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revision 1.61, Tue Feb 7 20:54:24 2006 UTC revision 1.73, Tue Jun 21 19:29:21 2011 UTC
# Line 1  Line 1 
1  /*  /*
2   * %W% %E%   * Copyright (c) 2003, 2006, Oracle and/or its affiliates. All rights reserved.
3     * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4   *   *
5   * Copyright 2006 Sun Microsystems, Inc. All rights reserved.   * This code is free software; you can redistribute it and/or modify it
6   * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.   * under the terms of the GNU General Public License version 2 only, as
7     * published by the Free Software Foundation.  Sun designates this
8     * particular file as subject to the "Classpath" exception as provided
9     * by Sun in the LICENSE file that accompanied this code.
10     *
11     * This code is distributed in the hope that it will be useful, but WITHOUT
12     * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13     * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14     * version 2 for more details (a copy is included in the LICENSE file that
15     * accompanied this code).
16     *
17     * You should have received a copy of the GNU General Public License version
18     * 2 along with this work; if not, write to the Free Software Foundation,
19     * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20     *
21     * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22     * or visit www.oracle.com if you need additional information or have any
23     * questions.
24   */   */
25    
26  package java.util;  package java.util;
27    
28  /**  /**
29   * An unbounded priority {@linkplain Queue queue} based on a priority   * An unbounded priority {@linkplain Queue queue} based on a priority heap.
30   * heap.  The elements of the priority queue are ordered according to   * The elements of the priority queue are ordered according to their
31   * their {@linkplain Comparable natural ordering}, or by a {@link   * {@linkplain Comparable natural ordering}, or by a {@link Comparator}
32   * Comparator} provided at queue construction time, depending on which   * provided at queue construction time, depending on which constructor is
33   * constructor is used.  A priority queue does not permit   * used.  A priority queue does not permit {@code null} elements.
34   * <tt>null</tt> elements.  A priority queue relying on natural   * A priority queue relying on natural ordering also does not permit
35   * ordering also does not permit insertion of non-comparable objects   * insertion of non-comparable objects (doing so may result in
36   * (doing so may result in <tt>ClassCastException</tt>).   * {@code ClassCastException}).
37   *   *
38   * <p>The <em>head</em> of this queue is the <em>least</em> element   * <p>The <em>head</em> of this queue is the <em>least</em> element
39   * with respect to the specified ordering.  If multiple elements are   * with respect to the specified ordering.  If multiple elements are
40   * tied for least value, the head is one of those elements -- ties are   * tied for least value, the head is one of those elements -- ties are
41   * broken arbitrarily.  The queue retrieval operations <tt>poll</tt>,   * broken arbitrarily.  The queue retrieval operations {@code poll},
42   * <tt>remove</tt>, <tt>peek</tt>, and <tt>element</tt> access the   * {@code remove}, {@code peek}, and {@code element} access the
43   * element at the head of the queue.   * element at the head of the queue.
44   *   *
45   * <p>A priority queue is unbounded, but has an internal   * <p>A priority queue is unbounded, but has an internal
# Line 36  Line 54 
54   * Iterator} interfaces.  The Iterator provided in method {@link   * Iterator} interfaces.  The Iterator provided in method {@link
55   * #iterator()} is <em>not</em> guaranteed to traverse the elements of   * #iterator()} is <em>not</em> guaranteed to traverse the elements of
56   * the priority queue in any particular order. If you need ordered   * the priority queue in any particular order. If you need ordered
57   * traversal, consider using <tt>Arrays.sort(pq.toArray())</tt>.   * traversal, consider using {@code Arrays.sort(pq.toArray())}.
58   *   *
59   * <p> <strong>Note that this implementation is not synchronized.</strong>   * <p> <strong>Note that this implementation is not synchronized.</strong>
60   * Multiple threads should not access a <tt>PriorityQueue</tt>   * Multiple threads should not access a {@code PriorityQueue}
61   * instance concurrently if any of the threads modifies the list   * instance concurrently if any of the threads modifies the queue.
62   * structurally. Instead, use the thread-safe {@link   * Instead, use the thread-safe {@link
63   * java.util.concurrent.PriorityBlockingQueue} class.   * java.util.concurrent.PriorityBlockingQueue} class.
