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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.4 by tim, Mon May 19 02:45:07 2003 UTC vs.
Revision 1.22 by dl, Tue Aug 5 12:11:08 2003 UTC

#	Line 1 | Line 1
1		package java.util;
2
3	–	/*
4	–	* Todo
5	–	*
6	–	*   1) Make it serializable.
7	–	*/
8	–
3		/**
4		* An unbounded priority queue based on a priority heap.  This queue orders
5	<	* elements according to the order specified at creation time.  This order is
6	<	* specified as for {@link TreeSet} and {@link TreeMap}: Elements are ordered
5	>	* elements according to an order specified at construction time, which is
6	>	* specified in the same manner as {@link java.util.TreeSet} and
7	>	* {@link java.util.TreeMap}: elements are ordered
8		* either according to their <i>natural order</i> (see {@link Comparable}), or
9	<	* according to a {@link Comparator}, depending on which constructor is used.
10	<	* The {@link #peek}, {@link #poll}, and {@link #remove} methods return the
11	<	* minimal element with respect to the specified ordering.  If multiple
12	<	* these elements are tied for least value, no guarantees are made as to
13	<	* which of elements is returned.
9	>	* according to a {@link java.util.Comparator}, depending on which
10	>	* constructor is used.
11	>	* <p>The <em>head</em> of this queue is the <em>least</em> element with
12	>	* respect to the specified ordering.
13	>	* If multiple elements are tied for least value, the
14	>	* head is one of those elements. A priority queue does not permit
15	>	* <tt>null</tt> elements.
16	>	*
17	>	* <p>The {@link #remove()} and {@link #poll()} methods remove and
18	>	* return the head of the queue.
19		*
20	<	* <p>Each priority queue has a <i>capacity</i>.  The capacity is the size of
21	<	* the array used to store the elements on the queue.  It is always at least
22	<	* as large as the queue size.  As elements are added to a priority list,
23	<	* its capacity grows automatically.  The details of the growth policy are not
24	<	* specified.
20	>	* <p>The {@link #element()} and {@link #peek()} methods return, but do
21	>	* not delete, the head of the queue.
22		*
23	<	*<p>Implementation note: this implementation provides O(log(n)) time for
24	<	* the <tt>offer</tt>, <tt>poll</tt>, <tt>remove()</tt> and <tt>add</tt>
25	<	* methods; linear time for the <tt>remove(Object)</tt> and
26	<	* <tt>contains</tt> methods; and constant time for the <tt>peek</tt>,
27	<	* <tt>element</tt>, and <tt>size</tt> methods.
23	>	* <p>A priority queue has a <i>capacity</i>.  The capacity is the
24	>	* size of the array used internally to store the elements on the
25	>	* queue.
26	>	* It is always at least as large as the queue size.  As
27	>	* elements are added to a priority queue, its capacity grows
28	>	* automatically.  The details of the growth policy are not specified.
29	>	*
30	>	* <p>Implementation note: this implementation provides O(log(n)) time
31	>	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
32	>	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
33	>	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
34	>	* constant time for the retrieval methods (<tt>peek</tt>,
35	>	* <tt>element</tt>, and <tt>size</tt>).
36		*
37		* <p>This class is a member of the
38		* <a href="{@docRoot}/../guide/collections/index.html">
39		* Java Collections Framework</a>.
40	+	* @since 1.5
41	+	* @author Josh Bloch
42		*/
43		public class PriorityQueue<E> extends AbstractQueue<E>
44	<	implements Queue<E>
45	<	{
44	>	implements Queue<E>, java.io.Serializable {
45	>
46		private static final int DEFAULT_INITIAL_CAPACITY = 11;
47
48		/**
49		* Priority queue represented as a balanced binary heap: the two children
50		* of queue[n] are queue[2*n] and queue[2*n + 1].  The priority queue is
51		* ordered by comparator, or by the elements' natural ordering, if
52	<	* comparator is null:  For each node n in the heap, and each descendant
53	<	* of n, d, n <= d.
