1 |
/* |
2 |
* %W% %E% |
3 |
* |
4 |
* Copyright 2003 Sun Microsystems, Inc. All rights reserved. |
5 |
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
6 |
*/ |
7 |
|
8 |
package java.util; |
9 |
|
10 |
/** |
11 |
* An unbounded priority {@linkplain Queue queue} based on a priority |
12 |
* heap. This queue orders elements according to an order specified |
13 |
* at construction time, which is specified either according to their |
14 |
* <i>natural order</i> (see {@link Comparable}), or according to a |
15 |
* {@link java.util.Comparator}, depending on which constructor is |
16 |
* used. A priority queue does not permit <tt>null</tt> elements. |
17 |
* A priority queue relying on natural ordering also does not |
18 |
* permit insertion of non-comparable objects (doing so may result |
19 |
* in <tt>ClassCastException</tt>). |
20 |
* |
21 |
* <p>The <em>head</em> of this queue is the <em>least</em> element |
22 |
* with respect to the specified ordering. If multiple elements are |
23 |
* tied for least value, the head is one of those elements -- ties are |
24 |
* broken arbitrarily. The queue retrieval operations <tt>poll</tt>, |
25 |
* <tt>remove</tt>, <tt>peek</tt>, and <tt>element</tt> access the |
26 |
* element at the head of the queue. |
27 |
* |
28 |
* <p>A priority queue is unbounded, but has an internal |
29 |
* <i>capacity</i> governing the size of an array used to store the |
30 |
* elements on the queue. It is always at least as large as the queue |
31 |
* size. As elements are added to a priority queue, its capacity |
32 |
* grows automatically. The details of the growth policy are not |
33 |
* specified. |
34 |
* |
35 |
* <p>This class implements all of the <em>optional</em> methods of |
36 |
* the {@link Collection} and {@link Iterator} interfaces. The |
37 |
* Iterator provided in method {@link #iterator()} is <em>not</em> |
38 |
* guaranteed to traverse the elements of the PriorityQueue in any |
39 |
* particular order. If you need ordered traversal, consider using |
40 |
* <tt>Arrays.sort(pq.toArray())</tt>. |
41 |
* |
42 |
* <p> <strong>Note that this implementation is not synchronized.</strong> |
43 |
* Multiple threads should not access a <tt>PriorityQueue</tt> |
44 |
* instance concurrently if any of the threads modifies the list |
45 |
* structurally. Instead, use the thread-safe {@link |
46 |
* java.util.concurrent.PriorityBlockingQueue} class. |
47 |
* |
48 |
* |
49 |
* <p>Implementation note: this implementation provides O(log(n)) time |
50 |
* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>, |
51 |
* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the |
52 |
* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and |
53 |
* constant time for the retrieval methods (<tt>peek</tt>, |
54 |
* <tt>element</tt>, and <tt>size</tt>). |
55 |
* |
56 |
* <p>This class is a member of the |
57 |
* <a href="{@docRoot}/../guide/collections/index.html"> |
58 |
* Java Collections Framework</a>. |
59 |
* @since 1.5 |
60 |
* @version %I%, %G% |
61 |
* @author Josh Bloch |
62 |
*/ |
63 |
public class PriorityQueue<E> extends AbstractQueue<E> |
64 |
implements Queue<E>, java.io.Serializable { |
65 |
|
66 |
private static final long serialVersionUID = -7720805057305804111L; |
67 |
|
68 |
private static final int DEFAULT_INITIAL_CAPACITY = 11; |
69 |
|
70 |
/** |
71 |
* Priority queue represented as a balanced binary heap: the two children |
72 |
* of queue[n] are queue[2*n] and queue[2*n + 1]. The priority queue is |
73 |
* ordered by comparator, or by the elements' natural ordering, if |
74 |
* comparator is null: For each node n in the heap and each descendant d |
75 |
* of n, n <= d. |
76 |
* |
77 |
* The element with the lowest value is in queue[1], assuming the queue is |
78 |
* nonempty. (A one-based array is used in preference to the traditional |
79 |
* zero-based array to simplify parent and child calculations.) |
80 |
* |
81 |