64   *   *
65   * <p>Implementation note: this implementation provides O(log(n)) time   * <p>Implementation note: this implementation provides
66   * for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,   * O(log(n)) time for the enqueing and dequeing methods
67   * <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the   * ({@code offer}, {@code poll}, {@code remove()} and {@code add});
68   * <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and   * linear time for the {@code remove(Object)} and {@code contains(Object)}
69   * constant time for the retrieval methods (<tt>peek</tt>,   * methods; and constant time for the retrieval methods
70   * <tt>element</tt>, and <tt>size</tt>).   * ({@code peek}, {@code element}, and {@code size}).
71   *   *
72   * <p>This class is a member of the   * <p>This class is a member of the
73   * <a href="{@docRoot}/../guide/collections/index.html">   * <a href="{@docRoot}/../technotes/guides/collections/index.html">
74   * Java Collections Framework</a>.   * Java Collections Framework</a>.
75     *
76   * @since 1.5   * @since 1.5
77   * @version 1.8, 08/27/05   * @author Josh Bloch, Doug Lea
  * @author Josh Bloch  
78   * @param <E> the type of elements held in this collection   * @param <E> the type of elements held in this collection
79   */   */
80  public class PriorityQueue<E> extends AbstractQueue<E>  public class PriorityQueue<E> extends AbstractQueue<E>
# Line 94  Line 112 
112      private transient int modCount = 0;      private transient int modCount = 0;
113    
114      /**      /**
115       * Creates a <tt>PriorityQueue</tt> with the default initial       * Creates a {@code PriorityQueue} with the default initial
116       * capacity (11) that orders its elements according to their       * capacity (11) that orders its elements according to their
117       * {@linkplain Comparable natural ordering}.       * {@linkplain Comparable natural ordering}.
118       */       */
# Line 103  Line 121 
121      }      }
122    
123      /**      /**
124       * Creates a <tt>PriorityQueue</tt> with the specified initial       * Creates a {@code PriorityQueue} with the specified initial
125       * capacity that orders its elements according to their       * capacity that orders its elements according to their
126       * {@linkplain Comparable natural ordering}.       * {@linkplain Comparable natural ordering}.
127       *       *
128       * @param initialCapacity the initial capacity for this priority queue       * @param initialCapacity the initial capacity for this priority queue
129       * @throws IllegalArgumentException if <tt>initialCapacity</tt> is less       * @throws IllegalArgumentException if {@code initialCapacity} is less
130       * than 1       * than 1
131       */       */
132      public PriorityQueue(int initialCapacity) {      public PriorityQueue(int initialCapacity) {
# Line 116  Line 134 
134      }      }
135    
136      /**      /**
137       * Creates a <tt>PriorityQueue</tt> with the specified initial capacity       * Creates a {@code PriorityQueue} with the specified initial capacity
138       * that orders its elements according to the specified comparator.       * that orders its elements according to the specified comparator.
139       *       *
140       * @param  initialCapacity the initial capacity for this priority queue       * @param  initialCapacity the initial capacity for this priority queue
141       * @param  comparator the comparator that will be used to order       * @param  comparator the comparator that will be used to order this
142       *         this priority queue.  If <tt>null</tt>, the <i>natural       *         priority queue.  If {@code null}, the {@linkplain Comparable
143       *         ordering</i> of the elements will be used.       *         natural ordering} of the elements will be used.
144       * @throws IllegalArgumentException if <tt>initialCapacity</tt> is       * @throws IllegalArgumentException if {@code initialCapacity} is
145       *         less than 1       *         less than 1
146       */       */
147      public PriorityQueue(int initialCapacity,      public PriorityQueue(int initialCapacity,
# Line 137  Line 155 
155      }      }
156    
157      /**      /**
158       * Creates a <tt>PriorityQueue</tt> containing the elements in the       * Creates a {@code PriorityQueue} containing the elements in the
159       * specified collection.   If the specified collection is an       * specified collection.  If the specified collection is an instance of
160       * instance of a {@link java.util.SortedSet} or is another       * a {@link SortedSet} or is another {@code PriorityQueue}, this
161       * <tt>PriorityQueue</tt>, the priority queue will be ordered       * priority queue will be ordered according to the same ordering.
