 |
*/ |
643 |
public synchronized int addAllAbsent(Collection<? extends E> c) { |
644 |
int numNew = c.size(); |
645 |
if (numNew == 0) return 0; |
646 |
|
647 |
E[] elementData = array; |
648 |
int len = elementData.length; |
649 |
|
650 |
E[] temp = (E[]) new Object[numNew]; |
651 |
int added = 0; |
652 |
Iterator<? extends E> e = c.iterator(); |
653 |
while (e.hasNext()) { |
654 |
E element = e.next(); |
655 |
if (indexOf(element, elementData, len) < 0) { |
656 |
if (indexOf(element, temp, added) < 0) { |
657 |
temp[added++] = element; |
658 |
} |
659 |
} |
660 |
} |
661 |
|
662 |
if (added == 0) return 0; |
663 |
|
664 |
E[] newArray = (E[]) new Object[len+added]; |
665 |
System.arraycopy(elementData, 0, newArray, 0, len); |
666 |
System.arraycopy(temp, 0, newArray, len, added); |
667 |
array = newArray; |
668 |
return added; |
669 |
} |
670 |
|
671 |
/** |
672 |
* Removes all of the elements from this list. |
673 |
* The list will be empty after this call returns. |
674 |
*/ |
675 |
public synchronized void clear() { |
676 |
array = (E[]) new Object[0]; |
677 |
} |
678 |
|
679 |
/** |
680 |
* Appends all of the elements in the specified collection to the end |
681 |
* of this list, in the order that they are returned by the specified |
682 |
* collection's iterator. |
683 |
* |
684 |
* @param c collection containing elements to be added to this list |
685 |
* @return <tt>true</tt> if this list changed as a result of the call |
686 |
* @throws NullPointerException if the specified collection is null |
687 |
* @see #add(Object) |
688 |
*/ |
689 |
public synchronized boolean addAll(Collection<? extends E> c) { |
690 |
int numNew = c.size(); |
691 |
if (numNew == 0) return false; |
692 |
|
693 |
int len = array.length; |
694 |
E[] newArray = (E[]) new Object[len+numNew]; |
695 |
System.arraycopy(array, 0, newArray, 0, len); |
696 |
Iterator<? extends E> e = c.iterator(); |
697 |
for (int i=0; i<numNew; i++) |
698 |
newArray[len++] = e.next(); |
699 |
array = newArray; |
700 |
|
701 |
return true; |
702 |
} |
703 |
|
704 |
/** |
705 |
* Inserts all of the elements in the specified collection into this |
706 |
* list, starting at the specified position. Shifts the element |
707 |
* currently at that position (if any) and any subsequent elements to |
708 |
* the right (increases their indices). The new elements will appear |
709 |
* in this list in the order that they are returned by the |
710 |
* specified collection's iterator. |
711 |
* |
712 |
* @param index index at which to insert the first element |
713 |
* from the specified collection |
714 |
* @param c collection containing elements to be added to this list |
715 |
* @return <tt>true</tt> if this list changed as a result of the call |
716 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
717 |
* @throws NullPointerException if the specified collection is null |
718 |
* @see #add(int,Object) |
719 |
*/ |
720 |
public synchronized boolean addAll(int index, Collection<? extends E> c) { |
721 |
int len = array.length; |
722 |
if (index > len || index < 0) |
723 |
throw new IndexOutOfBoundsException("Index: "+index+", Size: "+len); |
724 |
|
725 |
int numNew = c.size(); |
726 |
if (numNew == 0) return false; |
727 |
|
728 |
E[] newArray = (E[]) new Object[len+numNew]; |
729 |
System.arraycopy(array, 0, newArray, 0, len); |
730 |
int numMoved = len - index; |
731 |
if (numMoved > 0) |
732 |
System.arraycopy(array, index, newArray, index + numNew, numMoved); |
733 |
Iterator<? extends E> e = c.iterator(); |
734 |
for (int i=0; i<numNew; i++) |
735 |
newArray[index++] = e.next(); |
736 |
array = newArray; |
737 |
|
738 |
return true; |
739 |
} |
740 |
|
741 |
/** |
742 |
