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revision 1.61, Tue Feb 7 20:54:24 2006 UTC revision 1.90, Mon Feb 18 01:30:23 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.function.Consumer;
28    import java.util.stream.Stream;
29    import java.util.stream.Streams;
30    
31  /**  /**
32   * An unbounded priority {@linkplain Queue queue} based on a priority   * An unbounded priority {@linkplain Queue queue} based on a priority heap.
33   * heap.  The elements of the priority queue are ordered according to   * The elements of the priority queue are ordered according to their
34   * their {@linkplain Comparable natural ordering}, or by a {@link   * {@linkplain Comparable natural ordering}, or by a {@link Comparator}
35   * Comparator} provided at queue construction time, depending on which   * provided at queue construction time, depending on which constructor is
36   * constructor is used.  A priority queue does not permit   * used.  A priority queue does not permit {@code null} elements.
37   * <tt>null</tt> elements.  A priority queue relying on natural   * A priority queue relying on natural ordering also does not permit
38   * ordering also does not permit insertion of non-comparable objects   * insertion of non-comparable objects (doing so may result in
39   * (doing so may result in <tt>ClassCastException</tt>).   * {@code ClassCastException}).
40   *   *
41   * <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
42   * with respect to the specified ordering.  If multiple elements are   * with respect to the specified ordering.  If multiple elements are
43   * 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
44   * broken arbitrarily.  The queue retrieval operations <tt>poll</tt>,   * broken arbitrarily.  The queue retrieval operations {@code poll},
45   * <tt>remove</tt>, <tt>peek</tt>, and <tt>element</tt> access the   * {@code remove}, {@code peek}, and {@code element} access the
46   * element at the head of the queue.   * element at the head of the queue.
47   *   *
48   * <p>A priority queue is unbounded, but has an internal   * <p>A priority queue is unbounded, but has an internal
# Line 36  Line 57 
57   * Iterator} interfaces.  The Iterator provided in method {@link   * Iterator} interfaces.  The Iterator provided in method {@link
58   * #iterator()} is <em>not</em> guaranteed to traverse the elements of   * #iterator()} is <em>not</em> guaranteed to traverse the elements of
59   * the priority queue in any particular order. If you need ordered   * the priority queue in any particular order. If you need ordered
60   * traversal, consider using <tt>Arrays.sort(pq.toArray())</tt>.   * traversal, consider using {@code Arrays.sort(pq.toArray())}.
61   *   *
62   * <p> <strong>Note that this implementation is not synchronized.</strong>   * <p> <strong>Note that this implementation is not synchronized.</strong>
63   * Multiple threads should not access a <tt>PriorityQueue</tt>   * Multiple threads should not access a {@code PriorityQueue}
64   * instance concurrently if any of the threads modifies the list   * instance concurrently if any of the threads modifies the queue.
65   * structurally. Instead, use the thread-safe {@link   * Instead, use the thread-safe {@link
66   * java.util.concurrent.PriorityBlockingQueue} class.   * java.util.concurrent.PriorityBlockingQueue} class.
67   *   *
68   * <p>Implementation note: this implementation provides O(log(n)) time   * <p>Implementation note: this implementation provides
69   * for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,   * O(log(n)) time for the enqueing and dequeing methods
70   * <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the   * ({@code offer}, {@code poll}, {@code remove()} and {@code add});
71   * <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and   * linear time for the {@code remove(Object)} and {@code contains(Object)}
72   * constant time for the retrieval methods (<tt>peek</tt>,   * methods; and constant time for the retrieval methods
73   * <tt>element</tt>, and <tt>size</tt>).   * ({@code peek}, {@code element}, and {@code size}).
74   *   *
75   * <p>This class is a member of the   * <p>This class is a member of the
76   * <a href="{@docRoot}/../guide/collections/index.html">   * <a href="{@docRoot}/../technotes/guides/collections/index.html">
77   * Java Collections Framework</a>.   * Java Collections Framework</a>.
