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revision 1.61, Tue Feb 7 20:54:24 2006 UTC revision 1.88, Fri Feb 1 16:23:04 2013 UTC
# Line 1  Line 1 
1  /*  /*
2   * %W% %E%   * Copyright (c) 2003, 2012, 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.  Oracle designates this
8     * particular file as subject to the "Classpath" exception as provided
9     * by Oracle 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    import java.util.stream.Stream;
28    import java.util.Spliterator;
29    import java.util.stream.Streams;
30    import java.util.function.Consumer;
31    
32  /**  /**
33   * An unbounded priority {@linkplain Queue queue} based on a priority   * An unbounded priority {@linkplain Queue queue} based on a priority heap.
34   * heap.  The elements of the priority queue are ordered according to   * The elements of the priority queue are ordered according to their
35   * their {@linkplain Comparable natural ordering}, or by a {@link   * {@linkplain Comparable natural ordering}, or by a {@link Comparator}
36   * Comparator} provided at queue construction time, depending on which   * provided at queue construction time, depending on which constructor is
37   * constructor is used.  A priority queue does not permit   * used.  A priority queue does not permit {@code null} elements.
38   * <tt>null</tt> elements.  A priority queue relying on natural   * A priority queue relying on natural ordering also does not permit
39   * ordering also does not permit insertion of non-comparable objects   * insertion of non-comparable objects (doing so may result in
40   * (doing so may result in <tt>ClassCastException</tt>).   * {@code ClassCastException}).
41   *   *
42   * <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
43   * with respect to the specified ordering.  If multiple elements are   * with respect to the specified ordering.  If multiple elements are
44   * 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
45   * broken arbitrarily.  The queue retrieval operations <tt>poll</tt>,   * broken arbitrarily.  The queue retrieval operations {@code poll},
46   * <tt>remove</tt>, <tt>peek</tt>, and <tt>element</tt> access the   * {@code remove}, {@code peek}, and {@code element} access the
47   * element at the head of the queue.   * element at the head of the queue.
48   *   *
49   * <p>A priority queue is unbounded, but has an internal   * <p>A priority queue is unbounded, but has an internal
# Line 36  Line 58 
58   * Iterator} interfaces.  The Iterator provided in method {@link   * Iterator} interfaces.  The Iterator provided in method {@link
59   * #iterator()} is <em>not</em> guaranteed to traverse the elements of   * #iterator()} is <em>not</em> guaranteed to traverse the elements of
60   * the priority queue in any particular order. If you need ordered   * the priority queue in any particular order. If you need ordered
61   * traversal, consider using <tt>Arrays.sort(pq.toArray())</tt>.   * traversal, consider using {@code Arrays.sort(pq.toArray())}.
62   *   *
63   * <p> <strong>Note that this implementation is not synchronized.</strong>   * <p> <strong>Note that this implementation is not synchronized.</strong>
64   * Multiple threads should not access a <tt>PriorityQueue</tt>   * Multiple threads should not access a {@code PriorityQueue}
65   * instance concurrently if any of the threads modifies the list   * instance concurrently if any of the threads modifies the queue.
66   * structurally. Instead, use the thread-safe {@link   * Instead, use the thread-safe {@link
67   * java.util.concurrent.PriorityBlockingQueue} class.   * java.util.concurrent.PriorityBlockingQueue} class.
68   *   *
69   * <p>Implementation note: this implementation provides O(log(n)) time   * <p>Implementation note: this implementation provides
70   * for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,   * O(log(n)) time for the enqueing and dequeing methods
71   * <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the   * ({@code offer}, {@code poll}, {@code remove()} and {@code add});
72   * <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and   * linear time for the {@code remove(Object)} and {@code contains(Object)}
73   * constant time for the retrieval methods (<tt>peek</tt>,   * methods; and constant time for the retrieval methods
74   * <tt>element</tt>, and <tt>size</tt>).   * ({@code peek}, {@code element}, and {@code size}).
75   *   *
76   * <p>This class is a member of the   * <p>This class is a member of the
77   * <a href="{@docRoot}/../guide/collections/index.html">   * <a href="{@docRoot}/../technotes/guides/collections/index.html">
78   * Java Collections Framework</a>.   * Java Collections Framework</a>.