* Checks if the given index is in range. If not, throws an appropriate |
743 |
* runtime exception. |
744 |
*/ |
745 |
private void rangeCheck(int index, int length) { |
746 |
if (index >= length || index < 0) |
747 |
throw new IndexOutOfBoundsException("Index: "+index+", Size: "+ length); |
748 |
} |
749 |
|
750 |
/** |
751 |
* Save the state of the list to a stream (i.e., serialize it). |
752 |
* |
753 |
* @serialData The length of the array backing the list is emitted |
754 |
* (int), followed by all of its elements (each an Object) |
755 |
* in the proper order. |
756 |
* @param s the stream |
757 |
*/ |
758 |
private void writeObject(java.io.ObjectOutputStream s) |
759 |
throws java.io.IOException{ |
760 |
|
761 |
// Write out element count, and any hidden stuff |
762 |
s.defaultWriteObject(); |
763 |
|
764 |
E[] elementData = array(); |
765 |
// Write out array length |
766 |
s.writeInt(elementData.length); |
767 |
|
768 |
// Write out all elements in the proper order. |
769 |
for (int i=0; i<elementData.length; i++) |
770 |
s.writeObject(elementData[i]); |
771 |
} |
772 |
|
773 |
/** |
774 |
* Reconstitute the list from a stream (i.e., deserialize it). |
775 |
* @param s the stream |
776 |
*/ |
777 |
private void readObject(java.io.ObjectInputStream s) |
778 |
throws java.io.IOException, ClassNotFoundException { |
779 |
|
780 |
// Read in size, and any hidden stuff |
781 |
s.defaultReadObject(); |
782 |
|
783 |
// Read in array length and allocate array |
784 |
int arrayLength = s.readInt(); |
785 |
E[] elementData = (E[]) new Object[arrayLength]; |
786 |
|
787 |
// Read in all elements in the proper order. |
788 |
for (int i=0; i<elementData.length; i++) |
789 |
elementData[i] = (E) s.readObject(); |
790 |
array = elementData; |
791 |
} |
792 |
|
793 |
/** |
794 |
* Returns a string representation of this list, containing |
795 |
* the String representation of each element. |
796 |
*/ |
797 |
public String toString() { |
798 |
StringBuffer buf = new StringBuffer(); |
799 |
Iterator e = iterator(); |
800 |
buf.append("["); |
801 |
int maxIndex = size() - 1; |
802 |
for (int i = 0; i <= maxIndex; i++) { |
803 |
buf.append(String.valueOf(e.next())); |
804 |
if (i < maxIndex) |
805 |
buf.append(", "); |
806 |
} |
807 |
buf.append("]"); |
808 |
return buf.toString(); |
809 |
} |
810 |
|
811 |
/** |
812 |
* Compares the specified object with this list for equality. |
813 |
* Returns true if and only if the specified object is also a {@link |
814 |
* List}, both lists have the same size, and all corresponding pairs |
815 |
* of elements in the two lists are <em>equal</em>. (Two elements |
816 |
* <tt>e1</tt> and <tt>e2</tt> are <em>equal</em> if <tt>(e1==null ? |
817 |
* e2==null : e1.equals(e2))</tt>.) In other words, two lists are |
818 |
* defined to be equal if they contain the same elements in the same |
819 |
* order. |
820 |
* |
821 |
* @param o the object to be compared for equality with this list |
822 |
* @return <tt>true</tt> if the specified object is equal to this list |
823 |
*/ |
824 |
public boolean equals(Object o) { |
825 |
if (o == this) |
826 |
return true; |
827 |
if (!(o instanceof List)) |
828 |
return false; |
829 |
|
830 |
List<E> l2 = (List<E>)(o); |
831 |
if (size() != l2.size()) |
832 |
return false; |
833 |
|
834 |
ListIterator<E> e1 = listIterator(); |
835 |
ListIterator<E> e2 = l2.listIterator(); |
836 |
while (e1.hasNext()) { |
837 |
E o1 = e1.next(); |
838 |
E o2 = e2.next(); |
839 |
if (!(o1==null ? o2==null : o1.equals(o2))) |
840 |
return false; |
841 |
} |
842 |
return true; |
843 |
} |
844 |
|
845 |
/** |
846 |
* Returns the hash code value for this list. |
847 |
* |
848 |
* <p> This implementation uses the definition in {@link |