* queue.length must be >= 2, even if size == 0. |
82 |
*/ |
83 |
private transient Object[] queue; |
84 |
|
85 |
/** |
86 |
* The number of elements in the priority queue. |
87 |
*/ |
88 |
private int size = 0; |
89 |
|
90 |
/** |
91 |
* The comparator, or null if priority queue uses elements' |
92 |
* natural ordering. |
93 |
*/ |
94 |
private final Comparator<? super E> comparator; |
95 |
|
96 |
/** |
97 |
* The number of times this priority queue has been |
98 |
* <i>structurally modified</i>. See AbstractList for gory details. |
99 |
*/ |
100 |
private transient int modCount = 0; |
101 |
|
102 |
/** |
103 |
* Creates a <tt>PriorityQueue</tt> with the default initial capacity |
104 |
* (11) that orders its elements according to their natural |
105 |
* ordering (using <tt>Comparable</tt>). |
106 |
*/ |
107 |
public PriorityQueue() { |
108 |
this(DEFAULT_INITIAL_CAPACITY, null); |
109 |
} |
110 |
|
111 |
/** |
112 |
* Creates a <tt>PriorityQueue</tt> with the specified initial capacity |
113 |
* that orders its elements according to their natural ordering |
114 |
* (using <tt>Comparable</tt>). |
115 |
* |
116 |
* @param initialCapacity the initial capacity for this priority queue. |
117 |
* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less |
118 |
* than 1 |
119 |
*/ |
120 |
public PriorityQueue(int initialCapacity) { |
121 |
this(initialCapacity, null); |
122 |
} |
123 |
|
124 |
/** |
125 |
* Creates a <tt>PriorityQueue</tt> with the specified initial capacity |
126 |
* that orders its elements according to the specified comparator. |
127 |
* |
128 |
* @param initialCapacity the initial capacity for this priority queue. |
129 |
* @param comparator the comparator used to order this priority queue. |
130 |
* If <tt>null</tt> then the order depends on the elements' natural |
131 |
* ordering. |
132 |
* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less |
133 |
* than 1 |
134 |
*/ |
135 |
public PriorityQueue(int initialCapacity, |
136 |
Comparator<? super E> comparator) { |
137 |
if (initialCapacity < 1) |
138 |
throw new IllegalArgumentException(); |
139 |
this.queue = new Object[initialCapacity + 1]; |
140 |
this.comparator = comparator; |
141 |
} |
142 |
|
143 |
/** |
144 |
* Common code to initialize underlying queue array across |
145 |
* constructors below. |
146 |
*/ |
147 |
private void initializeArray(Collection<? extends E> c) { |
148 |
int sz = c.size(); |
149 |
int initialCapacity = (int)Math.min((sz * 110L) / 100, |
150 |
Integer.MAX_VALUE - 1); |
151 |
if (initialCapacity < 1) |
152 |
initialCapacity = 1; |
153 |
|
154 |
this.queue = new Object[initialCapacity + 1]; |
155 |
} |
156 |
|
157 |
/** |
158 |
* Initially fill elements of the queue array under the |
159 |
* knowledge that it is sorted or is another PQ, in which |
160 |
* case we can just place the elements in the order presented. |
161 |
*/ |
162 |
private void fillFromSorted(Collection<? extends E> c) { |
163 |
for (Iterator<? extends E> i = c.iterator(); i.hasNext(); ) |
164 |
queue[++size] = i.next(); |
165 |
} |
166 |
|
167 |
/** |
168 |
* Initially fill elements of the queue array that is not to our knowledge |
169 |
* sorted, so we must rearrange the elements to guarantee the heap |
170 |
* invariant. |
171 |
*/ |
172 |
private void fillFromUnsorted(Collection<? extends E> c) { |
173 |
for (Iterator<? extends E> i = c.iterator(); i.hasNext(); ) |
174 |
queue[++size] = i.next(); |
175 |
heapify(); |
176 |
} |
177 |
|
178 |
/** |
179 |
* Creates a <tt>PriorityQueue</tt> containing the elements in the |
180 |
* specified collection. The priority queue has an initial |
181 |
* capacity of 110% of the size of the specified collection or 1 |
182 |
* if the collection is empty. If the specified collection is an |
183 |
* instance of a {@link java.util.SortedSet} or is another |
184 |
* <tt>PriorityQueue</tt>, the priority queue will be sorted |
185 |
* according to the same comparator, or according to its elements' |