78     *
79   * @since 1.5   * @since 1.5
80   * @version 1.8, 08/27/05   * @author Josh Bloch, Doug Lea
  * @author Josh Bloch  
81   * @param <E> the type of elements held in this collection   * @param <E> the type of elements held in this collection
82   */   */
83  public class PriorityQueue<E> extends AbstractQueue<E>  public class PriorityQueue<E> extends AbstractQueue<E>
# Line 74  Line 95 
95       * 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
96       * lowest value is in queue[0], assuming the queue is nonempty.       * lowest value is in queue[0], assuming the queue is nonempty.
97       */       */
98      private transient Object[] queue;      transient Object[] queue; // non-private to simplify nested class access
99    
100      /**      /**
101       * The number of elements in the priority queue.       * The number of elements in the priority queue.
# Line 91  Line 112 
112       * The number of times this priority queue has been       * The number of times this priority queue has been
113       * <i>structurally modified</i>.  See AbstractList for gory details.       * <i>structurally modified</i>.  See AbstractList for gory details.
114       */       */
115      private transient int modCount = 0;      transient int modCount = 0; // non-private to simplify nested class access
116    
117      /**      /**
118       * Creates a <tt>PriorityQueue</tt> with the default initial       * Creates a {@code PriorityQueue} with the default initial
119       * capacity (11) that orders its elements according to their       * capacity (11) that orders its elements according to their
120       * {@linkplain Comparable natural ordering}.       * {@linkplain Comparable natural ordering}.
121       */       */
# Line 103  Line 124 
124      }      }
125    
126      /**      /**
127       * Creates a <tt>PriorityQueue</tt> with the specified initial       * Creates a {@code PriorityQueue} with the specified initial
128       * capacity that orders its elements according to their       * capacity that orders its elements according to their
129       * {@linkplain Comparable natural ordering}.       * {@linkplain Comparable natural ordering}.
130       *       *
131       * @param initialCapacity the initial capacity for this priority queue       * @param initialCapacity the initial capacity for this priority queue
132       * @throws IllegalArgumentException if <tt>initialCapacity</tt> is less       * @throws IllegalArgumentException if {@code initialCapacity} is less
133       * than 1       * than 1
134       */       */
135      public PriorityQueue(int initialCapacity) {      public PriorityQueue(int initialCapacity) {
# Line 116  Line 137 
137      }      }
138    
139      /**      /**
140       * Creates a <tt>PriorityQueue</tt> with the specified initial capacity       * Creates a {@code PriorityQueue} with the specified initial capacity
141       * that orders its elements according to the specified comparator.       * that orders its elements according to the specified comparator.
142       *       *
143       * @param  initialCapacity the initial capacity for this priority queue       * @param  initialCapacity the initial capacity for this priority queue
144       * @param  comparator the comparator that will be used to order       * @param  comparator the comparator that will be used to order this
145       *         this priority queue.  If <tt>null</tt>, the <i>natural       *         priority queue.  If {@code null}, the {@linkplain Comparable
146       *         ordering</i> of the elements will be used.       *         natural ordering} of the elements will be used.
147       * @throws IllegalArgumentException if <tt>initialCapacity</tt> is       * @throws IllegalArgumentException if {@code initialCapacity} is
148       *         less than 1       *         less than 1
149       */       */
150      public PriorityQueue(int initialCapacity,      public PriorityQueue(int initialCapacity,
# Line 137  Line 158 
158      }      }
159    
160      /**      /**
161       * Creates a <tt>PriorityQueue</tt> containing the elements in the       * Creates a {@code PriorityQueue} containing the elements in the
162       * specified collection.   If the specified collection is an       * specified collection.  If the specified collection is an instance of
163       * instance of a {@link java.util.SortedSet} or is another       * a {@link SortedSet} or is another {@code PriorityQueue}, this
164       * <tt>PriorityQueue</tt>, the priority queue will be ordered       * priority queue will be ordered according to the same ordering.