162       * according to the same ordering.  Otherwise, this priority queue       * Otherwise, this priority queue will be ordered according to the
163       * will be ordered according to the natural ordering of its elements.       * {@linkplain Comparable natural ordering} of its elements.
164       *       *
165       * @param  c the collection whose elements are to be placed       * @param  c the collection whose elements are to be placed
166       *         into this priority queue       *         into this priority queue
# Line 152  Line 170 
170       * @throws NullPointerException if the specified collection or any       * @throws NullPointerException if the specified collection or any
171       *         of its elements are null       *         of its elements are null
172       */       */
173        @SuppressWarnings("unchecked")
174      public PriorityQueue(Collection<? extends E> c) {      public PriorityQueue(Collection<? extends E> c) {
175          initFromCollection(c);          if (c instanceof SortedSet<?>) {
176          if (c instanceof SortedSet)              SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
177              comparator = (Comparator<? super E>)              this.comparator = (Comparator<? super E>) ss.comparator();
178                  ((SortedSet<? extends E>)c).comparator();              initElementsFromCollection(ss);
179          else if (c instanceof PriorityQueue)          }
180              comparator = (Comparator<? super E>)          else if (c instanceof PriorityQueue<?>) {
181                  ((PriorityQueue<? extends E>)c).comparator();              PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
182                this.comparator = (Comparator<? super E>) pq.comparator();
183                initFromPriorityQueue(pq);
184            }
185          else {          else {
186              comparator = null;              this.comparator = null;
187              heapify();              initFromCollection(c);
188          }          }
189      }      }
190    
191      /**      /**
192       * Creates a <tt>PriorityQueue</tt> containing the elements in the       * Creates a {@code PriorityQueue} containing the elements in the
193       * specified priority queue.  This priority queue will be       * specified priority queue.  This priority queue will be
194       * ordered according to the same ordering as the given priority       * ordered according to the same ordering as the given priority
195       * queue.       * queue.
196       *       *
197       * @param  c the priority queue whose elements are to be placed       * @param  c the priority queue whose elements are to be placed
198       *         into this priority queue       *         into this priority queue
199       * @throws ClassCastException if elements of <tt>c</tt> cannot be       * @throws ClassCastException if elements of {@code c} cannot be
200       *         compared to one another according to <tt>c</tt>'s       *         compared to one another according to {@code c}'s
201       *         ordering       *         ordering
202       * @throws NullPointerException if the specified priority queue or any       * @throws NullPointerException if the specified priority queue or any
203       *         of its elements are null       *         of its elements are null
204       */       */
205        @SuppressWarnings("unchecked")
206      public PriorityQueue(PriorityQueue<? extends E> c) {      public PriorityQueue(PriorityQueue<? extends E> c) {
207          comparator = (Comparator<? super E>)c.comparator();          this.comparator = (Comparator<? super E>) c.comparator();
208          initFromCollection(c);          initFromPriorityQueue(c);
209      }      }
210    
211      /**      /**
212       * Creates a <tt>PriorityQueue</tt> containing the elements in the       * Creates a {@code PriorityQueue} containing the elements in the
213       * specified sorted set.  This priority queue will be ordered       * specified sorted set.  This priority queue will be ordered
214       * according to the same ordering as the given sorted set.       * according to the same ordering as the given sorted set.
215       *       *
216       * @param  c the sorted set whose elements are to be placed       * @param  c the sorted set whose elements are to be placed
217       *         into this priority queue.       *         into this priority queue
218       * @throws ClassCastException if elements of the specified sorted       * @throws ClassCastException if elements of the specified sorted
219       *         set cannot be compared to one another according to the       *         set cannot be compared to one another according to the
220       *         sorted set's ordering       *         sorted set's ordering
221       * @throws NullPointerException if the specified sorted set or any       * @throws NullPointerException if the specified sorted set or any
222       *         of its elements are null       *         of its elements are null
223       */       */
224        @SuppressWarnings("unchecked")
225      public PriorityQueue(SortedSet<? extends E> c) {      public PriorityQueue(SortedSet<? extends E> c) {
226          comparator = (Comparator<? super E>)c.comparator();          this.comparator = (Comparator<? super E>) c.comparator();
227            initElementsFromCollection(c);
228        }
229    
230        private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
231            if (c.getClass() == PriorityQueue.class) {
232                this.queue = c.toArray();
233                this.size = c.size();
234            } else {
235          initFromCollection(c);          initFromCollection(c);
236      }      }
237        }
238    
239      /**      private void initElementsFromCollection(Collection<? extends E> c) {
      * Initialize queue array with elements from the given Collection.  
