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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.1 by tim, Wed May 14 21:30:45 2003 UTC vs.
Revision 1.45 by dl, Sun Oct 19 13:38:29 2003 UTC

#	Line 1 | Line 1
1	<	package java.util;
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	<	import java.util.*;
8	>	package java.util;
9
10		/**
11	<	* An unbounded (resizable) priority queue based on a priority
12	<	* heap.The take operation returns the least element with respect to
13	<	* the given ordering. (If more than one element is tied for least
14	<	* value, one of them is arbitrarily chosen to be returned -- no
15	<	* guarantees are made for ordering across ties.) Ordering follows the
16	<	* java.util.Collection conventions: Either the elements must be
17	<	* Comparable, or a Comparator must be supplied. Comparison failures
18	<	* throw ClassCastExceptions during insertions and extractions.
19	<	**/
20	<	public class PriorityQueue<E> extends AbstractCollection<E> implements Queue<E> {
21	<	public PriorityQueue(int initialCapacity) {}
22	<	public PriorityQueue(int initialCapacity, Comparator comparator) {}
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	>	* @param <E> the type of elements held in this collection
63	>	*/
64	>	public class PriorityQueue<E> extends AbstractQueue<E>
65	>	implements Queue<E>, java.io.Serializable {
66
67	<	public PriorityQueue(int initialCapacity, Collection initialElements) {}
67	>	private static final long serialVersionUID = -7720805057305804111L;
68
69	<	public PriorityQueue(int initialCapacity, Comparator comparator, Collection initialElements) {}
69	>	private static final int DEFAULT_INITIAL_CAPACITY = 11;
70
71	<	public boolean add(E x) {
72	<	return false;
71	>	/**
72	>	* Priority queue represented as a balanced binary heap: the two children
73	>	* of queue[n] are queue[2*n] and queue[2*n + 1].  The priority queue is
74	>	* ordered by comparator, or by the elements' natural ordering, if
75	>	* comparator is null:  For each node n in the heap and each descendant d
76	>	* of n, n <= d.
77	>	*
78	>	* The element with the lowest value is in queue[1], assuming the queue is
79	>	* nonempty.  (A one-based array is used in preference to the traditional
80	>	* zero-based array to simplify parent and child calculations.)
81	>	*
82	>	* queue.length must be >= 2, even if size == 0.
83	>	*/
84	>	private transient Object[] queue;
85	>
86	>	/**
87	>	* The number of elements in the priority queue.
88	>	*/
89	>	private int size = 0;
90	>
91	>	/**
92	>	* The comparator, or null if priority queue uses elements'
93	>	* natural ordering.
94	>	*/
95	>	private final Comparator<? super E> comparator;
96	>
97	>	/**
98	>	* The number of times this priority queue has been
99	>	* <i>structurally modified</i>.  See AbstractList for gory details.
100	>	*/
101	>	private transient int modCount = 0;
102	>
103	>	/**
104	>	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
105	>	* (11) that orders its elements according to their natural
106	>	* ordering (using <tt>Comparable</tt>).
107	>	*/
108	>	public PriorityQueue() {
109	>	this(DEFAULT_INITIAL_CAPACITY, null);
110		}
111	<	public boolean offer(E x) {
112	<	return false;
111	>
112	>	/**
113	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
114	>	* that orders its elements according to their natural ordering
115	>	* (using <tt>Comparable</tt>).
116	>	*
117	>	* @param initialCapacity the initial capacity for this priority queue.
118	>	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
119	>	* than 1
120	>	*/
121	>	public PriorityQueue(int initialCapacity) {
122	>	this(initialCapacity, null);
123		}
124	<	public boolean remove(Object x) {
125	<	return false;
124	>
125	>	/**
126	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
127	>	* that orders its elements according to the specified comparator.
128	>	*
129	>	* @param initialCapacity the initial capacity for this priority queue.
130	>	* @param comparator the comparator used to order this priority queue.
131	>	* If <tt>null</tt> then the order depends on the elements' natural
132	>	* ordering.
133	>	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
134	>	* than 1
135	>	*/
136	>	public PriorityQueue(int initialCapacity,
137	>	Comparator<? super E> comparator) {
138	>	if (initialCapacity < 1)
139	>	throw new IllegalArgumentException();
140	>	this.queue = new Object[initialCapacity + 1];
141	>	this.comparator = comparator;
142		}
143
144	<	public E remove() {
145	<	return null;
144	>	/**
145	>	* Common code to initialize underlying queue array across
146	>	* constructors below.