165       * according to the same ordering.  Otherwise, this priority queue       * Otherwise, this priority queue will be ordered according to the
166       * will be ordered according to the natural ordering of its elements.       * {@linkplain Comparable natural ordering} of its elements.
167       *       *
168       * @param  c the collection whose elements are to be placed       * @param  c the collection whose elements are to be placed
169       *         into this priority queue       *         into this priority queue
# Line 152  Line 173 
173       * @throws NullPointerException if the specified collection or any       * @throws NullPointerException if the specified collection or any
174       *         of its elements are null       *         of its elements are null
175       */       */
176        @SuppressWarnings("unchecked")
177      public PriorityQueue(Collection<? extends E> c) {      public PriorityQueue(Collection<? extends E> c) {
178          initFromCollection(c);          if (c instanceof SortedSet<?>) {
179          if (c instanceof SortedSet)              SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
180              comparator = (Comparator<? super E>)              this.comparator = (Comparator<? super E>) ss.comparator();
181                  ((SortedSet<? extends E>)c).comparator();              initElementsFromCollection(ss);
182          else if (c instanceof PriorityQueue)          }
183              comparator = (Comparator<? super E>)          else if (c instanceof PriorityQueue<?>) {
184                  ((PriorityQueue<? extends E>)c).comparator();              PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
185                this.comparator = (Comparator<? super E>) pq.comparator();
186                initFromPriorityQueue(pq);
187            }
188          else {          else {
189              comparator = null;              this.comparator = null;
190              heapify();              initFromCollection(c);
191          }          }
192      }      }
193    
194      /**      /**
195       * Creates a <tt>PriorityQueue</tt> containing the elements in the       * Creates a {@code PriorityQueue} containing the elements in the
196       * specified priority queue.  This priority queue will be       * specified priority queue.  This priority queue will be
197       * ordered according to the same ordering as the given priority       * ordered according to the same ordering as the given priority
198       * queue.       * queue.
199       *       *
200       * @param  c the priority queue whose elements are to be placed       * @param  c the priority queue whose elements are to be placed
201       *         into this priority queue       *         into this priority queue
202       * @throws ClassCastException if elements of <tt>c</tt> cannot be       * @throws ClassCastException if elements of {@code c} cannot be
203       *         compared to one another according to <tt>c</tt>'s       *         compared to one another according to {@code c}'s
204       *         ordering       *         ordering
205       * @throws NullPointerException if the specified priority queue or any       * @throws NullPointerException if the specified priority queue or any
206       *         of its elements are null       *         of its elements are null
207       */       */
208        @SuppressWarnings("unchecked")
209      public PriorityQueue(PriorityQueue<? extends E> c) {      public PriorityQueue(PriorityQueue<? extends E> c) {
210          comparator = (Comparator<? super E>)c.comparator();          this.comparator = (Comparator<? super E>) c.comparator();
211          initFromCollection(c);          initFromPriorityQueue(c);
212      }      }
213    
214      /**      /**
215       * Creates a <tt>PriorityQueue</tt> containing the elements in the       * Creates a {@code PriorityQueue} containing the elements in the
216       * specified sorted set.  This priority queue will be ordered       * specified sorted set.  This priority queue will be ordered
217       * according to the same ordering as the given sorted set.       * according to the same ordering as the given sorted set.
218       *       *
219       * @param  c the sorted set whose elements are to be placed       * @param  c the sorted set whose elements are to be placed
220       *         into this priority queue.       *         into this priority queue
221       * @throws ClassCastException if elements of the specified sorted       * @throws ClassCastException if elements of the specified sorted
222       *         set cannot be compared to one another according to the       *         set cannot be compared to one another according to the
223       *         sorted set's ordering       *         sorted set's ordering
224       * @throws NullPointerException if the specified sorted set or any       * @throws NullPointerException if the specified sorted set or any
225       *         of its elements are null       *         of its elements are null
226       */       */
227        @SuppressWarnings("unchecked")
228      public PriorityQueue(SortedSet<? extends E> c) {      public PriorityQueue(SortedSet<? extends E> c) {
229          comparator = (Comparator<? super E>)c.comparator();          this.comparator = (Comparator<? super E>) c.comparator();
230            initElementsFromCollection(c);
231        }
232    
233        private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
234            if (c.getClass() == PriorityQueue.class) {
235                this.queue = c.toArray();
236                this.size = c.size();
237            } else {
238          initFromCollection(c);          initFromCollection(c);
239      }      }
240        }
241    
242      /**      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) {  
243          Object[] a = c.toArray();          Object[] a = c.toArray();
244          // If c.toArray incorrectly doesn't return Object[], copy it.          // If c.toArray incorrectly doesn't return Object[], copy it.