79     *
80   * @since 1.5   * @since 1.5
81   * @version 1.8, 08/27/05   * @author Josh Bloch, Doug Lea
  * @author Josh Bloch  
82   * @param <E> the type of elements held in this collection   * @param <E> the type of elements held in this collection
83   */   */
84  public class PriorityQueue<E> extends AbstractQueue<E>  public class PriorityQueue<E> extends AbstractQueue<E>
# Line 74  Line 96 
96       * heap and each descendant d of n, n <= d.  The element with the       * heap and each descendant d of n, n <= d.  The element with the
97       * lowest value is in queue[0], assuming the queue is nonempty.       * lowest value is in queue[0], assuming the queue is nonempty.
98       */       */
99      private transient Object[] queue;      transient Object[] queue; // non-private to simplify nested class access
100    
101      /**      /**
102       * The number of elements in the priority queue.       * The number of elements in the priority queue.
# Line 91  Line 113 
113       * The number of times this priority queue has been       * The number of times this priority queue has been
114       * <i>structurally modified</i>.  See AbstractList for gory details.       * <i>structurally modified</i>.  See AbstractList for gory details.
115       */       */
116      private transient int modCount = 0;      transient int modCount = 0; // non-private to simplify nested class access
117    
118      /**      /**
119       * Creates a <tt>PriorityQueue</tt> with the default initial       * Creates a {@code PriorityQueue} with the default initial
120       * capacity (11) that orders its elements according to their       * capacity (11) that orders its elements according to their
121       * {@linkplain Comparable natural ordering}.       * {@linkplain Comparable natural ordering}.
122       */       */
# Line 103  Line 125 
125      }      }
126    
127      /**      /**
128       * Creates a <tt>PriorityQueue</tt> with the specified initial       * Creates a {@code PriorityQueue} with the specified initial
129       * capacity that orders its elements according to their       * capacity that orders its elements according to their
130       * {@linkplain Comparable natural ordering}.       * {@linkplain Comparable natural ordering}.
131       *       *
132       * @param initialCapacity the initial capacity for this priority queue       * @param initialCapacity the initial capacity for this priority queue
133       * @throws IllegalArgumentException if <tt>initialCapacity</tt> is less       * @throws IllegalArgumentException if {@code initialCapacity} is less
134       * than 1       * than 1
135       */       */
136      public PriorityQueue(int initialCapacity) {      public PriorityQueue(int initialCapacity) {
# Line 116  Line 138 
138      }      }
139    
140      /**      /**
141       * Creates a <tt>PriorityQueue</tt> with the specified initial capacity       * Creates a {@code PriorityQueue} with the specified initial capacity
142       * that orders its elements according to the specified comparator.       * that orders its elements according to the specified comparator.
143       *       *
144       * @param  initialCapacity the initial capacity for this priority queue       * @param  initialCapacity the initial capacity for this priority queue
145       * @param  comparator the comparator that will be used to order       * @param  comparator the comparator that will be used to order this
146       *         this priority queue.  If <tt>null</tt>, the <i>natural       *         priority queue.  If {@code null}, the {@linkplain Comparable
147       *         ordering</i> of the elements will be used.       *         natural ordering} of the elements will be used.
148       * @throws IllegalArgumentException if <tt>initialCapacity</tt> is       * @throws IllegalArgumentException if {@code initialCapacity} is
149       *         less than 1       *         less than 1
150       */       */
151      public PriorityQueue(int initialCapacity,      public PriorityQueue(int initialCapacity,
# Line 137  Line 159 
159      }      }
160    
161      /**      /**
162       * Creates a <tt>PriorityQueue</tt> containing the elements in the       * Creates a {@code PriorityQueue} containing the elements in the
163       * specified collection.   If the specified collection is an       * specified collection.  If the specified collection is an instance of
164       * instance of a {@link java.util.SortedSet} or is another       * a {@link SortedSet} or is another {@code PriorityQueue}, this
165       * <tt>PriorityQueue</tt>, the priority queue will be ordered       * priority queue will be ordered according to the same ordering.
166       * according to the same ordering.  Otherwise, this priority queue       * Otherwise, this priority queue will be ordered according to the
167       * will be ordered according to the natural ordering of its elements.       * {@linkplain Comparable natural ordering} of its elements.