      * @param c the collection  
      */  
     private void initFromCollection(Collection<? extends E> c) {  
240          Object[] a = c.toArray();          Object[] a = c.toArray();
241          // If c.toArray incorrectly doesn't return Object[], copy it.          // If c.toArray incorrectly doesn't return Object[], copy it.
242          if (a.getClass() != Object[].class)          if (a.getClass() != Object[].class)
243              a = Arrays.copyOf(a, a.length, Object[].class);              a = Arrays.copyOf(a, a.length, Object[].class);
244          queue = a;          int len = a.length;
245          size = a.length;          if (len == 1 || this.comparator != null)
246                for (int i = 0; i < len; i++)
247                    if (a[i] == null)
248                        throw new NullPointerException();
249            this.queue = a;
250            this.size = a.length;
251      }      }
252    
253      /**      /**
254         * Initializes queue array with elements from the given Collection.
255         *
256         * @param c the collection
257         */
258        private void initFromCollection(Collection<? extends E> c) {
259            initElementsFromCollection(c);
260            heapify();
261        }
262    
263        /**
264         * The maximum size of array to allocate.
265         * Some VMs reserve some header words in an array.
266         * Attempts to allocate larger arrays may result in
267         * OutOfMemoryError: Requested array size exceeds VM limit
268         */
269        private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
270    
271        /**
272       * Increases the capacity of the array.       * Increases the capacity of the array.
273       *       *
274       * @param minCapacity the desired minimum capacity       * @param minCapacity the desired minimum capacity
275       */       */
276      private void grow(int minCapacity) {      private void grow(int minCapacity) {
         if (minCapacity < 0) // overflow  
             throw new OutOfMemoryError();  
277          int oldCapacity = queue.length;          int oldCapacity = queue.length;
278          // Double size if small; else grow by 50%          // Double size if small; else grow by 50%
279          int newCapacity = ((oldCapacity < 64)?          int newCapacity = oldCapacity + ((oldCapacity < 64) ?
280                             ((oldCapacity + 1) * 2):                                           (oldCapacity + 2) :
281                             ((oldCapacity / 2) * 3));                                           (oldCapacity >> 1));
282          if (newCapacity < 0) // overflow          // overflow-conscious code
283              newCapacity = Integer.MAX_VALUE;          if (newCapacity - MAX_ARRAY_SIZE > 0)
284          if (newCapacity < minCapacity)              newCapacity = hugeCapacity(minCapacity);
             newCapacity = minCapacity;  
285          queue = Arrays.copyOf(queue, newCapacity);          queue = Arrays.copyOf(queue, newCapacity);
286      }      }
287    
288        private static int hugeCapacity(int minCapacity) {
289            if (minCapacity < 0) // overflow
290                throw new OutOfMemoryError();
291            return (minCapacity > MAX_ARRAY_SIZE) ?
292                Integer.MAX_VALUE :
293                MAX_ARRAY_SIZE;
294        }
295    
296      /**      /**
297       * Inserts the specified element into this priority queue.       * Inserts the specified element into this priority queue.
298       *       *
299       * @return <tt>true</tt> (as specified by {@link Collection#add})       * @return {@code true} (as specified by {@link Collection#add})
300       * @throws ClassCastException if the specified element cannot be       * @throws ClassCastException if the specified element cannot be
301       *         compared with elements currently in this priority queue       *         compared with elements currently in this priority queue
302       *         according to the priority queue's ordering       *         according to the priority queue's ordering
# Line 252  Line 309 
309      /**      /**
310       * Inserts the specified element into this priority queue.       * Inserts the specified element into this priority queue.