186 |
* natural order if the collection is sorted according to its |
187 |
* elements' natural order. Otherwise, the priority queue is |
188 |
* ordered according to its elements' natural order. |
189 |
* |
190 |
* @param c the collection whose elements are to be placed |
191 |
* into this priority queue. |
192 |
* @throws ClassCastException if elements of the specified collection |
193 |
* cannot be compared to one another according to the priority |
194 |
* queue's ordering. |
195 |
* @throws NullPointerException if <tt>c</tt> or any element within it |
196 |
* is <tt>null</tt> |
197 |
*/ |
198 |
public PriorityQueue(Collection<? extends E> c) { |
199 |
initializeArray(c); |
200 |
if (c instanceof SortedSet) { |
201 |
// @fixme double-cast workaround for compiler |
202 |
SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c; |
203 |
comparator = (Comparator<? super E>)s.comparator(); |
204 |
fillFromSorted(s); |
205 |
} else if (c instanceof PriorityQueue) { |
206 |
PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c; |
207 |
comparator = (Comparator<? super E>)s.comparator(); |
208 |
fillFromSorted(s); |
209 |
} else { |
210 |
comparator = null; |
211 |
fillFromUnsorted(c); |
212 |
} |
213 |
} |
214 |
|
215 |
/** |
216 |
* Creates a <tt>PriorityQueue</tt> containing the elements in the |
217 |
* specified collection. The priority queue has an initial |
218 |
* capacity of 110% of the size of the specified collection or 1 |
219 |
* if the collection is empty. This priority queue will be sorted |
220 |
* according to the same comparator as the given collection, or |
221 |
* according to its elements' natural order if the collection is |
222 |
* sorted according to its elements' natural order. |
223 |
* |
224 |
* @param c the collection whose elements are to be placed |
225 |
* into this priority queue. |
226 |
* @throws ClassCastException if elements of the specified collection |
227 |
* cannot be compared to one another according to the priority |
228 |
* queue's ordering. |
229 |
* @throws NullPointerException if <tt>c</tt> or any element within it |
230 |
* is <tt>null</tt> |
231 |
*/ |
232 |
public PriorityQueue(PriorityQueue<? extends E> c) { |
233 |
initializeArray(c); |
234 |
comparator = (Comparator<? super E>)c.comparator(); |
235 |
fillFromSorted(c); |
236 |
} |
237 |
|
238 |
/** |
239 |
* Creates a <tt>PriorityQueue</tt> containing the elements in the |
240 |
* specified collection. The priority queue has an initial |
241 |
* capacity of 110% of the size of the specified collection or 1 |
242 |
* if the collection is empty. This priority queue will be sorted |
243 |
* according to the same comparator as the given collection, or |
244 |
* according to its elements' natural order if the collection is |
245 |
* sorted according to its elements' natural order. |
246 |
* |
247 |
* @param c the collection whose elements are to be placed |
248 |
* into this priority queue. |
249 |
* @throws ClassCastException if elements of the specified collection |
250 |
* cannot be compared to one another according to the priority |
251 |
* queue's ordering. |
252 |
* @throws NullPointerException if <tt>c</tt> or any element within it |
253 |
* is <tt>null</tt> |
254 |
*/ |
255 |
public PriorityQueue(SortedSet<? extends E> c) { |
256 |
initializeArray(c); |
257 |
comparator = (Comparator<? super E>)c.comparator(); |
258 |
fillFromSorted(c); |
259 |
} |
260 |
|
261 |
/** |
262 |
* Resize array, if necessary, to be able to hold given index |
263 |
*/ |
264 |
private void grow(int index) { |
265 |
int newlen = queue.length; |
266 |
if (index < newlen) // don't need to grow |
267 |
return; |
268 |
if (index == Integer.MAX_VALUE) |
269 |
throw new OutOfMemoryError(); |
270 |
while (newlen <= index) { |
271 |
if (newlen >= Integer.MAX_VALUE / 2) // avoid overflow |
272 |
newlen = Integer.MAX_VALUE; |
273 |
else |
274 |
newlen <<= 2; |
275 |
} |
276 |