52	>	* comparator is null:  For each node n in the heap and each descendant d
53	>	* of n, n <= d.
54		*
55	<	* The element with the lowest value is in queue[1] (assuming the queue is
56	<	* nonempty). A one-based array is used in preference to the traditional
57	<	* zero-based array to simplify parent and child calculations.
55	>	* The element with the lowest value is in queue[1], assuming the queue is
56	>	* nonempty.  (A one-based array is used in preference to the traditional
57	>	* zero-based array to simplify parent and child calculations.)
58		*
59		* queue.length must be >= 2, even if size == 0.
60		*/
61	<	private E[] queue;
61	>	private transient Object[] queue;
62
63		/**
64		* The number of elements in the priority queue.
#	Line 62 | Line 69 | public class PriorityQueue<E> extends Ab
69		* The comparator, or null if priority queue uses elements'
70		* natural ordering.
71		*/
72	<	private final Comparator<E> comparator;
72	>	private final Comparator<? super E> comparator;
73
74		/**
75		* The number of times this priority queue has been
76		* <i>structurally modified</i>.  See AbstractList for gory details.
77		*/
78	<	private int modCount = 0;
78	>	private transient int modCount = 0;
79
80		/**
81	<	* Create a new priority queue with the default initial capacity (11)
82	<	* that orders its elements according to their natural ordering.
81	>	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
82	>	* (11) that orders its elements according to their natural
83	>	* ordering (using <tt>Comparable</tt>.)
84		*/
85		public PriorityQueue() {
86	<	this(DEFAULT_INITIAL_CAPACITY);
86	>	this(DEFAULT_INITIAL_CAPACITY, null);
87		}
88
89		/**
90	<	* Create a new priority queue with the specified initial capacity
91	<	* that orders its elements according to their natural ordering.
90	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
91	>	* that orders its elements according to their natural ordering
92	>	* (using <tt>Comparable</tt>.)
93		*
94		* @param initialCapacity the initial capacity for this priority queue.
95		*/
#	Line 89 | Line 98 | public class PriorityQueue<E> extends Ab
98		}
99
100		/**
101	<	* Create a new priority queue with the specified initial capacity (11)
101	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
102		* that orders its elements according to the specified comparator.
103		*
104		* @param initialCapacity the initial capacity for this priority queue.
105		* @param comparator the comparator used to order this priority queue.
106	+	* If <tt>null</tt> then the order depends on the elements' natural
107	+	* ordering.
108	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
109	+	* than 1
110		*/
111	<	public PriorityQueue(int initialCapacity, Comparator<E> comparator) {
111	>	public PriorityQueue(int initialCapacity, Comparator<? super E> comparator) {
112		if (initialCapacity < 1)
113	<	initialCapacity = 1;
114	<	queue = new E[initialCapacity + 1];
113	>	throw new IllegalArgumentException();
114	>	this.queue = new Object[initialCapacity + 1];
115		this.comparator = comparator;
116		}
117
118		/**
119	<	* Create a new priority queue containing the elements in the specified
120	<	* collection.  The priority queue has an initial capacity of 110% of the
108	<	* size of the specified collection. If the specified collection
109	<	* implements the {@link Sorted} interface, the priority queue will be
110	<	* sorted according to the same comparator, or according to its elements'
111	<	* natural order if the collection is sorted according to its elements'
112	<	* natural order.  If the specified collection does not implement the
113	<	* <tt>Sorted</tt> interface, the priority queue is ordered according to
114	<	* its elements' natural order.
115	<	*
116	<	* @param initialElements the collection whose elements are to be placed
117	<	*        into this priority queue.
118	<	* @throws ClassCastException if elements of the specified collection
119	<	*         cannot be compared to one another according to the priority
120	<	*         queue's ordering.
121	<	* @throws NullPointerException if the specified collection or an
122	<	*         element of the specified collection is <tt>null</tt>.
119	>	* Common code to initialize underlying queue array across
120	>	* constructors below.