147	>	*/
148	>	private void initializeArray(Collection<? extends E> c) {
149	>	int sz = c.size();
150	>	int initialCapacity = (int)Math.min((sz * 110L) / 100,
151	>	Integer.MAX_VALUE - 1);
152	>	if (initialCapacity < 1)
153	>	initialCapacity = 1;
154	>
155	>	this.queue = new Object[initialCapacity + 1];
156		}
157	<	public Iterator<E> iterator() {
158	<	return null;
157	>
158	>	/**
159	>	* Initially fill elements of the queue array under the
160	>	* knowledge that it is sorted or is another PQ, in which
161	>	* case we can just place the elements in the order presented.
162	>	*/
163	>	private void fillFromSorted(Collection<? extends E> c) {
164	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
165	>	queue[++size] = i.next();
166		}
167
168	<	public E element() {
169	<	return null;
168	>	/**
169	>	* Initially fill elements of the queue array that is not to our knowledge
170	>	* sorted, so we must rearrange the elements to guarantee the heap
171	>	* invariant.
172	>	*/
173	>	private void fillFromUnsorted(Collection<? extends E> c) {
174	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
175	>	queue[++size] = i.next();
176	>	heapify();
177		}
178	<	public E poll() {
179	<	return null;
178	>
179	>	/**
180	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
181	>	* specified collection.  The priority queue has an initial
182	>	* capacity of 110% of the size of the specified collection or 1
183	>	* if the collection is empty.  If the specified collection is an
184	>	* instance of a {@link java.util.SortedSet} or is another
185	>	* <tt>PriorityQueue</tt>, the priority queue will be sorted
186	>	* according to the same comparator, or according to its elements'
187	>	* natural order if the collection is sorted according to its
188	>	* elements' natural order.  Otherwise, the priority queue is
189	>	* ordered according to its elements' natural order.
190	>	*
191	>	* @param c the collection whose elements are to be placed
192	>	*        into this priority queue.
193	>	* @throws ClassCastException if elements of the specified collection
194	>	*         cannot be compared to one another according to the priority
195	>	*         queue's ordering.
196	>	* @throws NullPointerException if <tt>c</tt> or any element within it
197	>	* is <tt>null</tt>
198	>	*/
199	>	public PriorityQueue(Collection<? extends E> c) {
200	>	initializeArray(c);
201	>	if (c instanceof SortedSet) {
202	>	// @fixme double-cast workaround for compiler
203	>	SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c;
204	>	comparator = (Comparator<? super E>)s.comparator();
205	>	fillFromSorted(s);
206	>	} else if (c instanceof PriorityQueue) {
207	>	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
208	>	comparator = (Comparator<? super E>)s.comparator();
209	>	fillFromSorted(s);
210	>	} else {
211	>	comparator = null;
212	>	fillFromUnsorted(c);
213	>	}
214	>	}
215	>
216	>	/**
217	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
218	>	* specified collection.  The priority queue has an initial
219	>	* capacity of 110% of the size of the specified collection or 1
220	>	* if the collection is empty.  This priority queue will be sorted
221	>	* according to the same comparator as the given collection, or
222	>	* according to its elements' natural order if the collection is
223	>	* sorted according to its elements' natural order.
224	>	*
225	>	* @param c the collection whose elements are to be placed
226	>	*        into this priority queue.
227	>	* @throws ClassCastException if elements of the specified collection
228	>	*         cannot be compared to one another according to the priority
229	>	*         queue's ordering.
230	>	* @throws NullPointerException if <tt>c</tt> or any element within it
231	>	* is <tt>null</tt>
232	>	*/
233	>	public PriorityQueue(PriorityQueue<? extends E> c) {
234	>	initializeArray(c);
235	>	comparator = (Comparator<? super E>)c.comparator();
236	>	fillFromSorted(c);
237	>	}
238	>
239	>	/**
240	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
241	>	* specified collection.  The priority queue has an initial
242	>	* capacity of 110% of the size of the specified collection or 1
243	>	* if the collection is empty.  This priority queue will be sorted
244	>	* according to the same comparator as the given collection, or
245	>	* according to its elements' natural order if the collection is
246	>	* sorted according to its elements' natural order.
247	>	*
248	>	* @param c the collection whose elements are to be placed
249	>	*        into this priority queue.