245          if (a.getClass() != Object[].class)          if (a.getClass() != Object[].class)
246              a = Arrays.copyOf(a, a.length, Object[].class);              a = Arrays.copyOf(a, a.length, Object[].class);
247          queue = a;          int len = a.length;
248          size = a.length;          if (len == 1 || this.comparator != null)
249                for (int i = 0; i < len; i++)
250                    if (a[i] == null)
251                        throw new NullPointerException();
252            this.queue = a;
253            this.size = a.length;
254      }      }
255    
256      /**      /**
257         * Initializes queue array with elements from the given Collection.
258         *
259         * @param c the collection
260         */
261        private void initFromCollection(Collection<? extends E> c) {
262            initElementsFromCollection(c);
263            heapify();
264        }
265    
266        /**
267         * The maximum size of array to allocate.
268         * Some VMs reserve some header words in an array.
269         * Attempts to allocate larger arrays may result in
270         * OutOfMemoryError: Requested array size exceeds VM limit
271         */
272        private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
273    
274        /**
275       * Increases the capacity of the array.       * Increases the capacity of the array.
276       *       *
277       * @param minCapacity the desired minimum capacity       * @param minCapacity the desired minimum capacity
278       */       */
279      private void grow(int minCapacity) {      private void grow(int minCapacity) {
         if (minCapacity < 0) // overflow  
             throw new OutOfMemoryError();  
280          int oldCapacity = queue.length;          int oldCapacity = queue.length;
281          // Double size if small; else grow by 50%          // Double size if small; else grow by 50%
282          int newCapacity = ((oldCapacity < 64)?          int newCapacity = oldCapacity + ((oldCapacity < 64) ?
283                             ((oldCapacity + 1) * 2):                                           (oldCapacity + 2) :
284                             ((oldCapacity / 2) * 3));                                           (oldCapacity >> 1));
285          if (newCapacity < 0) // overflow          // overflow-conscious code
286              newCapacity = Integer.MAX_VALUE;          if (newCapacity - MAX_ARRAY_SIZE > 0)
287          if (newCapacity < minCapacity)              newCapacity = hugeCapacity(minCapacity);
             newCapacity = minCapacity;  
288          queue = Arrays.copyOf(queue, newCapacity);          queue = Arrays.copyOf(queue, newCapacity);
289      }      }
290    
291        private static int hugeCapacity(int minCapacity) {
292            if (minCapacity < 0) // overflow
293                throw new OutOfMemoryError();
294            return (minCapacity > MAX_ARRAY_SIZE) ?
295                Integer.MAX_VALUE :
296                MAX_ARRAY_SIZE;
297        }
298    
299      /**      /**
300       * Inserts the specified element into this priority queue.       * Inserts the specified element into this priority queue.
301       *       *
302       * @return <tt>true</tt> (as specified by {@link Collection#add})       * @return {@code true} (as specified by {@link Collection#add})
303       * @throws ClassCastException if the specified element cannot be       * @throws ClassCastException if the specified element cannot be
304       *         compared with elements currently in this priority queue       *         compared with elements currently in this priority queue
305       *         according to the priority queue's ordering       *         according to the priority queue's ordering
# Line 252  Line 312 
312      /**      /**
313       * Inserts the specified element into this priority queue.       * Inserts the specified element into this priority queue.