121		*/
122	<	public PriorityQueue(Collection<E> initialElements) {
123	<	int sz = initialElements.size();
122	>	private void initializeArray(Collection<? extends E> c) {
123	>	int sz = c.size();
124		int initialCapacity = (int)Math.min((sz * 110L) / 100,
125		Integer.MAX_VALUE - 1);
126		if (initialCapacity < 1)
127		initialCapacity = 1;
130	–	queue = new E[initialCapacity + 1];
128
129	<	if (initialElements instanceof Sorted) {
130	<	comparator = ((Sorted)initialElements).comparator();
131	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
132	<	queue[++size] = i.next();
133	<	} else {
129	>	this.queue = new Object[initialCapacity + 1];
130	>	}
131	>
132	>	/**
133	>	* Initially fill elements of the queue array under the
134	>	* knowledge that it is sorted or is another PQ, in which
135	>	* case we can just place the elements without fixups.
136	>	*/
137	>	private void fillFromSorted(Collection<? extends E> c) {
138	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
139	>	queue[++size] = i.next();
140	>	}
141	>
142	>
143	>	/**
144	>	* Initially fill elements of the queue array that is
145	>	* not to our knowledge sorted, so we must add them
146	>	* one by one.
147	>	*/
148	>	private void fillFromUnsorted(Collection<? extends E> c) {
149	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
150	>	add(i.next());
151	>	}
152	>
153	>	/**
154	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
155	>	* specified collection.  The priority queue has an initial
156	>	* capacity of 110% of the size of the specified collection or 1
157	>	* if the collection is empty.  If the specified collection is an
158	>	* instance of a {@link SortedSet} or is another
159	>	* <tt>PriorityQueue</tt>, the priority queue will be sorted
160	>	* according to the same comparator, or according to its elements'
161	>	* natural order if the collection is sorted according to its
162	>	* elements' natural order.  Otherwise, the priority queue is
163	>	* ordered according to its elements' natural order.
164	>	*
165	>	* @param c the collection whose elements are to be placed
166	>	*        into this priority queue.
167	>	* @throws ClassCastException if elements of the specified collection
168	>	*         cannot be compared to one another according to the priority
169	>	*         queue's ordering.
170	>	* @throws NullPointerException if <tt>c</tt> or any element within it
171	>	* is <tt>null</tt>
172	>	*/
173	>	public PriorityQueue(Collection<? extends E> c) {
174	>	initializeArray(c);
175	>	if (c instanceof SortedSet<? extends E>) {
176	>	SortedSet<? extends E> s = (SortedSet<? extends E>) c;
177	>	comparator = (Comparator<? super E>)s.comparator();
178	>	fillFromSorted(s);
179	>	}
180	>	else if (c instanceof PriorityQueue<? extends E>) {
181	>	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
182	>	comparator = (Comparator<? super E>)s.comparator();
183	>	fillFromSorted(s);
184	>	}
185	>	else {
186		comparator = null;
187	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
139	<	add(i.next());
187	>	fillFromUnsorted(c);
188		}
189		}
190
191	+	/**
192	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
193	+	* specified collection.  The priority queue has an initial
194	+	* capacity of 110% of the size of the specified collection or 1
195	+	* if the collection is empty.  This priority queue will be sorted
196	+	* according to the same comparator as the given collection, or
197	+	* according to its elements' natural order if the collection is
198	+	* sorted according to its elements' natural order.
199	+	*
200	+	* @param c the collection whose elements are to be placed
201	+	*        into this priority queue.
202	+	* @throws ClassCastException if elements of the specified collection
203	+	*         cannot be compared to one another according to the priority
204	+	*         queue's ordering.