849 |
* List#hashCode}. |
850 |
* @return the hash code |
851 |
*/ |
852 |
public int hashCode() { |
853 |
int hashCode = 1; |
854 |
Iterator<E> i = iterator(); |
855 |
while (i.hasNext()) { |
856 |
E obj = i.next(); |
857 |
hashCode = 31*hashCode + (obj==null ? 0 : obj.hashCode()); |
858 |
} |
859 |
return hashCode; |
860 |
} |
861 |
|
862 |
/** |
863 |
* Returns an iterator over the elements in this list in proper sequence. |
864 |
* |
865 |
* <p>The returned iterator provides a snapshot of the state of the list |
866 |
* when the iterator was constructed. No synchronization is needed while |
867 |
* traversing the iterator. The iterator does <em>NOT</em> support the |
868 |
* <tt>remove</tt> method. |
869 |
* |
870 |
* @return an iterator over the elements in this list in proper sequence |
871 |
*/ |
872 |
public Iterator<E> iterator() { |
873 |
return new COWIterator<E>(array(), 0); |
874 |
} |
875 |
|
876 |
/** |
877 |
* {@inheritDoc} |
878 |
* |
879 |
* <p>The returned iterator provides a snapshot of the state of the list |
880 |
* when the iterator was constructed. No synchronization is needed while |
881 |
* traversing the iterator. The iterator does <em>NOT</em> support the |
882 |
* <tt>remove</tt>, <tt>set</tt> or <tt>add</tt> methods. |
883 |
*/ |
884 |
public ListIterator<E> listIterator() { |
885 |
return new COWIterator<E>(array(), 0); |
886 |
} |
887 |
|
888 |
/** |
889 |
* {@inheritDoc} |
890 |
* |
891 |
* <p>The list iterator returned by this implementation will throw an |
892 |
* <tt>UnsupportedOperationException</tt> in its <tt>remove</tt>, |
893 |
* <tt>set</tt> and <tt>add</tt> methods. |
894 |
* |
895 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
896 |
*/ |
897 |
public ListIterator<E> listIterator(final int index) { |
898 |
E[] elementData = array(); |
899 |
int len = elementData.length; |
900 |
if (index<0 || index>len) |
901 |
throw new IndexOutOfBoundsException("Index: "+index); |
902 |
|
903 |
return new COWIterator<E>(array(), index); |
904 |
} |
905 |
|
906 |
private static class COWIterator<E> implements ListIterator<E> { |
907 |
|
908 |
/** Snapshot of the array **/ |
909 |
private final E[] array; |
910 |
|
911 |
/** |
912 |
* Index of element to be returned by subsequent call to next. |
913 |
*/ |
914 |
private int cursor; |
915 |
|
916 |
private COWIterator(E[] elementArray, int initialCursor) { |
917 |
array = elementArray; |
918 |
cursor = initialCursor; |
919 |
} |
920 |
|
921 |
public boolean hasNext() { |
922 |
return cursor < array.length; |
923 |
} |
924 |
|
925 |
public boolean hasPrevious() { |
926 |
return cursor > 0; |
927 |
} |
928 |
|
929 |
public E next() { |
930 |
try { |
931 |
return array[cursor++]; |
932 |
} catch (IndexOutOfBoundsException ex) { |
933 |
throw new NoSuchElementException(); |
934 |
} |
935 |
} |
936 |
|
937 |
public E previous() { |
938 |
try { |
939 |
return array[--cursor]; |
940 |
} catch (IndexOutOfBoundsException e) { |
941 |
throw new NoSuchElementException(); |
942 |
} |
943 |
} |
944 |
|
945 |
public int nextIndex() { |
946 |
return cursor; |
947 |
} |
948 |
|
949 |
public int previousIndex() { |
950 |
return cursor-1; |
951 |
} |
952 |
|
953 |
/** |
954 |
* Not supported. Always throws UnsupportedOperationException. |
955 |
* @throws UnsupportedOperationException always; <tt>remove</tt> |
956 |
* is not supported by this iterator. |
957 |
*/ |
958 |
public void remove() { |
959 |
throw new UnsupportedOperationException(); |
960 |
} |
961 |
|
962 |
/** |
963 |
* Not supported. Always throws UnsupportedOperationException. |
964 |
* @throws UnsupportedOperationException always; <tt>set</tt> |
965 |
* is not supported by this iterator. |