250	>	* @throws ClassCastException if elements of the specified collection
251	>	*         cannot be compared to one another according to the priority
252	>	*         queue's ordering.
253	>	* @throws NullPointerException if <tt>c</tt> or any element within it
254	>	* is <tt>null</tt>
255	>	*/
256	>	public PriorityQueue(SortedSet<? extends E> c) {
257	>	initializeArray(c);
258	>	comparator = (Comparator<? super E>)c.comparator();
259	>	fillFromSorted(c);
260	>	}
261	>
262	>	/**
263	>	* Resize array, if necessary, to be able to hold given index
264	>	*/
265	>	private void grow(int index) {
266	>	int newlen = queue.length;
267	>	if (index < newlen) // don't need to grow
268	>	return;
269	>	if (index == Integer.MAX_VALUE)
270	>	throw new OutOfMemoryError();
271	>	while (newlen <= index) {
272	>	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
273	>	newlen = Integer.MAX_VALUE;
274	>	else
275	>	newlen <<= 2;
276	>	}
277	>	Object[] newQueue = new Object[newlen];
278	>	System.arraycopy(queue, 0, newQueue, 0, queue.length);
279	>	queue = newQueue;
280		}
281	+
282	+
283	+	/**
284	+	* Inserts the specified element into this priority queue.
285	+	*
286	+	* @return <tt>true</tt>
287	+	* @throws ClassCastException if the specified element cannot be compared
288	+	* with elements currently in the priority queue according
289	+	* to the priority queue's ordering.
290	+	* @throws NullPointerException if the specified element is <tt>null</tt>.
291	+	*/
292	+	public boolean offer(E o) {
293	+	if (o == null)
294	+	throw new NullPointerException();
295	+	modCount++;
296	+	++size;
297	+
298	+	// Grow backing store if necessary
299	+	if (size >= queue.length)
300	+	grow(size);
301	+
302	+	queue[size] = o;
303	+	fixUp(size);
304	+	return true;
305	+	}
306	+
307		public E peek() {
308	<	return null;
308	>	if (size == 0)
309	>	return null;
310	>	return (E) queue[1];
311		}
312
313	<	public boolean isEmpty() {
313	>	// Collection Methods - the first two override to update docs
314	>
315	>	/**
316	>	* Adds the specified element to this queue.
317	>	* @return <tt>true</tt> (as per the general contract of
318	>	* <tt>Collection.add</tt>).
319	>	*
320	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
321	>	* @throws ClassCastException if the specified element cannot be compared
322	>	* with elements currently in the priority queue according
323	>	* to the priority queue's ordering.
324	>	*/
325	>	public boolean add(E o) {
326	>	return offer(o);
327	>	}
328	>
329	>	public boolean remove(Object o) {
330	>	if (o == null)
331	>	return false;
332	>
333	>	if (comparator == null) {
334	>	for (int i = 1; i <= size; i++) {
335	>	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
336	>	removeAt(i);
337	>	return true;
338	>	}
339	>	}
340	>	} else {
341	>	for (int i = 1; i <= size; i++) {
342	>	if (comparator.compare((E)queue[i], (E)o) == 0) {
343	>	removeAt(i);
344	>	return true;
345	>	}
346	>	}
347	>	}
348		return false;
349		}
350	+
351	+	/**
352	+	* Returns an iterator over the elements in this queue. The iterator
353	+	* does not return the elements in any particular order.
354	+	*
355	+	* @return an iterator over the elements in this queue.
356	+	*/
357	+	public Iterator<E> iterator() {
358	+	return new Itr();
359	+	}
360	+
361	+	private class Itr implements Iterator<E> {
362	+
363	+	/**
364	+	* Index (into queue array) of element to be returned by
365	+	* subsequent call to next.
366	+	*/
367	+	private int cursor = 1;
368	+
369	+	/**
370	+	* Index of element returned by most recent call to next,
371	+	* unless that element came from the forgetMeNot list.
372	+	* Reset to 0 if element is deleted by a call to remove.
373	+	*/
374	+	private int lastRet = 0;
375	+
376	+	/**
377	+	* The modCount value that the iterator believes that the backing
378	+	* List should have.  If this expectation is violated, the iterator
379	+	* has detected concurrent modification.