205	+	* @throws NullPointerException if <tt>c</tt> or any element within it
206	+	* is <tt>null</tt>
207	+	*/
208	+	public PriorityQueue(PriorityQueue<? extends E> c) {
209	+	initializeArray(c);
210	+	comparator = (Comparator<? super E>)c.comparator();
211	+	fillFromSorted(c);
212	+	}
213	+
214	+	/**
215	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
216	+	* specified collection.  The priority queue has an initial
217	+	* capacity of 110% of the size of the specified collection or 1
218	+	* if the collection is empty.  This priority queue will be sorted
219	+	* according to the same comparator as the given collection, or
220	+	* according to its elements' natural order if the collection is
221	+	* sorted according to its elements' natural order.
222	+	*
223	+	* @param c the collection whose elements are to be placed
224	+	*        into this priority queue.
225	+	* @throws ClassCastException if elements of the specified collection
226	+	*         cannot be compared to one another according to the priority
227	+	*         queue's ordering.
228	+	* @throws NullPointerException if <tt>c</tt> or any element within it
229	+	* is <tt>null</tt>
230	+	*/
231	+	public PriorityQueue(SortedSet<? extends E> c) {
232	+	initializeArray(c);
233	+	comparator = (Comparator<? super E>)c.comparator();
234	+	fillFromSorted(c);
235	+	}
236	+
237	+	/**
238	+	* Resize array, if necessary, to be able to hold given index
239	+	*/
240	+	private void grow(int index) {
241	+	int newlen = queue.length;
242	+	if (index < newlen) // don't need to grow
243	+	return;
244	+	if (index == Integer.MAX_VALUE)
245	+	throw new OutOfMemoryError();
246	+	while (newlen <= index) {
247	+	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
248	+	newlen = Integer.MAX_VALUE;
249	+	else
250	+	newlen <<= 2;
251	+	}
252	+	Object[] newQueue = new Object[newlen];
253	+	System.arraycopy(queue, 0, newQueue, 0, queue.length);
254	+	queue = newQueue;
255	+	}
256	+
257		// Queue Methods
258
259		/**
260	<	* Remove and return the minimal element from this priority queue if
147	<	* it contains one or more elements, otherwise <tt>null</tt>.  The term
148	<	* <i>minimal</i> is defined according to this priority queue's order.
260	>	* Add the specified element to this priority queue.
261		*
262	<	* @return the minimal element from this priority queue if it contains
263	<	*         one or more elements, otherwise <tt>null</tt>.
262	>	* @return <tt>true</tt>
263	>	* @throws ClassCastException if the specified element cannot be compared
264	>	* with elements currently in the priority queue according
265	>	* to the priority queue's ordering.
266	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
267		*/
268	+	public boolean offer(E o) {
269	+	if (o == null)
270	+	throw new NullPointerException();
271	+	modCount++;
272	+	++size;
273	+
274	+	// Grow backing store if necessary
275	+	if (size >= queue.length)
276	+	grow(size);
277	+
278	+	queue[size] = o;
279	+	fixUp(size);
280	+	return true;
281	+	}
282	+
283		public E poll() {
284		if (size == 0)
285		return null;
286	<	return remove(1);
286	>	return (E) remove(1);
287		}
288
159	–	/**
160	–	* Return, but do not remove, the minimal element from the priority queue,
161	–	* or <tt>null</tt> if the queue is empty.  The term <i>minimal</i> is
162	–	* defined according to this priority queue's order.  This method returns
163	–	* the same object reference that would be returned by by the
164	–	* <tt>poll</tt> method.  The two methods differ in that this method
165	–	* does not remove the element from the priority queue.
166	–	*
167	–	* @return the minimal element from this priority queue if it contains
168	–	*         one or more elements, otherwise <tt>null</tt>.
169	–	*/
289		public E peek() {
290	<	return queue[1];
290	>	return (E) queue[1];
291		}
292
293		// Collection Methods
294
295	+	// these first two override just to get the throws docs
296	+
297		/**
298	<	* Removes a single instance of the specified element from this priority
178	<	* queue, if it is present.  Returns true if this collection contained the
179	<	* specified element (or equivalently, if this collection changed as a
180	<	* result of the call).
181	<	*
182	<	* @param o element to be removed from this collection, if present.