Object[] newQueue = new Object[newlen]; |
277 |
System.arraycopy(queue, 0, newQueue, 0, queue.length); |
278 |
queue = newQueue; |
279 |
} |
280 |
|
281 |
|
282 |
/** |
283 |
* Inserts the specified element into this priority queue. |
284 |
* |
285 |
* @return <tt>true</tt> |
286 |
* @throws ClassCastException if the specified element cannot be compared |
287 |
* with elements currently in the priority queue according |
288 |
* to the priority queue's ordering. |
289 |
* @throws NullPointerException if the specified element is <tt>null</tt>. |
290 |
*/ |
291 |
public boolean offer(E o) { |
292 |
if (o == null) |
293 |
throw new NullPointerException(); |
294 |
modCount++; |
295 |
++size; |
296 |
|
297 |
// Grow backing store if necessary |
298 |
if (size >= queue.length) |
299 |
grow(size); |
300 |
|
301 |
queue[size] = o; |
302 |
fixUp(size); |
303 |
return true; |
304 |
} |
305 |
|
306 |
public E peek() { |
307 |
if (size == 0) |
308 |
return null; |
309 |
return (E) queue[1]; |
310 |
} |
311 |
|
312 |
// Collection Methods - the first two override to update docs |
313 |
|
314 |
/** |
315 |
* Adds the specified element to this queue. |
316 |
* @return <tt>true</tt> (as per the general contract of |
317 |
* <tt>Collection.add</tt>). |
318 |
* |
319 |
* @throws NullPointerException if the specified element is <tt>null</tt>. |
320 |
* @throws ClassCastException if the specified element cannot be compared |
321 |
* with elements currently in the priority queue according |
322 |
* to the priority queue's ordering. |
323 |
*/ |
324 |
public boolean add(E o) { |
325 |
return offer(o); |
326 |
} |
327 |
|
328 |
public boolean remove(Object o) { |
329 |
if (o == null) |
330 |
return false; |
331 |
|
332 |
if (comparator == null) { |
333 |
for (int i = 1; i <= size; i++) { |
334 |
if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) { |
335 |
removeAt(i); |
336 |
return true; |
337 |
} |
338 |
} |
339 |
} else { |
340 |
for (int i = 1; i <= size; i++) { |
341 |
if (comparator.compare((E)queue[i], (E)o) == 0) { |
342 |
removeAt(i); |
343 |
return true; |
344 |
} |
345 |
} |
346 |
} |
347 |
return false; |
348 |
} |
349 |
|
350 |
/** |
351 |
* Returns an iterator over the elements in this queue. The iterator |
352 |
* does not return the elements in any particular order. |
353 |
* |
354 |
* @return an iterator over the elements in this queue. |
355 |
*/ |
356 |
public Iterator<E> iterator() { |
357 |
return new Itr(); |
358 |
} |
359 |
|
360 |
private class Itr implements Iterator<E> { |
361 |
|
362 |
/** |
363 |
* Index (into queue array) of element to be returned by |
364 |
* subsequent call to next. |
365 |
*/ |
366 |
private int cursor = 1; |
367 |
|
368 |
/** |
369 |
* Index of element returned by most recent call to next, |
370 |
* unless that element came from the forgetMeNot list. |
371 |
* Reset to 0 if element is deleted by a call to remove. |
372 |
*/ |
373 |
private int lastRet = 0; |
374 |
|
375 |
/** |
376 |
* The modCount value that the iterator believes that the backing |
377 |
* List should have. If this expectation is violated, the iterator |
378 |
* has detected concurrent modification. |
379 |
*/ |
380 |
private int expectedModCount = modCount; |
381 |
|
382 |
/** |
383 |
* A list of elements that were moved from the unvisited portion of |
384 |
* the heap into the visited portion as a result of "unlucky" element |
385 |
* removals during the iteration. (Unlucky element removals are those |
386 |
* that require a fixup instead of a fixdown.) We must visit all of |
387 |
* the elements in this list to complete the iteration. We do this |
388 |
* after we've completed the "normal" iteration. |
389 |
* |
390 |
* We expect that most iterations, even those involving removals, |
391 |
* will not use need to store elements in this field. |
392 |
*/ |
393 |
private ArrayList<E> forgetMeNot = null; |
394 |
|
395 |
/** |
396 |
* Element returned by the most recent call to next iff that |