311       *       *
312       * @return <tt>true</tt> (as specified by {@link Queue#offer})       * @return {@code true} (as specified by {@link Queue#offer})
313       * @throws ClassCastException if the specified element cannot be       * @throws ClassCastException if the specified element cannot be
314       *         compared with elements currently in this priority queue       *         compared with elements currently in this priority queue
315       *         according to the priority queue's ordering       *         according to the priority queue's ordering
# Line 274  Line 331 
331      }      }
332    
333      public E peek() {      public E peek() {
334          if (size == 0)          return (size == 0) ? null : (E) queue[0];
             return null;  
         return (E) queue[0];  
335      }      }
336    
337      private int indexOf(Object o) {      private int indexOf(Object o) {
# Line 290  Line 345 
345    
346      /**      /**
347       * Removes a single instance of the specified element from this queue,       * Removes a single instance of the specified element from this queue,
348       * if it is present.  More formally, removes an element <tt>e</tt> such       * if it is present.  More formally, removes an element {@code e} such
349       * that <tt>o.equals(e)</tt>, if this queue contains one or more such       * that {@code o.equals(e)}, if this queue contains one or more such
350       * elements.  Returns true if this queue contained the specified element       * elements.  Returns {@code true} if and only if this queue contained
351       * (or equivalently, if this queue changed as a result of the call).       * the specified element (or equivalently, if this queue changed as a
352         * result of the call).
353       *       *
354       * @param o element to be removed from this queue, if present       * @param o element to be removed from this queue, if present
355       * @return <tt>true</tt> if this queue changed as a result of the call       * @return {@code true} if this queue changed as a result of the call
356       */       */
357      public boolean remove(Object o) {      public boolean remove(Object o) {
358          int i = indexOf(o);          int i = indexOf(o);
# Line 313  Line 369 
369       * Needed by iterator.remove.       * Needed by iterator.remove.
370       *       *
371       * @param o element to be removed from this queue, if present       * @param o element to be removed from this queue, if present
372       * @return <tt>true</tt> if removed       * @return {@code true} if removed
373       */       */
374      boolean removeEq(Object o) {      boolean removeEq(Object o) {
375          for (int i = 0; i < size; i++) {          for (int i = 0; i < size; i++) {
# Line 326  Line 382 
382      }      }
383    
384      /**      /**
385       * Returns <tt>true</tt> if this queue contains the specified element.       * Returns {@code true} if this queue contains the specified element.
386       * More formally, returns <tt>true</tt> if and only if this queue contains       * More formally, returns {@code true} if and only if this queue contains
387       * at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.       * at least one element {@code e} such that {@code o.equals(e)}.
388       *       *
389       * @param o object to be checked for containment in this queue       * @param o object to be checked for containment in this queue
390       * @return <tt>true</tt> if this queue contains the specified element       * @return {@code true} if this queue contains the specified element
391       */       */
392      public boolean contains(Object o) {      public boolean contains(Object o) {
393          return indexOf(o) != -1;          return indexOf(o) != -1;
394      }      }
395    
396      /**      /**
397       * Returns an array containing all of the elements in this queue,       * Returns an array containing all of the elements in this queue.
398       * The elements are in no particular order.       * The elements are in no particular order.
399       *       *
400       * <p>The returned array will be "safe" in that no references to it are       * <p>The returned array will be "safe" in that no references to it are
401       * maintained by this list.  (In other words, this method must allocate       * maintained by this queue.  (In other words, this method must allocate
402       * a new array).  The caller is thus free to modify the returned array.       * a new array).  The caller is thus free to modify the returned array.
403       *       *
404         * <p>This method acts as bridge between array-based and collection-based
405         * APIs.
406         *
407       * @return an array containing all of the elements in this queue       * @return an array containing all of the elements in this queue
408       */       */
409      public Object[] toArray() {      public Object[] toArray() {
# Line 352  Line 411 
411      }      }
412    
413      /**      /**
414       * Returns an array containing all of the elements in this queue.       * Returns an array containing all of the elements in this queue; the
415       * The elements are in no particular order.  The runtime type of       * runtime type of the returned array is that of the specified array.