168       *       *
169       * @param  c the collection whose elements are to be placed       * @param  c the collection whose elements are to be placed
170       *         into this priority queue       *         into this priority queue
# Line 152  Line 174 
174       * @throws NullPointerException if the specified collection or any       * @throws NullPointerException if the specified collection or any
175       *         of its elements are null       *         of its elements are null
176       */       */
177        @SuppressWarnings("unchecked")
178      public PriorityQueue(Collection<? extends E> c) {      public PriorityQueue(Collection<? extends E> c) {
179          initFromCollection(c);          if (c instanceof SortedSet<?>) {
180          if (c instanceof SortedSet)              SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
181              comparator = (Comparator<? super E>)              this.comparator = (Comparator<? super E>) ss.comparator();
182                  ((SortedSet<? extends E>)c).comparator();              initElementsFromCollection(ss);
183          else if (c instanceof PriorityQueue)          }
184              comparator = (Comparator<? super E>)          else if (c instanceof PriorityQueue<?>) {
185                  ((PriorityQueue<? extends E>)c).comparator();              PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
186                this.comparator = (Comparator<? super E>) pq.comparator();
187                initFromPriorityQueue(pq);
188            }
189          else {          else {
190              comparator = null;              this.comparator = null;
191              heapify();              initFromCollection(c);
192          }          }
193      }      }
194    
195      /**      /**
196       * Creates a <tt>PriorityQueue</tt> containing the elements in the       * Creates a {@code PriorityQueue} containing the elements in the
197       * specified priority queue.  This priority queue will be       * specified priority queue.  This priority queue will be
198       * ordered according to the same ordering as the given priority       * ordered according to the same ordering as the given priority
199       * queue.       * queue.
200       *       *
201       * @param  c the priority queue whose elements are to be placed       * @param  c the priority queue whose elements are to be placed
202       *         into this priority queue       *         into this priority queue
203       * @throws ClassCastException if elements of <tt>c</tt> cannot be       * @throws ClassCastException if elements of {@code c} cannot be
204       *         compared to one another according to <tt>c</tt>'s       *         compared to one another according to {@code c}'s
205       *         ordering       *         ordering
206       * @throws NullPointerException if the specified priority queue or any       * @throws NullPointerException if the specified priority queue or any
207       *         of its elements are null       *         of its elements are null
208       */       */
209        @SuppressWarnings("unchecked")
210      public PriorityQueue(PriorityQueue<? extends E> c) {      public PriorityQueue(PriorityQueue<? extends E> c) {
211          comparator = (Comparator<? super E>)c.comparator();          this.comparator = (Comparator<? super E>) c.comparator();
212          initFromCollection(c);          initFromPriorityQueue(c);
213      }      }
214    
215      /**      /**
216       * Creates a <tt>PriorityQueue</tt> containing the elements in the       * Creates a {@code PriorityQueue} containing the elements in the
217       * specified sorted set.  This priority queue will be ordered       * specified sorted set.  This priority queue will be ordered
218       * according to the same ordering as the given sorted set.       * according to the same ordering as the given sorted set.
219       *       *
220       * @param  c the sorted set whose elements are to be placed       * @param  c the sorted set whose elements are to be placed
221       *         into this priority queue.       *         into this priority queue
222       * @throws ClassCastException if elements of the specified sorted       * @throws ClassCastException if elements of the specified sorted
223       *         set cannot be compared to one another according to the       *         set cannot be compared to one another according to the
224       *         sorted set's ordering       *         sorted set's ordering
225       * @throws NullPointerException if the specified sorted set or any       * @throws NullPointerException if the specified sorted set or any
226       *         of its elements are null       *         of its elements are null
227       */       */
228        @SuppressWarnings("unchecked")
229      public PriorityQueue(SortedSet<? extends E> c) {      public PriorityQueue(SortedSet<? extends E> c) {
230          comparator = (Comparator<? super E>)c.comparator();          this.comparator = (Comparator<? super E>) c.comparator();
231            initElementsFromCollection(c);
232        }
233    
234        private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
235            if (c.getClass() == PriorityQueue.class) {
236                this.queue = c.toArray();
237                this.size = c.size();
238            } else {
239          initFromCollection(c);          initFromCollection(c);
240      }      }
241        }
242    
243      /**      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) {  
244          Object[] a = c.toArray();          Object[] a = c.toArray();
245          // If c.toArray incorrectly doesn't return Object[], copy it.          // If c.toArray incorrectly doesn't return Object[], copy it.