397 |
* element was drawn from the forgetMeNot list. |
398 |
*/ |
399 |
private Object lastRetElt = null; |
400 |
|
401 |
public boolean hasNext() { |
402 |
return cursor <= size || forgetMeNot != null; |
403 |
} |
404 |
|
405 |
public E next() { |
406 |
checkForComodification(); |
407 |
E result; |
408 |
if (cursor <= size) { |
409 |
result = (E) queue[cursor]; |
410 |
lastRet = cursor++; |
411 |
} |
412 |
else if (forgetMeNot == null) |
413 |
throw new NoSuchElementException(); |
414 |
else { |
415 |
int remaining = forgetMeNot.size(); |
416 |
result = forgetMeNot.remove(remaining - 1); |
417 |
if (remaining == 1) |
418 |
forgetMeNot = null; |
419 |
lastRet = 0; |
420 |
lastRetElt = result; |
421 |
} |
422 |
return result; |
423 |
} |
424 |
|
425 |
public void remove() { |
426 |
checkForComodification(); |
427 |
|
428 |
if (lastRet != 0) { |
429 |
E moved = PriorityQueue.this.removeAt(lastRet); |
430 |
lastRet = 0; |
431 |
if (moved == null) { |
432 |
cursor--; |
433 |
} else { |
434 |
if (forgetMeNot == null) |
435 |
forgetMeNot = new ArrayList<E>(); |
436 |
forgetMeNot.add(moved); |
437 |
} |
438 |
} else if (lastRetElt != null) { |
439 |
PriorityQueue.this.remove(lastRetElt); |
440 |
lastRetElt = null; |
441 |
} else { |
442 |
throw new IllegalStateException(); |
443 |
} |
444 |
|
445 |
expectedModCount = modCount; |
446 |
} |
447 |
|
448 |
final void checkForComodification() { |
449 |
if (modCount != expectedModCount) |
450 |
throw new ConcurrentModificationException(); |
451 |
} |
452 |
} |
453 |
|
454 |
public int size() { |
455 |
return size; |
456 |
} |
457 |
|
458 |
/** |
459 |
* Remove all elements from the priority queue. |
460 |
*/ |
461 |
public void clear() { |
462 |
modCount++; |
463 |
|
464 |
// Null out element references to prevent memory leak |
465 |
for (int i=1; i<=size; i++) |
466 |
queue[i] = null; |
467 |
|
468 |
size = 0; |
469 |
} |
470 |
|
471 |
public E poll() { |
472 |
if (size == 0) |
473 |
return null; |
474 |
modCount++; |
475 |
|
476 |
E result = (E) queue[1]; |
477 |
queue[1] = queue[size]; |
478 |
queue[size--] = null; // Drop extra ref to prevent memory leak |
479 |
if (size > 1) |
480 |
fixDown(1); |
481 |
|
482 |
return result; |
483 |
} |
484 |
|
485 |
/** |
486 |
* Removes and returns the ith element from queue. (Recall that queue |
487 |
* is one-based, so 1 <= i <= size.) |
488 |
* |
489 |
* Normally this method leaves the elements at positions from 1 up to i-1, |
490 |
* inclusive, untouched. Under these circumstances, it returns null. |
491 |
* Occasionally, in order to maintain the heap invariant, it must move |
492 |
* the last element of the list to some index in the range [2, i-1], |
493 |
* and move the element previously at position (i/2) to position i. |
494 |
* Under these circumstances, this method returns the element that was |
495 |
* previously at the end of the list and is now at some position between |
496 |
* 2 and i-1 inclusive. |
497 |
*/ |
498 |
private E removeAt(int i) { |
499 |
assert i > 0 && i <= size; |
500 |
modCount++; |
501 |
|
502 |
E moved = (E) queue[size]; |
503 |
queue[i] = moved; |
504 |
queue[size--] = null; // Drop extra ref to prevent memory leak |
505 |
if (i <= size) { |
506 |
fixDown(i); |
507 |
if (queue[i] == moved) { |
508 |
fixUp(i); |
509 |
if (queue[i] != moved) |
510 |
return moved; |
511 |
} |
512 |
} |
513 |
return null; |
514 |
} |
515 |
|
516 |
/** |
517 |
* Establishes the heap invariant (described above) assuming the heap |
518 |
* satisfies the invariant except possibly for the leaf-node indexed by k |
519 |
* (which may have a nextExecutionTime less than its parent's). |
520 |
* |
521 |
* This method functions by "promoting" queue[k] up the hierarchy |
522 |
* (by swapping it with its parent) repeatedly until queue[k] |
523 |
* is greater than or equal to its parent. |
524 |
*/ |
525 |
private void fixUp(int k) { |
526 |
if (comparator == null) { |