314       *       *
315       * @return <tt>true</tt> (as specified by {@link Queue#offer})       * @return {@code true} (as specified by {@link Queue#offer})
316       * @throws ClassCastException if the specified element cannot be       * @throws ClassCastException if the specified element cannot be
317       *         compared with elements currently in this priority queue       *         compared with elements currently in this priority queue
318       *         according to the priority queue's ordering       *         according to the priority queue's ordering
# Line 273  Line 333 
333          return true;          return true;
334      }      }
335    
336        @SuppressWarnings("unchecked")
337      public E peek() {      public E peek() {
338          if (size == 0)          return (size == 0) ? null : (E) queue[0];
             return null;  
         return (E) queue[0];  
339      }      }
340    
341      private int indexOf(Object o) {      private int indexOf(Object o) {
# Line 290  Line 349 
349    
350      /**      /**
351       * Removes a single instance of the specified element from this queue,       * Removes a single instance of the specified element from this queue,
352       * 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
353       * 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
354       * elements.  Returns true if this queue contained the specified element       * elements.  Returns {@code true} if and only if this queue contained
355       * (or equivalently, if this queue changed as a result of the call).       * the specified element (or equivalently, if this queue changed as a
356         * result of the call).
357       *       *
358       * @param o element to be removed from this queue, if present       * @param o element to be removed from this queue, if present
359       * @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
360       */       */
361      public boolean remove(Object o) {      public boolean remove(Object o) {
362          int i = indexOf(o);          int i = indexOf(o);
# Line 313  Line 373 
373       * Needed by iterator.remove.       * Needed by iterator.remove.
374       *       *
375       * @param o element to be removed from this queue, if present       * @param o element to be removed from this queue, if present
376       * @return <tt>true</tt> if removed       * @return {@code true} if removed
377       */       */
378      boolean removeEq(Object o) {      boolean removeEq(Object o) {
379          for (int i = 0; i < size; i++) {          for (int i = 0; i < size; i++) {
# Line 326  Line 386 
386      }      }
387    
388      /**      /**
389       * Returns <tt>true</tt> if this queue contains the specified element.       * Returns {@code true} if this queue contains the specified element.
390       * 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
391       * 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)}.
392       *       *
393       * @param o object to be checked for containment in this queue       * @param o object to be checked for containment in this queue
394       * @return <tt>true</tt> if this queue contains the specified element       * @return {@code true} if this queue contains the specified element
395       */       */
396      public boolean contains(Object o) {      public boolean contains(Object o) {
397          return indexOf(o) != -1;          return indexOf(o) != -1;
398      }      }
399    
400      /**      /**
401       * Returns an array containing all of the elements in this queue,       * Returns an array containing all of the elements in this queue.
402       * The elements are in no particular order.       * The elements are in no particular order.
403       *       *
404       * <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
405       * maintained by this list.  (In other words, this method must allocate       * maintained by this queue.  (In other words, this method must allocate
406       * 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.
407       *       *
408         * <p>This method acts as bridge between array-based and collection-based
409         * APIs.
410         *
411       * @return an array containing all of the elements in this queue       * @return an array containing all of the elements in this queue
412       */       */
413      public Object[] toArray() {      public Object[] toArray() {
# Line 352  Line 415 
415      }      }
416    
417      /**      /**
418       * Returns an array containing all of the elements in this queue.       * Returns an array containing all of the elements in this queue; the
419       * The elements are in no particular order.  The runtime type of       * runtime type of the returned array is that of the specified array.
420       * the returned array is that of the specified array.  If the queue       * The returned array elements are in no particular order.
421       * fits in the specified array, it is returned therein.       * If the queue fits in the specified array, it is returned therein.
422       * Otherwise, a new array is allocated with the runtime type of       * Otherwise, a new array is allocated with the runtime type of the
423       * the specified array and the size of this queue.       * specified array and the size of this queue.