246          if (a.getClass() != Object[].class)          if (a.getClass() != Object[].class)
247              a = Arrays.copyOf(a, a.length, Object[].class);              a = Arrays.copyOf(a, a.length, Object[].class);
248          queue = a;          int len = a.length;
249          size = a.length;          if (len == 1 || this.comparator != null)
250                for (int i = 0; i < len; i++)
251                    if (a[i] == null)
252                        throw new NullPointerException();
253            this.queue = a;
254            this.size = a.length;
255      }      }
256    
257      /**      /**
258         * Initializes queue array with elements from the given Collection.
259         *
260         * @param c the collection
261         */
262        private void initFromCollection(Collection<? extends E> c) {
263            initElementsFromCollection(c);
264            heapify();
265        }
266    
267        /**
268         * The maximum size of array to allocate.
269         * Some VMs reserve some header words in an array.
270         * Attempts to allocate larger arrays may result in
271         * OutOfMemoryError: Requested array size exceeds VM limit
272         */
273        private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
274    
275        /**
276       * Increases the capacity of the array.       * Increases the capacity of the array.
277       *       *
278       * @param minCapacity the desired minimum capacity       * @param minCapacity the desired minimum capacity
279       */       */
280      private void grow(int minCapacity) {      private void grow(int minCapacity) {
         if (minCapacity < 0) // overflow  
             throw new OutOfMemoryError();  
281          int oldCapacity = queue.length;          int oldCapacity = queue.length;
282          // Double size if small; else grow by 50%          // Double size if small; else grow by 50%
283          int newCapacity = ((oldCapacity < 64)?          int newCapacity = oldCapacity + ((oldCapacity < 64) ?
284                             ((oldCapacity + 1) * 2):                                           (oldCapacity + 2) :
285                             ((oldCapacity / 2) * 3));                                           (oldCapacity >> 1));
286          if (newCapacity < 0) // overflow          // overflow-conscious code
287              newCapacity = Integer.MAX_VALUE;          if (newCapacity - MAX_ARRAY_SIZE > 0)
288          if (newCapacity < minCapacity)              newCapacity = hugeCapacity(minCapacity);
             newCapacity = minCapacity;  
289          queue = Arrays.copyOf(queue, newCapacity);          queue = Arrays.copyOf(queue, newCapacity);
290      }      }
291    
292        private static int hugeCapacity(int minCapacity) {
293            if (minCapacity < 0) // overflow
294                throw new OutOfMemoryError();
295            return (minCapacity > MAX_ARRAY_SIZE) ?
296                Integer.MAX_VALUE :
297                MAX_ARRAY_SIZE;
298        }
299    
300      /**      /**
301       * Inserts the specified element into this priority queue.       * Inserts the specified element into this priority queue.
302       *       *
303       * @return <tt>true</tt> (as specified by {@link Collection#add})       * @return {@code true} (as specified by {@link Collection#add})
304       * @throws ClassCastException if the specified element cannot be       * @throws ClassCastException if the specified element cannot be
305       *         compared with elements currently in this priority queue       *         compared with elements currently in this priority queue
306       *         according to the priority queue's ordering       *         according to the priority queue's ordering
# Line 252  Line 313 
313      /**      /**
314       * Inserts the specified element into this priority queue.       * Inserts the specified element into this priority queue.