416       * the returned array is that of the specified array.  If the queue       * The returned array elements are in no particular order.
417       * fits in the specified array, it is returned therein.       * If the queue fits in the specified array, it is returned therein.
418       * Otherwise, a new array is allocated with the runtime type of       * Otherwise, a new array is allocated with the runtime type of the
419       * the specified array and the size of this queue.       * specified array and the size of this queue.
420       *       *
421       * <p>If the queue fits in the specified array with room to spare       * <p>If the queue fits in the specified array with room to spare
422       * (i.e., the array has more elements than the queue), the element in       * (i.e., the array has more elements than the queue), the element in
423       * the array immediately following the end of the collection is set to       * the array immediately following the end of the collection is set to
424       * <tt>null</tt>.  (This is useful in determining the length of the       * {@code null}.
425       * queue <i>only</i> if the caller knows that the queue does not contain       *
426       * any null elements.)       * <p>Like the {@link #toArray()} method, this method acts as bridge between
427         * array-based and collection-based APIs.  Further, this method allows
428         * precise control over the runtime type of the output array, and may,
429         * under certain circumstances, be used to save allocation costs.
430         *
431         * <p>Suppose <tt>x</tt> is a queue known to contain only strings.
432         * The following code can be used to dump the queue into a newly
433         * allocated array of <tt>String</tt>:
434         *
435         *  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
436         *
437         * Note that <tt>toArray(new Object[0])</tt> is identical in function to
438         * <tt>toArray()</tt>.
439       *       *
440       * @param a the array into which the elements of the queue are to       * @param a the array into which the elements of the queue are to
441       *          be stored, if it is big enough; otherwise, a new array of the       *          be stored, if it is big enough; otherwise, a new array of the
442       *          same runtime type is allocated for this purpose.       *          same runtime type is allocated for this purpose.
443       * @return an array containing the elements of the queue       * @return an array containing all of the elements in this queue
444       * @throws ArrayStoreException if the runtime type of the specified array       * @throws ArrayStoreException if the runtime type of the specified array
445       *         is not a supertype of the runtime type of every element in       *         is not a supertype of the runtime type of every element in
446       *         this queue       *         this queue
# Line 418  Line 489 
489           * after we've completed the "normal" iteration.           * after we've completed the "normal" iteration.
490           *           *
491           * We expect that most iterations, even those involving removals,           * We expect that most iterations, even those involving removals,
492           * will not use need to store elements in this field.           * will not need to store elements in this field.
493           */           */
494          private ArrayDeque<E> forgetMeNot = null;          private ArrayDeque<E> forgetMeNot = null;
495    
# Line 430  Line 501 
501    
502          /**          /**
503           * The modCount value that the iterator believes that the backing           * The modCount value that the iterator believes that the backing
504           * List should have.  If this expectation is violated, the iterator           * Queue should have.  If this expectation is violated, the iterator
505           * has detected concurrent modification.           * has detected concurrent modification.
506           */           */
507          private int expectedModCount = modCount;          private int expectedModCount = modCount;
# Line 457  Line 528 
528          public void remove() {          public void remove() {
529              if (expectedModCount != modCount)              if (expectedModCount != modCount)
530                  throw new ConcurrentModificationException();                  throw new ConcurrentModificationException();
             if (lastRet == -1 && lastRetElt == null)  
                 throw new IllegalStateException();  
531              if (lastRet != -1) {              if (lastRet != -1) {
532                  E moved = PriorityQueue.this.removeAt(lastRet);                  E moved = PriorityQueue.this.removeAt(lastRet);
533                  lastRet = -1;                  lastRet = -1;
# Line 469  Line 538 
538                          forgetMeNot = new ArrayDeque<E>();                          forgetMeNot = new ArrayDeque<E>();
539                      forgetMeNot.add(moved);                      forgetMeNot.add(moved);
540                  }                  }
541              } else {              } else if (lastRetElt != null) {
542                  PriorityQueue.this.removeEq(lastRetElt);                  PriorityQueue.this.removeEq(lastRetElt);
543                  lastRetElt = null;                  lastRetElt = null;
544                } else {
545                    throw new IllegalStateException();
546              }              }
547              expectedModCount = modCount;              expectedModCount = modCount;
548          }          }
   
549      }      }
550    
551      public int size() {      public int size() {
# Line 516  Line 586 
586       * i.  Under these circumstances, this method returns the element       * i.  Under these circumstances, this method returns the element
587       * that was previously at the end of the list and is now at some       * that was previously at the end of the list and is now at some
588       * position before i. This fact is used by iterator.remove so as to       * position before i. This fact is used by iterator.remove so as to
589       * avoid missing traverseing elements.       * avoid missing traversing elements.