966 |
*/ |
967 |
public void set(E e) { |
968 |
throw new UnsupportedOperationException(); |
969 |
} |
970 |
|
971 |
/** |
972 |
* Not supported. Always throws UnsupportedOperationException. |
973 |
* @throws UnsupportedOperationException always; <tt>add</tt> |
974 |
* is not supported by this iterator. |
975 |
*/ |
976 |
public void add(E e) { |
977 |
throw new UnsupportedOperationException(); |
978 |
} |
979 |
} |
980 |
|
981 |
/** |
982 |
* Returns a view of the portion of this list between <tt>fromIndex</tt>, |
983 |
* inclusive, and <tt>toIndex</tt>, exclusive. The returned list is |
984 |
* backed by this list, so changes in the returned list are reflected in |
985 |
* this list, and vice-versa. While mutative operations are supported, |
986 |
* they are probably not very useful for CopyOnWriteArrayLists. |
987 |
* |
988 |
* <p>The semantics of the list returned by this method become undefined if |
989 |
* the backing list (i.e., this list) is <i>structurally modified</i> in |
990 |
* any way other than via the returned list. (Structural modifications are |
991 |
* those that change the size of the list, or otherwise perturb it in such |
992 |
* a fashion that iterations in progress may yield incorrect results.) |
993 |
* |
994 |
* @param fromIndex low endpoint (inclusive) of the subList |
995 |
* @param toIndex high endpoint (exclusive) of the subList |
996 |
* @return a view of the specified range within this list |
997 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
998 |
*/ |
999 |
public synchronized List<E> subList(int fromIndex, int toIndex) { |
1000 |
// synchronized since sublist constructor depends on it. |
1001 |
int len = array.length; |
1002 |
if (fromIndex<0 || toIndex>len || fromIndex>toIndex) |
1003 |
throw new IndexOutOfBoundsException(); |
1004 |
return new COWSubList<E>(this, fromIndex, toIndex); |
1005 |
} |
1006 |
|
1007 |
private static class COWSubList<E> extends AbstractList<E> { |
1008 |
|
1009 |
/* |
1010 |
This class extends AbstractList merely for convenience, to |
1011 |
avoid having to define addAll, etc. This doesn't hurt, but |
1012 |
is wasteful. This class does not need or use modCount |
1013 |
mechanics in AbstractList, but does need to check for |
1014 |
concurrent modification using similar mechanics. On each |
1015 |
operation, the array that we expect the backing list to use |
1016 |
is checked and updated. Since we do this for all of the |
1017 |
base operations invoked by those defined in AbstractList, |
1018 |
all is well. While inefficient, this is not worth |
1019 |
improving. The kinds of list operations inherited from |
1020 |
AbstractList are already so slow on COW sublists that |
1021 |
adding a bit more space/time doesn't seem even noticeable. |
1022 |
*/ |
1023 |
|
1024 |
private final CopyOnWriteArrayList<E> l; |
1025 |
private final int offset; |
1026 |
private int size; |
1027 |
private E[] expectedArray; |
1028 |
|
1029 |
private COWSubList(CopyOnWriteArrayList<E> list, |
1030 |
int fromIndex, int toIndex) { |
1031 |
l = list; |
1032 |
expectedArray = l.array(); |
1033 |
offset = fromIndex; |
1034 |
size = toIndex - fromIndex; |
1035 |
} |
1036 |
|
1037 |
// only call this holding l's lock |
1038 |
private void checkForComodification() { |
1039 |
if (l.array != expectedArray) |
1040 |
throw new ConcurrentModificationException(); |
1041 |
} |
1042 |
|
1043 |
// only call this holding l's lock |
1044 |
private void rangeCheck(int index) { |
1045 |
if (index<0 || index>=size) |
1046 |
throw new IndexOutOfBoundsException("Index: "+index+ ",Size: "+size); |
1047 |
} |
1048 |
|
1049 |
|
1050 |
public E set(int index, E element) { |
1051 |
synchronized(l) { |
1052 |
rangeCheck(index); |