315       *       *
316       * @return <tt>true</tt> (as specified by {@link Queue#offer})       * @return {@code true} (as specified by {@link Queue#offer})
317       * @throws ClassCastException if the specified element cannot be       * @throws ClassCastException if the specified element cannot be
318       *         compared with elements currently in this priority queue       *         compared with elements currently in this priority queue
319       *         according to the priority queue's ordering       *         according to the priority queue's ordering
# Line 273  Line 334 
334          return true;          return true;
335      }      }
336    
337        @SuppressWarnings("unchecked")
338      public E peek() {      public E peek() {
339          if (size == 0)          return (size == 0) ? null : (E) queue[0];
             return null;  
         return (E) queue[0];  
340      }      }
341    
342      private int indexOf(Object o) {      private int indexOf(Object o) {
# Line 290  Line 350 
350    
351      /**      /**
352       * Removes a single instance of the specified element from this queue,       * Removes a single instance of the specified element from this queue,
353       * 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
354       * 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
355       * elements.  Returns true if this queue contained the specified element       * elements.  Returns {@code true} if and only if this queue contained
356       * (or equivalently, if this queue changed as a result of the call).       * the specified element (or equivalently, if this queue changed as a
357         * result of the call).
358       *       *
359       * @param o element to be removed from this queue, if present       * @param o element to be removed from this queue, if present
360       * @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
361       */       */
362      public boolean remove(Object o) {      public boolean remove(Object o) {
363          int i = indexOf(o);          int i = indexOf(o);
# Line 313  Line 374 
374       * Needed by iterator.remove.       * Needed by iterator.remove.
375       *       *
376       * @param o element to be removed from this queue, if present       * @param o element to be removed from this queue, if present
377       * @return <tt>true</tt> if removed       * @return {@code true} if removed
378       */       */
379      boolean removeEq(Object o) {      boolean removeEq(Object o) {
380          for (int i = 0; i < size; i++) {          for (int i = 0; i < size; i++) {
# Line 326  Line 387 
387      }      }
388    
389      /**      /**
390       * Returns <tt>true</tt> if this queue contains the specified element.       * Returns {@code true} if this queue contains the specified element.
391       * 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
392       * 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)}.
393       *       *
394       * @param o object to be checked for containment in this queue       * @param o object to be checked for containment in this queue
395       * @return <tt>true</tt> if this queue contains the specified element       * @return {@code true} if this queue contains the specified element
396       */       */
397      public boolean contains(Object o) {      public boolean contains(Object o) {
398          return indexOf(o) != -1;          return indexOf(o) != -1;
399      }      }
400    
401      /**      /**
402       * Returns an array containing all of the elements in this queue,       * Returns an array containing all of the elements in this queue.
403       * The elements are in no particular order.       * The elements are in no particular order.
404       *       *
405       * <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
406       * maintained by this list.  (In other words, this method must allocate       * maintained by this queue.  (In other words, this method must allocate
407       * 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.
408       *       *
409         * <p>This method acts as bridge between array-based and collection-based
410         * APIs.
411         *
412       * @return an array containing all of the elements in this queue       * @return an array containing all of the elements in this queue
413       */       */
414      public Object[] toArray() {      public Object[] toArray() {
# Line 352  Line 416 
416      }      }
417    
418      /**      /**
419       * Returns an array containing all of the elements in this queue.       * Returns an array containing all of the elements in this queue; the
420       * The elements are in no particular order.  The runtime type of       * runtime type of the returned array is that of the specified array.
421       * the returned array is that of the specified array.  If the queue       * The returned array elements are in no particular order.
422       * fits in the specified array, it is returned therein.       * If the queue fits in the specified array, it is returned therein.
423       * Otherwise, a new array is allocated with the runtime type of       * Otherwise, a new array is allocated with the runtime type of the
424       * the specified array and the size of this queue.       * specified array and the size of this queue.
425       *       *
426       * <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
427       * (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
428       * the array immediately following the end of the collection is set to       * the array immediately following the end of the collection is set to
429       * <tt>null</tt>.  (This is useful in determining the length of the       * {@code null}.
430       * queue <i>only</i> if the caller knows that the queue does not contain       *
431       * any null elements.)       * <p>Like the {@link #toArray()} method, this method acts as bridge between
432         * array-based and collection-based APIs.  Further, this method allows
433         * precise control over the runtime type of the output array, and may,
434         * under certain circumstances, be used to save allocation costs.
435         *
436         * <p>Suppose {@code x} is a queue known to contain only strings.
437         * The following code can be used to dump the queue into a newly
438         * allocated array of {@code String}:
439         *
440         *  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
441         *
442         * Note that {@code toArray(new Object[0])} is identical in function to
443         * {@code toArray()}.
444       *       *
445       * @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
446       *          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
447       *          same runtime type is allocated for this purpose.       *          same runtime type is allocated for this purpose.