424       *       *
425       * <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
426       * (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
427       * the array immediately following the end of the collection is set to       * the array immediately following the end of the collection is set to
428       * <tt>null</tt>.  (This is useful in determining the length of the       * {@code null}.
429       * queue <i>only</i> if the caller knows that the queue does not contain       *
430       * any null elements.)       * <p>Like the {@link #toArray()} method, this method acts as bridge between
431         * array-based and collection-based APIs.  Further, this method allows
432         * precise control over the runtime type of the output array, and may,
433         * under certain circumstances, be used to save allocation costs.
434         *
435         * <p>Suppose {@code x} is a queue known to contain only strings.
436         * The following code can be used to dump the queue into a newly
437         * allocated array of {@code String}:
438         *
439         *  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
440         *
441         * Note that {@code toArray(new Object[0])} is identical in function to
442         * {@code toArray()}.
443       *       *
444       * @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
445       *          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
446       *          same runtime type is allocated for this purpose.       *          same runtime type is allocated for this purpose.
447       * @return an array containing the elements of the queue       * @return an array containing all of the elements in this queue
448       * @throws ArrayStoreException if the runtime type of the specified array       * @throws ArrayStoreException if the runtime type of the specified array
449       *         is not a supertype of the runtime type of every element in       *         is not a supertype of the runtime type of every element in
450       *         this queue       *         this queue
451       * @throws NullPointerException if the specified array is null       * @throws NullPointerException if the specified array is null
452       */       */
453        @SuppressWarnings("unchecked")
454      public <T> T[] toArray(T[] a) {      public <T> T[] toArray(T[] a) {
455            final int size = this.size;
456          if (a.length < size)          if (a.length < size)
457              // Make a new array of a's runtime type, but my contents:              // Make a new array of a's runtime type, but my contents:
458              return (T[]) Arrays.copyOf(queue, size, a.getClass());              return (T[]) Arrays.copyOf(queue, size, a.getClass());
# Line 418  Line 495 
495           * after we've completed the "normal" iteration.           * after we've completed the "normal" iteration.
496           *           *
497           * We expect that most iterations, even those involving removals,           * We expect that most iterations, even those involving removals,
498           * will not use need to store elements in this field.           * will not need to store elements in this field.
499           */           */
500          private ArrayDeque<E> forgetMeNot = null;          private ArrayDeque<E> forgetMeNot = null;
501    
# Line 430  Line 507 
507    
508          /**          /**
509           * The modCount value that the iterator believes that the backing           * The modCount value that the iterator believes that the backing
510           * List should have.  If this expectation is violated, the iterator           * Queue should have.  If this expectation is violated, the iterator
511           * has detected concurrent modification.           * has detected concurrent modification.
512           */           */
513          private int expectedModCount = modCount;          private int expectedModCount = modCount;
# Line 440  Line 517 
517                  (forgetMeNot != null && !forgetMeNot.isEmpty());                  (forgetMeNot != null && !forgetMeNot.isEmpty());
518          }          }
519    
520            @SuppressWarnings("unchecked")
521          public E next() {          public E next() {
522              if (expectedModCount != modCount)              if (expectedModCount != modCount)
523                  throw new ConcurrentModificationException();                  throw new ConcurrentModificationException();
# Line 457  Line 535 
535          public void remove() {          public void remove() {
536              if (expectedModCount != modCount)              if (expectedModCount != modCount)
537                  throw new ConcurrentModificationException();                  throw new ConcurrentModificationException();
             if (lastRet == -1 && lastRetElt == null)  
                 throw new IllegalStateException();  
538              if (lastRet != -1) {              if (lastRet != -1) {
539                  E moved = PriorityQueue.this.removeAt(lastRet);                  E moved = PriorityQueue.this.removeAt(lastRet);
540                  lastRet = -1;                  lastRet = -1;
# Line 466  Line 542 
542                      cursor--;                      cursor--;
543                  else {                  else {
544                      if (forgetMeNot == null)                      if (forgetMeNot == null)
545                          forgetMeNot = new ArrayDeque<E>();                          forgetMeNot = new ArrayDeque<>();
546                      forgetMeNot.add(moved);                      forgetMeNot.add(moved);
547                  }                  }
548              } else {              } else if (lastRetElt != null) {
549                  PriorityQueue.this.removeEq(lastRetElt);                  PriorityQueue.this.removeEq(lastRetElt);
550                  lastRetElt = null;                  lastRetElt = null;
551                } else {
552                    throw new IllegalStateException();
553              }              }
554              expectedModCount = modCount;              expectedModCount = modCount;
555          }          }
   
556      }      }
557    
558      public int size() {      public int size() {
# Line 493  Line 570 
570          size = 0;          size = 0;
571      }      }
572    
573        @SuppressWarnings("unchecked")
574      public E poll() {      public E poll() {
575          if (size == 0)          if (size == 0)
576              return null;              return null;
# Line 516  Line 594 
594       * i.  Under these circumstances, this method returns the element       * i.  Under these circumstances, this method returns the element
595       * 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
596       * 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
597       * avoid missing traverseing elements.       * avoid missing traversing elements.