1053 |
checkForComodification(); |
1054 |
E x = l.set(index+offset, element); |
1055 |
expectedArray = l.array; |
1056 |
return x; |
1057 |
} |
1058 |
} |
1059 |
|
1060 |
public E get(int index) { |
1061 |
synchronized(l) { |
1062 |
rangeCheck(index); |
1063 |
checkForComodification(); |
1064 |
return l.get(index+offset); |
1065 |
} |
1066 |
} |
1067 |
|
1068 |
public int size() { |
1069 |
synchronized(l) { |
1070 |
checkForComodification(); |
1071 |
return size; |
1072 |
} |
1073 |
} |
1074 |
|
1075 |
public void add(int index, E element) { |
1076 |
synchronized(l) { |
1077 |
checkForComodification(); |
1078 |
if (index<0 || index>size) |
1079 |
throw new IndexOutOfBoundsException(); |
1080 |
l.add(index+offset, element); |
1081 |
expectedArray = l.array; |
1082 |
size++; |
1083 |
} |
1084 |
} |
1085 |
|
1086 |
public void clear() { |
1087 |
synchronized(l) { |
1088 |
checkForComodification(); |
1089 |
l.removeRange(offset, offset+size); |
1090 |
expectedArray = l.array; |
1091 |
size = 0; |
1092 |
} |
1093 |
} |
1094 |
|
1095 |
public E remove(int index) { |
1096 |
synchronized(l) { |
1097 |
rangeCheck(index); |
1098 |
checkForComodification(); |
1099 |
E result = l.remove(index+offset); |
1100 |
expectedArray = l.array; |
1101 |
size--; |
1102 |
return result; |
1103 |
} |
1104 |
} |
1105 |
|
1106 |
public Iterator<E> iterator() { |
1107 |
synchronized(l) { |
1108 |
checkForComodification(); |
1109 |
return new COWSubListIterator<E>(l, 0, offset, size); |
1110 |
} |
1111 |
} |
1112 |
|
1113 |
public ListIterator<E> listIterator(final int index) { |
1114 |
synchronized(l) { |
1115 |
checkForComodification(); |
1116 |
if (index<0 || index>size) |
1117 |
throw new IndexOutOfBoundsException("Index: "+index+", Size: "+size); |
1118 |
return new COWSubListIterator<E>(l, index, offset, size); |
1119 |
} |
1120 |
} |
1121 |
|
1122 |
public List<E> subList(int fromIndex, int toIndex) { |
1123 |
synchronized(l) { |
1124 |
checkForComodification(); |
1125 |
if (fromIndex<0 || toIndex>size) |
1126 |
throw new IndexOutOfBoundsException(); |
1127 |
return new COWSubList<E>(l, fromIndex+offset, toIndex+offset); |
1128 |
} |
1129 |
} |
1130 |
|
1131 |
} |
1132 |
|
1133 |
|
1134 |
private static class COWSubListIterator<E> implements ListIterator<E> { |
1135 |
private final ListIterator<E> i; |
1136 |
private final int index; |
1137 |
private final int offset; |
1138 |
private final int size; |
1139 |
private COWSubListIterator(List<E> l, int index, int offset, int size) { |
1140 |
this.index = index; |
1141 |
this.offset = offset; |
1142 |
this.size = size; |
1143 |
i = l.listIterator(index+offset); |
1144 |
} |
1145 |
|
1146 |
public boolean hasNext() { |
1147 |
return nextIndex() < size; |
1148 |
} |
1149 |
|
1150 |
public E next() { |
1151 |
if (hasNext()) |
1152 |
return i.next(); |
1153 |
else |
1154 |
throw new NoSuchElementException(); |
1155 |
} |
1156 |
|
1157 |
public boolean hasPrevious() { |
1158 |
return previousIndex() >= 0; |
1159 |
} |
1160 |
|
1161 |
public E previous() { |
1162 |
if (hasPrevious()) |
1163 |
return i.previous(); |
1164 |
else |
1165 |
throw new NoSuchElementException(); |
1166 |
} |
1167 |
|
1168 |
public int nextIndex() { |
1169 |
return i.nextIndex() - offset; |
1170 |
} |
1171 |
|
1172 |
public int previousIndex() { |
1173 |
return i.previousIndex() - offset; |
1174 |
} |
1175 |
|
1176 |
public void remove() { |
1177 |
throw new UnsupportedOperationException(); |
1178 |
} |
1179 |
|
1180 |
public void set(E e) { |
1181 |
throw new UnsupportedOperationException(); |
1182 |
} |
1183 |
|
1184 |
public void add(E e) { |
1185 |
throw new UnsupportedOperationException(); |
1186 |
} |
1187 |
} |
1188 |
|
1189 |
} |