448       * @return an array containing the elements of the queue       * @return an array containing all of the elements in this queue
449       * @throws ArrayStoreException if the runtime type of the specified array       * @throws ArrayStoreException if the runtime type of the specified array
450       *         is not a supertype of the runtime type of every element in       *         is not a supertype of the runtime type of every element in
451       *         this queue       *         this queue
452       * @throws NullPointerException if the specified array is null       * @throws NullPointerException if the specified array is null
453       */       */
454        @SuppressWarnings("unchecked")
455      public <T> T[] toArray(T[] a) {      public <T> T[] toArray(T[] a) {
456            final int size = this.size;
457          if (a.length < size)          if (a.length < size)
458              // Make a new array of a's runtime type, but my contents:              // Make a new array of a's runtime type, but my contents:
459              return (T[]) Arrays.copyOf(queue, size, a.getClass());              return (T[]) Arrays.copyOf(queue, size, a.getClass());
# Line 418  Line 496 
496           * after we've completed the "normal" iteration.           * after we've completed the "normal" iteration.
497           *           *
498           * We expect that most iterations, even those involving removals,           * We expect that most iterations, even those involving removals,
499           * will not use need to store elements in this field.           * will not need to store elements in this field.
500           */           */
501          private ArrayDeque<E> forgetMeNot = null;          private ArrayDeque<E> forgetMeNot = null;
502    
# Line 430  Line 508 
508    
509          /**          /**
510           * The modCount value that the iterator believes that the backing           * The modCount value that the iterator believes that the backing
511           * List should have.  If this expectation is violated, the iterator           * Queue should have.  If this expectation is violated, the iterator
512           * has detected concurrent modification.           * has detected concurrent modification.
513           */           */
514          private int expectedModCount = modCount;          private int expectedModCount = modCount;
# Line 440  Line 518 
518                  (forgetMeNot != null && !forgetMeNot.isEmpty());                  (forgetMeNot != null && !forgetMeNot.isEmpty());
519          }          }
520    
521            @SuppressWarnings("unchecked")
522          public E next() {          public E next() {
523              if (expectedModCount != modCount)              if (expectedModCount != modCount)
524                  throw new ConcurrentModificationException();                  throw new ConcurrentModificationException();
# Line 457  Line 536 
536          public void remove() {          public void remove() {
537              if (expectedModCount != modCount)              if (expectedModCount != modCount)
538                  throw new ConcurrentModificationException();                  throw new ConcurrentModificationException();
             if (lastRet == -1 && lastRetElt == null)  
                 throw new IllegalStateException();  
539              if (lastRet != -1) {              if (lastRet != -1) {
540                  E moved = PriorityQueue.this.removeAt(lastRet);                  E moved = PriorityQueue.this.removeAt(lastRet);
541                  lastRet = -1;                  lastRet = -1;
# Line 469  Line 546 
546                          forgetMeNot = new ArrayDeque<E>();                          forgetMeNot = new ArrayDeque<E>();
547                      forgetMeNot.add(moved);                      forgetMeNot.add(moved);
548                  }                  }
549              } else {              } else if (lastRetElt != null) {
550                  PriorityQueue.this.removeEq(lastRetElt);                  PriorityQueue.this.removeEq(lastRetElt);
551                  lastRetElt = null;                  lastRetElt = null;
552                } else {
553                    throw new IllegalStateException();
554              }              }
555              expectedModCount = modCount;              expectedModCount = modCount;
556          }          }
   
557      }      }
558    
559      public int size() {      public int size() {
# Line 493  Line 571 
571          size = 0;          size = 0;
572      }      }
573    
574        @SuppressWarnings("unchecked")
575      public E poll() {      public E poll() {
576          if (size == 0)          if (size == 0)
577              return null;              return null;
# Line 516  Line 595 
595       * i.  Under these circumstances, this method returns the element       * i.  Under these circumstances, this method returns the element
596       * 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
597       * 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
598       * avoid missing traverseing elements.       * avoid missing traversing elements.