598       */       */
599        @SuppressWarnings("unchecked")
600      private E removeAt(int i) {      private E removeAt(int i) {
601          assert i >= 0 && i < size;          // assert i >= 0 && i < size;
602          modCount++;          modCount++;
603          int s = --size;          int s = --size;
604          if (s == i) // removed last element          if (s == i) // removed last element
# Line 556  Line 635 
635              siftUpComparable(k, x);              siftUpComparable(k, x);
636      }      }
637    
638        @SuppressWarnings("unchecked")
639      private void siftUpComparable(int k, E x) {      private void siftUpComparable(int k, E x) {
640          Comparable<? super E> key = (Comparable<? super E>) x;          Comparable<? super E> key = (Comparable<? super E>) x;
641          while (k > 0) {          while (k > 0) {
# Line 569  Line 649 
649          queue[k] = key;          queue[k] = key;
650      }      }
651    
652        @SuppressWarnings("unchecked")
653      private void siftUpUsingComparator(int k, E x) {      private void siftUpUsingComparator(int k, E x) {
654          while (k > 0) {          while (k > 0) {
655              int parent = (k - 1) >>> 1;              int parent = (k - 1) >>> 1;
# Line 596  Line 677 
677              siftDownComparable(k, x);              siftDownComparable(k, x);
678      }      }
679    
680        @SuppressWarnings("unchecked")
681      private void siftDownComparable(int k, E x) {      private void siftDownComparable(int k, E x) {
682          Comparable<? super E> key = (Comparable<? super E>)x;          Comparable<? super E> key = (Comparable<? super E>)x;
683          int half = size >>> 1;        // loop while a non-leaf          int half = size >>> 1;        // loop while a non-leaf
# Line 614  Line 696 
696          queue[k] = key;          queue[k] = key;
697      }      }
698    
699        @SuppressWarnings("unchecked")
700      private void siftDownUsingComparator(int k, E x) {      private void siftDownUsingComparator(int k, E x) {
701          int half = size >>> 1;          int half = size >>> 1;
702          while (k < half) {          while (k < half) {
# Line 635  Line 718 
718       * Establishes the heap invariant (described above) in the entire tree,       * Establishes the heap invariant (described above) in the entire tree,
719       * assuming nothing about the order of the elements prior to the call.       * assuming nothing about the order of the elements prior to the call.
720       */       */
721        @SuppressWarnings("unchecked")
722      private void heapify() {      private void heapify() {
723          for (int i = (size >>> 1) - 1; i >= 0; i--)          for (int i = (size >>> 1) - 1; i >= 0; i--)
724              siftDown(i, (E)queue[i]);              siftDown(i, (E)queue[i]);
# Line 642  Line 726 
726    
727      /**      /**
728       * Returns the comparator used to order the elements in this       * Returns the comparator used to order the elements in this
729       * queue, or <tt>null</tt> if this queue is sorted according to       * queue, or {@code null} if this queue is sorted according to
730       * the {@linkplain Comparable natural ordering} of its elements.       * the {@linkplain Comparable natural ordering} of its elements.