380	+	*/
381	+	private int expectedModCount = modCount;
382	+
383	+	/**
384	+	* A list of elements that were moved from the unvisited portion of
385	+	* the heap into the visited portion as a result of "unlucky" element
386	+	* removals during the iteration.  (Unlucky element removals are those
387	+	* that require a fixup instead of a fixdown.)  We must visit all of
388	+	* the elements in this list to complete the iteration.  We do this
389	+	* after we've completed the "normal" iteration.
390	+	*
391	+	* We expect that most iterations, even those involving removals,
392	+	* will not use need to store elements in this field.
393	+	*/
394	+	private ArrayList<E> forgetMeNot = null;
395	+
396	+	/**
397	+	* Element returned by the most recent call to next iff that
398	+	* element was drawn from the forgetMeNot list.
399	+	*/
400	+	private Object lastRetElt = null;
401	+
402	+	public boolean hasNext() {
403	+	return cursor <= size || forgetMeNot != null;
404	+	}
405	+
406	+	public E next() {
407	+	checkForComodification();
408	+	E result;
409	+	if (cursor <= size) {
410	+	result = (E) queue[cursor];
411	+	lastRet = cursor++;
412	+	}
413	+	else if (forgetMeNot == null)
414	+	throw new NoSuchElementException();
415	+	else {
416	+	int remaining = forgetMeNot.size();
417	+	result = forgetMeNot.remove(remaining - 1);
418	+	if (remaining == 1)
419	+	forgetMeNot = null;
420	+	lastRet = 0;
421	+	lastRetElt = result;
422	+	}
423	+	return result;
424	+	}
425	+
426	+	public void remove() {
427	+	checkForComodification();
428	+
429	+	if (lastRet != 0) {
430	+	E moved = PriorityQueue.this.removeAt(lastRet);
431	+	lastRet = 0;
432	+	if (moved == null) {
433	+	cursor--;
434	+	} else {
435	+	if (forgetMeNot == null)
436	+	forgetMeNot = new ArrayList<E>();
437	+	forgetMeNot.add(moved);
438	+	}
439	+	} else if (lastRetElt != null) {
440	+	PriorityQueue.this.remove(lastRetElt);
441	+	lastRetElt = null;
442	+	} else {
443	+	throw new IllegalStateException();
444	+	}
445	+
446	+	expectedModCount = modCount;
447	+	}
448	+
449	+	final void checkForComodification() {
450	+	if (modCount != expectedModCount)
451	+	throw new ConcurrentModificationException();
452	+	}
453	+	}
454	+
455		public int size() {
456	<	return 0;
456	>	return size;
457		}
458	<	public Object[] toArray() {
459	<	return null;
458	>
459	>	/**
460	>	* Remove all elements from the priority queue.
461	>	*/
462	>	public void clear() {
463	>	modCount++;
464	>
465	>	// Null out element references to prevent memory leak
466	>	for (int i=1; i<=size; i++)
467	>	queue[i] = null;
468	>
469	>	size = 0;
470		}
471
472	<	public <T> T[] toArray(T[] array) {
472	>	public E poll() {
473	>	if (size == 0)
474	>	return null;
475	>	modCount++;
476	>
477	>	E result = (E) queue[1];
478	>	queue[1] = queue[size];
479	>	queue[size--] = null;  // Drop extra ref to prevent memory leak
480	>	if (size > 1)
481	>	fixDown(1);
482	>
483	>	return result;
484	>	}
485	>
486	>	/**
487	>	* Removes and returns the ith element from queue.  (Recall that queue
488	>	* is one-based, so 1 <= i <= size.)
489	>	*
490	>	* Normally this method leaves the elements at positions from 1 up to i-1,
491	>	* inclusive, untouched.  Under these circumstances, it returns null.
492	>	* Occasionally, in order to maintain the heap invariant, it must move
493	>	* the last element of the list to some index in the range [2, i-1],
494	>	* and move the element previously at position (i/2) to position i.
495	>	* Under these circumstances, this method returns the element that was
496	>	* previously at the end of the list and is now at some position between
497	>	* 2 and i-1 inclusive.