599       */       */
600        @SuppressWarnings("unchecked")
601      private E removeAt(int i) {      private E removeAt(int i) {
602          assert i >= 0 && i < size;          // assert i >= 0 && i < size;
603          modCount++;          modCount++;
604          int s = --size;          int s = --size;
605          if (s == i) // removed last element          if (s == i) // removed last element
# Line 556  Line 636 
636              siftUpComparable(k, x);              siftUpComparable(k, x);
637      }      }
638    
639        @SuppressWarnings("unchecked")
640      private void siftUpComparable(int k, E x) {      private void siftUpComparable(int k, E x) {
641          Comparable<? super E> key = (Comparable<? super E>) x;          Comparable<? super E> key = (Comparable<? super E>) x;
642          while (k > 0) {          while (k > 0) {
# Line 569  Line 650 
650          queue[k] = key;          queue[k] = key;
651      }      }
652    
653        @SuppressWarnings("unchecked")
654      private void siftUpUsingComparator(int k, E x) {      private void siftUpUsingComparator(int k, E x) {
655          while (k > 0) {          while (k > 0) {
656              int parent = (k - 1) >>> 1;              int parent = (k - 1) >>> 1;
# Line 596  Line 678 
678              siftDownComparable(k, x);              siftDownComparable(k, x);
679      }      }
680    
681        @SuppressWarnings("unchecked")
682      private void siftDownComparable(int k, E x) {      private void siftDownComparable(int k, E x) {
683          Comparable<? super E> key = (Comparable<? super E>)x;          Comparable<? super E> key = (Comparable<? super E>)x;
684          int half = size >>> 1;        // loop while a non-leaf          int half = size >>> 1;        // loop while a non-leaf
# Line 614  Line 697 
697          queue[k] = key;          queue[k] = key;
698      }      }
699    
700        @SuppressWarnings("unchecked")
701      private void siftDownUsingComparator(int k, E x) {      private void siftDownUsingComparator(int k, E x) {
702          int half = size >>> 1;          int half = size >>> 1;
703          while (k < half) {          while (k < half) {
# Line 635  Line 719 
719       * Establishes the heap invariant (described above) in the entire tree,       * Establishes the heap invariant (described above) in the entire tree,
720       * assuming nothing about the order of the elements prior to the call.       * assuming nothing about the order of the elements prior to the call.
721       */       */
722        @SuppressWarnings("unchecked")
723      private void heapify() {      private void heapify() {
724          for (int i = (size >>> 1) - 1; i >= 0; i--)          for (int i = (size >>> 1) - 1; i >= 0; i--)
725              siftDown(i, (E)queue[i]);              siftDown(i, (E)queue[i]);
# Line 642  Line 727 
727    
728      /**      /**
729       * Returns the comparator used to order the elements in this       * Returns the comparator used to order the elements in this
730       * queue, or <tt>null</tt> if this queue is sorted according to       * queue, or {@code null} if this queue is sorted according to
731       * the {@linkplain Comparable natural ordering} of its elements.       * the {@linkplain Comparable natural ordering} of its elements.
732       *       *
733       * @return the comparator used to order this queue, or       * @return the comparator used to order this queue, or
734       *         <tt>null</tt> if this queue is sorted according to the       *         {@code null} if this queue is sorted according to the
735       *         natural ordering of its elements.       *         natural ordering of its elements
736       */       */
737      public Comparator<? super E> comparator() {      public Comparator<? super E> comparator() {
738          return comparator;          return comparator;
739      }      }
740    
741      /**      /**
742       * Save the state of the instance to a stream (that       * Saves this queue to a stream (that is, serializes it).
      * is, serialize it).  
743       *       *
744       * @serialData The length of the array backing the instance is       * @serialData The length of the array backing the instance is
745       * emitted (int), followed by all of its elements (each an       *             emitted (int), followed by all of its elements
746       * <tt>Object</tt>) in the proper order.       *             (each an {@code Object}) in the proper order.
747       * @param s the stream       * @param s the stream
748       */       */
749      private void writeObject(java.io.ObjectOutputStream s)      private void writeObject(java.io.ObjectOutputStream s)
# Line 667  Line 751 
751          // Write out element count, and any hidden stuff          // Write out element count, and any hidden stuff
752          s.defaultWriteObject();          s.defaultWriteObject();
753    
754          // Write out array length          // Write out array length, for compatibility with 1.5 version
755          // 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));  
756    
757          // Write out all elements in the proper order.          // Write out all elements in the "proper order".