527 |
while (k > 1) { |
528 |
int j = k >> 1; |
529 |
if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0) |
530 |
break; |
531 |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
532 |
k = j; |
533 |
} |
534 |
} else { |
535 |
while (k > 1) { |
536 |
int j = k >>> 1; |
537 |
if (comparator.compare((E)queue[j], (E)queue[k]) <= 0) |
538 |
break; |
539 |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
540 |
k = j; |
541 |
} |
542 |
} |
543 |
} |
544 |
|
545 |
/** |
546 |
* Establishes the heap invariant (described above) in the subtree |
547 |
* rooted at k, which is assumed to satisfy the heap invariant except |
548 |
* possibly for node k itself (which may be greater than its children). |
549 |
* |
550 |
* This method functions by "demoting" queue[k] down the hierarchy |
551 |
* (by swapping it with its smaller child) repeatedly until queue[k] |
552 |
* is less than or equal to its children. |
553 |
*/ |
554 |
private void fixDown(int k) { |
555 |
int j; |
556 |
if (comparator == null) { |
557 |
while ((j = k << 1) <= size && (j > 0)) { |
558 |
if (j<size && |
559 |
((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0) |
560 |
j++; // j indexes smallest kid |
561 |
|
562 |
if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0) |
563 |
break; |
564 |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
565 |
k = j; |
566 |
} |
567 |
} else { |
568 |
while ((j = k << 1) <= size && (j > 0)) { |
569 |
if (j<size && |
570 |
comparator.compare((E)queue[j], (E)queue[j+1]) > 0) |
571 |
j++; // j indexes smallest kid |
572 |
if (comparator.compare((E)queue[k], (E)queue[j]) <= 0) |
573 |
break; |
574 |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
575 |
k = j; |
576 |
} |
577 |
} |
578 |
} |
579 |
|
580 |
/** |
581 |
* Establishes the heap invariant (described above) in the entire tree, |
582 |
* assuming nothing about the order of the elements prior to the call. |
583 |
*/ |
584 |
private void heapify() { |
585 |
for (int i = size/2; i >= 1; i--) |
586 |
fixDown(i); |
587 |
} |
588 |
|
589 |
/** |
590 |
* Returns the comparator used to order this collection, or <tt>null</tt> |
591 |
* if this collection is sorted according to its elements natural ordering |
592 |
* (using <tt>Comparable</tt>). |
593 |
* |
594 |
* @return the comparator used to order this collection, or <tt>null</tt> |
595 |
* if this collection is sorted according to its elements natural ordering. |
596 |
*/ |
597 |
public Comparator<? super E> comparator() { |
598 |
return comparator; |
599 |
} |
600 |
|
601 |
/** |
602 |
* Save the state of the instance to a stream (that |
603 |
* is, serialize it). |
604 |
* |
605 |
* @serialData The length of the array backing the instance is |
606 |
* emitted (int), followed by all of its elements (each an |
607 |
* <tt>Object</tt>) in the proper order. |
608 |
* @param s the stream |
609 |
*/ |
610 |
private void writeObject(java.io.ObjectOutputStream s) |
611 |
throws java.io.IOException{ |
612 |
// Write out element count, and any hidden stuff |
613 |
s.defaultWriteObject(); |
614 |
|
615 |
// Write out array length |
616 |
s.writeInt(queue.length); |
617 |
|
618 |
// Write out all elements in the proper order. |
619 |
for (int i=1; i<=size; i++) |
620 |
s.writeObject(queue[i]); |
621 |
} |
622 |
|
623 |
/** |
624 |
* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is, |
625 |
* deserialize it). |
626 |
* @param s the stream |
627 |
*/ |
628 |
private void readObject(java.io.ObjectInputStream s) |
629 |
throws java.io.IOException, ClassNotFoundException { |
630 |
// Read in size, and any hidden stuff |
631 |
s.defaultReadObject(); |
632 |
|
633 |
// Read in array length and allocate array |
634 |
int arrayLength = s.readInt(); |
635 |
queue = new Object[arrayLength]; |
636 |
|
637 |
// Read in all elements in the proper order. |
638 |
for (int i=1; i<=size; i++) |
639 |
queue[i] = (E) s.readObject(); |
640 |
} |
641 |
|
642 |
} |