498	>	*/
499	>	private E removeAt(int i) {
500	>	assert i > 0 && i <= size;
501	>	modCount++;
502	>
503	>	E moved = (E) queue[size];
504	>	queue[i] = moved;
505	>	queue[size--] = null;  // Drop extra ref to prevent memory leak
506	>	if (i <= size) {
507	>	fixDown(i);
508	>	if (queue[i] == moved) {
509	>	fixUp(i);
510	>	if (queue[i] != moved)
511	>	return moved;
512	>	}
513	>	}
514		return null;
515		}
516
517	+	/**
518	+	* Establishes the heap invariant (described above) assuming the heap
519	+	* satisfies the invariant except possibly for the leaf-node indexed by k
520	+	* (which may have a nextExecutionTime less than its parent's).
521	+	*
522	+	* This method functions by "promoting" queue[k] up the hierarchy
523	+	* (by swapping it with its parent) repeatedly until queue[k]
524	+	* is greater than or equal to its parent.
525	+	*/
526	+	private void fixUp(int k) {
527	+	if (comparator == null) {
528	+	while (k > 1) {
529	+	int j = k >> 1;
530	+	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
531	+	break;
532	+	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
533	+	k = j;
534	+	}
535	+	} else {
536	+	while (k > 1) {
537	+	int j = k >>> 1;
538	+	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
539	+	break;
540	+	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
541	+	k = j;
542	+	}
543	+	}
544	+	}
545	+
546	+	/**
547	+	* Establishes the heap invariant (described above) in the subtree
548	+	* rooted at k, which is assumed to satisfy the heap invariant except
549	+	* possibly for node k itself (which may be greater than its children).
550	+	*
551	+	* This method functions by "demoting" queue[k] down the hierarchy
552	+	* (by swapping it with its smaller child) repeatedly until queue[k]
553	+	* is less than or equal to its children.
554	+	*/
555	+	private void fixDown(int k) {
556	+	int j;
557	+	if (comparator == null) {
558	+	while ((j = k << 1) <= size && (j > 0)) {
559	+	if (j<size &&
560	+	((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
561	+	j++; // j indexes smallest kid
562	+
563	+	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
564	+	break;
565	+	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
566	+	k = j;
567	+	}
568	+	} else {
569	+	while ((j = k << 1) <= size && (j > 0)) {
570	+	if (j<size &&
571	+	comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
572	+	j++; // j indexes smallest kid
573	+	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
574	+	break;
575	+	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
576	+	k = j;
577	+	}
578	+	}
579	+	}
580	+
581	+	/**
582	+	* Establishes the heap invariant (described above) in the entire tree,
583	+	* assuming nothing about the order of the elements prior to the call.
584	+	*/
585	+	private void heapify() {
586	+	for (int i = size/2; i >= 1; i--)
587	+	fixDown(i);
588	+	}
589	+
590	+	/**
591	+	* Returns the comparator used to order this collection, or <tt>null</tt>
592	+	* if this collection is sorted according to its elements natural ordering
593	+	* (using <tt>Comparable</tt>).
594	+	*
595	+	* @return the comparator used to order this collection, or <tt>null</tt>
596	+	* if this collection is sorted according to its elements natural ordering.
597	+	*/
598	+	public Comparator<? super E> comparator() {
599	+	return comparator;
600	+	}
601	+
602	+	/**
603	+	* Save the state of the instance to a stream (that
604	+	* is, serialize it).
605	+	*
606	+	* @serialData The length of the array backing the instance is
607	+	* emitted (int), followed by all of its elements (each an
608	+	* <tt>Object</tt>) in the proper order.
609	+	* @param s the stream
610	+	*/
611	+	private void writeObject(java.io.ObjectOutputStream s)
612	+	throws java.io.IOException{
613	+	// Write out element count, and any hidden stuff
614	+	s.defaultWriteObject();
615	+
616	+	// Write out array length
617	+	s.writeInt(queue.length);
618	+
619	+	// Write out all elements in the proper order.
620	+	for (int i=1; i<=size; i++)
621	+	s.writeObject(queue[i]);
622	+	}
623	+
624	+	/**
625	+	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
626	+	* deserialize it).
627	+	* @param s the stream
628	+	*/
629	+	private void readObject(java.io.ObjectInputStream s)
630	+	throws java.io.IOException, ClassNotFoundException {
631	+	// Read in size, and any hidden stuff
632	+	s.defaultReadObject();
633	+
634	+	// Read in array length and allocate array
635	+	int arrayLength = s.readInt();
636	+	queue = new Object[arrayLength];
637	+
638	+	// Read in all elements in the proper order.
639	+	for (int i=1; i<=size; i++)
640	+	queue[i] = (E) s.readObject();
641	+	}
642	+
643		}

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