183	<	* @return <tt>true</tt> if this collection changed as a result of the
184	<	*         call
298	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
299		* @throws ClassCastException if the specified element cannot be compared
300	<	*            with elements currently in the priority queue according
301	<	*            to the priority queue's ordering.
188	<	* @throws NullPointerException if the specified element is null.
300	>	* with elements currently in the priority queue according
301	>	* to the priority queue's ordering.
302		*/
303	<	public boolean remove(Object element) {
304	<	if (element == null)
305	<	throw new NullPointerException();
303	>	public boolean add(E o) {
304	>	return super.add(o);
305	>	}
306	>
307	>	/**
308	>	* @throws ClassCastException if any element cannot be compared
309	>	* with elements currently in the priority queue according
310	>	* to the priority queue's ordering.
311	>	* @throws NullPointerException if <tt>c</tt> or any element in <tt>c</tt>
312	>	* is <tt>null</tt>
313	>	*/
314	>	public boolean addAll(Collection<? extends E> c) {
315	>	return super.addAll(c);
316	>	}
317	>
318	>	public boolean remove(Object o) {
319	>	if (o == null)
320	>	return false;
321
322		if (comparator == null) {
323		for (int i = 1; i <= size; i++) {
324	<	if (((Comparable)queue[i]).compareTo(element) == 0) {
324	>	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
325		remove(i);
326		return true;
327		}
328		}
329		} else {
330		for (int i = 1; i <= size; i++) {
331	<	if (comparator.compare(queue[i], (E) element) == 0) {
331	>	if (comparator.compare((E)queue[i], (E)o) == 0) {
332		remove(i);
333		return true;
334		}
#	Line 209 | Line 337 | public class PriorityQueue<E> extends Ab
337		return false;
338		}
339
212	–	/**
213	–	* Returns an iterator over the elements in this priority queue.  The
214	–	* first element returned by this iterator is the same element that
215	–	* would be returned by a call to <tt>peek</tt>.
216	–	*
217	–	* @return an <tt>Iterator</tt> over the elements in this priority queue.
218	–	*/
340		public Iterator<E> iterator() {
341		return new Itr();
342		}
#	Line 225 | Line 346 | public class PriorityQueue<E> extends Ab
346		* Index (into queue array) of element to be returned by
347		* subsequent call to next.
348		*/
349	<	int cursor = 1;
349	>	private int cursor = 1;
350
351		/**
352		* Index of element returned by most recent call to next or
353		* previous.  Reset to 0 if this element is deleted by a call
354		* to remove.
355		*/
356	<	int lastRet = 0;
356	>	private int lastRet = 0;
357
358		/**
359		* The modCount value that the iterator believes that the backing
360		* List should have.  If this expectation is violated, the iterator
361		* has detected concurrent modification.
362		*/
363	<	int expectedModCount = modCount;
363	>	private int expectedModCount = modCount;
364
365		public boolean hasNext() {
366		return cursor <= size;
#	Line 249 | Line 370 | public class PriorityQueue<E> extends Ab
370		checkForComodification();
371		if (cursor > size)
372		throw new NoSuchElementException();
373	<	E result = queue[cursor];
373	>	E result = (E) queue[cursor];
374		lastRet = cursor++;
375		return result;
376		}
#	Line 282 | Line 403 | public class PriorityQueue<E> extends Ab
403		}
404
405		/**
285	–	* Add the specified element to this priority queue.
286	–	*
287	–	* @param element the element to add.
288	–	* @return true
289	–	* @throws ClassCastException if the specified element cannot be compared
290	–	*            with elements currently in the priority queue according
291	–	*            to the priority queue's ordering.
292	–	* @throws NullPointerException if the specified element is null.