758          for (int i=0; i<size; i++)          for (int i=0; i<size; i++)
759              s.writeObject(queue[i]);              s.writeObject(queue[i]);
760      }      }
761    
762      /**      /**
763       * Reconstitute the <tt>PriorityQueue</tt> instance from a stream       * Reconstitutes the {@code PriorityQueue} instance from a stream
764       * (that is, deserialize it).       * (that is, deserializes it).
765         *
766       * @param s the stream       * @param s the stream
767       */       */
768      private void readObject(java.io.ObjectInputStream s)      private void readObject(java.io.ObjectInputStream s)
# Line 686  Line 770 
770          // Read in size, and any hidden stuff          // Read in size, and any hidden stuff
771          s.defaultReadObject();          s.defaultReadObject();
772    
773          // Read in array length and allocate array          // Read in (and discard) array length
774          int arrayLength = s.readInt();          s.readInt();
775          queue = new Object[arrayLength];  
776            queue = new Object[size];
777    
778          // Read in all elements in the proper order.          // Read in all elements.
779          for (int i=0; i<size; i++)          for (int i=0; i<size; i++)
780              queue[i] = (E) s.readObject();              queue[i] = s.readObject();
781    
782            // Elements are guaranteed to be in "proper order", but the
783            // spec has never explained what that might be.
784            heapify();
785        }
786    
787        // wrapping constructor in method avoids transient javac problems
788        final PriorityQueueSpliterator<E> spliterator(int origin, int fence,
789                                                      int expectedModCount) {
790            return new PriorityQueueSpliterator<E>(this, origin, fence,
791                                                   expectedModCount);
792        }
793    
794        public Stream<E> stream() {
795            int flags = Streams.STREAM_IS_SIZED;
796            return Streams.stream
797                (() -> spliterator(0, size, modCount), flags);
798        }
799        public Stream<E> parallelStream() {
800            int flags = Streams.STREAM_IS_SIZED;
801            return Streams.parallelStream
802                (() -> spliterator(0, size, modCount), flags);
803        }
804    
805        /** Index-based split-by-two Spliterator */
806        static final class PriorityQueueSpliterator<E> implements Spliterator<E> {
807            private final PriorityQueue<E> pq;
808            private int index;           // current index, modified on advance/split
809            private final int fence;     // one past last index
810            private final int expectedModCount; // for comodification checks
811    
812            /** Create new spliterator covering the given  range */
813            PriorityQueueSpliterator(PriorityQueue<E> pq, int origin, int fence,
814                                 int expectedModCount) {
815                this.pq = pq; this.index = origin; this.fence = fence;
816                this.expectedModCount = expectedModCount;
817            }
818    
819            public PriorityQueueSpliterator<E> trySplit() {
820                int lo = index, mid = (lo + fence) >>> 1;
821                return (lo >= mid) ? null :
822                    new PriorityQueueSpliterator<E>(pq, lo, index = mid,
823                                                    expectedModCount);
824            }
825    
826            public void forEach(Consumer<? super E> block) {
827                Object[] a; int i, hi; // hoist accesses and checks from loop
828                if (block == null)
829                    throw new NullPointerException();
830                if ((a = pq.queue).length >= (hi = fence) &&
831                    (i = index) >= 0 && i < hi) {
832                    index = hi;
833                    do {
834                        @SuppressWarnings("unchecked") E e = (E) a[i];
835                        block.accept(e);
836                    } while (++i < hi);
837                    if (pq.modCount != expectedModCount)
838                        throw new ConcurrentModificationException();
839                }
840            }
841    
842            public boolean tryAdvance(Consumer<? super E> block) {
843                if (index >= 0 && index < fence) {
844                    @SuppressWarnings("unchecked") E e =
845                        (E)pq.queue[index++];
846                    block.accept(e);
847                    if (pq.modCount != expectedModCount)
848                        throw new ConcurrentModificationException();
849                    return true;
850                }
851                return false;
852      }      }
853    
854            public long estimateSize() { return (long)(fence - index); }
855            public boolean hasExactSize() { return true; }
856            public boolean hasExactSplits() { return true; }
857        }
858  }  }

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