590       */       */
591      private E removeAt(int i) {      private E removeAt(int i) {
592          assert i >= 0 && i < size;          assert i >= 0 && i < size;
# Line 642  Line 712 
712    
713      /**      /**
714       * Returns the comparator used to order the elements in this       * Returns the comparator used to order the elements in this
715       * queue, or <tt>null</tt> if this queue is sorted according to       * queue, or {@code null} if this queue is sorted according to
716       * the {@linkplain Comparable natural ordering} of its elements.       * the {@linkplain Comparable natural ordering} of its elements.
717       *       *
718       * @return the comparator used to order this queue, or       * @return the comparator used to order this queue, or
719       *         <tt>null</tt> if this queue is sorted according to the       *         {@code null} if this queue is sorted according to the
720       *         natural ordering of its elements.       *         natural ordering of its elements
721       */       */
722      public Comparator<? super E> comparator() {      public Comparator<? super E> comparator() {
723          return comparator;          return comparator;
724      }      }
725    
726      /**      /**
727       * Save the state of the instance to a stream (that       * Saves the state of the instance to a stream (that
728       * is, serialize it).       * is, serializes it).
729       *       *
730       * @serialData The length of the array backing the instance is       * @serialData The length of the array backing the instance is
731       * emitted (int), followed by all of its elements (each an       *             emitted (int), followed by all of its elements
732       * <tt>Object</tt>) in the proper order.       *             (each an {@code Object}) in the proper order.
733       * @param s the stream       * @param s the stream
734       */       */
735      private void writeObject(java.io.ObjectOutputStream s)      private void writeObject(java.io.ObjectOutputStream s)
# Line 667  Line 737 
737          // Write out element count, and any hidden stuff          // Write out element count, and any hidden stuff
738          s.defaultWriteObject();          s.defaultWriteObject();
739    
740          // Write out array length          // Write out array length, for compatibility with 1.5 version
741          // For compatibility with 1.5 version, must be at least 2.          s.writeInt(Math.max(2, size + 1));
         s.writeInt(Math.max(2, queue.length));  
742    
743          // Write out all elements in the proper order.          // Write out all elements in the "proper order".
744          for (int i=0; i<size; i++)          for (int i=0; i<size; i++)
745              s.writeObject(queue[i]);              s.writeObject(queue[i]);
746      }      }
747    
748      /**      /**
749       * Reconstitute the <tt>PriorityQueue</tt> instance from a stream       * Reconstitutes the {@code PriorityQueue} instance from a stream
750       * (that is, deserialize it).       * (that is, deserializes it).
751         *
752       * @param s the stream       * @param s the stream
753       */       */
754      private void readObject(java.io.ObjectInputStream s)      private void readObject(java.io.ObjectInputStream s)
# Line 686  Line 756 
756          // Read in size, and any hidden stuff          // Read in size, and any hidden stuff
757          s.defaultReadObject();          s.defaultReadObject();
758    
759          // Read in array length and allocate array          // Read in (and discard) array length
760          int arrayLength = s.readInt();          s.readInt();
761          queue = new Object[arrayLength];  
762            queue = new Object[size];
763    
764          // Read in all elements in the proper order.          // Read in all elements.
765          for (int i=0; i<size; i++)          for (int i=0; i<size; i++)
766              queue[i] = (E) s.readObject();              queue[i] = s.readObject();
     }  
767    
768            // Elements are guaranteed to be in "proper order", but the
769            // spec has never explained what that might be.
770            heapify();
771        }
772  }  }

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