293	–	*/
294	–	public boolean offer(E element) {
295	–	if (element == null)
296	–	throw new NullPointerException();
297	–	modCount++;
298	–
299	–	// Grow backing store if necessary
300	–	if (++size == queue.length) {
301	–	E[] newQueue = new E[2 * queue.length];
302	–	System.arraycopy(queue, 0, newQueue, 0, size);
303	–	queue = newQueue;
304	–	}
305	–
306	–	queue[size] = element;
307	–	fixUp(size);
308	–	return true;
309	–	}
310	–
311	–	/**
406		* Remove all elements from the priority queue.
407		*/
408		public void clear() {
#	Line 332 | Line 426 | public class PriorityQueue<E> extends Ab
426		assert i <= size;
427		modCount++;
428
429	<	E result = queue[i];
429	>	E result = (E) queue[i];
430		queue[i] = queue[size];
431		queue[size--] = null;  // Drop extra ref to prevent memory leak
432		if (i <= size)
#	Line 353 | Line 447 | public class PriorityQueue<E> extends Ab
447		if (comparator == null) {
448		while (k > 1) {
449		int j = k >> 1;
450	<	if (((Comparable)queue[j]).compareTo(queue[k]) <= 0)
450	>	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
451		break;
452	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
452	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
453		k = j;
454		}
455		} else {
456		while (k > 1) {
457		int j = k >> 1;
458	<	if (comparator.compare(queue[j], queue[k]) <= 0)
458	>	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
459		break;
460	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
460	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
461		k = j;
462		}
463		}
#	Line 382 | Line 476 | public class PriorityQueue<E> extends Ab
476		int j;
477		if (comparator == null) {
478		while ((j = k << 1) <= size) {
479	<	if (j<size && ((Comparable)queue[j]).compareTo(queue[j+1]) > 0)
479	>	if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
480		j++; // j indexes smallest kid
481	<	if (((Comparable)queue[k]).compareTo(queue[j]) <= 0)
481	>	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
482		break;
483	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
483	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
484		k = j;
485		}
486		} else {
487		while ((j = k << 1) <= size) {
488	<	if (j < size && comparator.compare(queue[j], queue[j+1]) > 0)
488	>	if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
489		j++; // j indexes smallest kid
490	<	if (comparator.compare(queue[k], queue[j]) <= 0)
490	>	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
491		break;
492	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
492	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
493		k = j;
494		}
495		}
496		}
497
498	+	public Comparator<? super E> comparator() {
499	+	return comparator;
500	+	}
501	+
502		/**
503	<	* Returns the comparator associated with this priority queue, or
504	<	* <tt>null</tt> if it uses its elements' natural ordering.
503	>	* Save the state of the instance to a stream (that
504	>	* is, serialize it).
505		*
506	<	* @return the comparator associated with this priority queue, or
507	<	*         <tt>null</tt> if it uses its elements' natural ordering.
506	>	* @serialData The length of the array backing the instance is
507	>	* emitted (int), followed by all of its elements (each an
508	>	* <tt>Object</tt>) in the proper order.
509	>	* @param s the stream
510		*/
511	<	Comparator<E> comparator() {
512	<	return comparator;
511	>	private void writeObject(java.io.ObjectOutputStream s)
512	>	throws java.io.IOException{
513	>	// Write out element count, and any hidden stuff
514	>	s.defaultWriteObject();
515	>
516	>	// Write out array length
517	>	s.writeInt(queue.length);
518	>
519	>	// Write out all elements in the proper order.
520	>	for (int i=0; i<size; i++)
521	>	s.writeObject(queue[i]);
522		}
523	+
524	+	/**
525	+	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
526	+	* deserialize it).
527	+	* @param s the stream
528	+	*/
529	+	private void readObject(java.io.ObjectInputStream s)
530	+	throws java.io.IOException, ClassNotFoundException {
531	+	// Read in size, and any hidden stuff
532	+	s.defaultReadObject();
533	+
534	+	// Read in array length and allocate array
535	+	int arrayLength = s.readInt();
536	+	queue = new Object[arrayLength];
537	+
538	+	// Read in all elements in the proper order.
539	+	for (int i=0; i<size; i++)
540	+	queue[i] = s.readObject();
541	+	}
542	+
543		}
544	+

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