731       *       *
732       * @return the comparator used to order this queue, or       * @return the comparator used to order this queue, or
733       *         <tt>null</tt> if this queue is sorted according to the       *         {@code null} if this queue is sorted according to the
734       *         natural ordering of its elements.       *         natural ordering of its elements
735       */       */
736      public Comparator<? super E> comparator() {      public Comparator<? super E> comparator() {
737          return comparator;          return comparator;
738      }      }
739    
740      /**      /**
741       * Save the state of the instance to a stream (that       * Saves this queue to a stream (that is, serializes it).
      * is, serialize it).  
742       *       *
743       * @serialData The length of the array backing the instance is       * @serialData The length of the array backing the instance is
744       * emitted (int), followed by all of its elements (each an       *             emitted (int), followed by all of its elements
745       * <tt>Object</tt>) in the proper order.       *             (each an {@code Object}) in the proper order.
746       * @param s the stream       * @param s the stream
747       */       */
748      private void writeObject(java.io.ObjectOutputStream s)      private void writeObject(java.io.ObjectOutputStream s)
# Line 667  Line 750 
750          // Write out element count, and any hidden stuff          // Write out element count, and any hidden stuff
751          s.defaultWriteObject();          s.defaultWriteObject();
752    
753          // Write out array length          // Write out array length, for compatibility with 1.5 version
754          // 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));  
755    
756          // Write out all elements in the proper order.          // Write out all elements in the "proper order".
757          for (int i=0; i<size; i++)          for (int i=0; i<size; i++)
758              s.writeObject(queue[i]);              s.writeObject(queue[i]);
759      }      }
760    
761      /**      /**
762       * Reconstitute the <tt>PriorityQueue</tt> instance from a stream       * Reconstitutes the {@code PriorityQueue} instance from a stream
763       * (that is, deserialize it).       * (that is, deserializes it).
764         *
765       * @param s the stream       * @param s the stream
766       */       */
767      private void readObject(java.io.ObjectInputStream s)      private void readObject(java.io.ObjectInputStream s)
# Line 686  Line 769 
769          // Read in size, and any hidden stuff          // Read in size, and any hidden stuff
770          s.defaultReadObject();          s.defaultReadObject();
771    
772          // Read in array length and allocate array          // Read in (and discard) array length
773          int arrayLength = s.readInt();          s.readInt();
         queue = new Object[arrayLength];  
774    
775          // Read in all elements in the proper order.          queue = new Object[size];
776    
777            // Read in all elements.
778          for (int i=0; i<size; i++)          for (int i=0; i<size; i++)
779              queue[i] = (E) s.readObject();              queue[i] = s.readObject();
780    
781            // Elements are guaranteed to be in "proper order", but the
782            // spec has never explained what that might be.
783            heapify();
784        }
785    
786        final Spliterator<E> spliterator() {
787            return new PriorityQueueSpliterator<E>(this, 0, -1, 0);
788        }
789    
790        public Stream<E> stream() {
791            return Streams.stream(spliterator());
792        }
793    
794        public Stream<E> parallelStream() {
795            return Streams.parallelStream(spliterator());
796        }
797    
798        static final class PriorityQueueSpliterator<E> implements Spliterator<E> {
799            /*
800             * This is very similar to ArrayList Spliterator, except for
801             * extra null checks.
802             */
803            private final PriorityQueue<E> pq;
804            private int index;            // current index, modified on advance/split
805            private int fence;            // -1 until first use
806            private int expectedModCount; // initialized when fence set
807    
808            /** Create new spliterator covering the given  range */
809            PriorityQueueSpliterator(PriorityQueue<E> pq, int origin, int fence,
810                                 int expectedModCount) {
811                this.pq = pq;
812                this.index = origin;
813                this.fence = fence;
814                this.expectedModCount = expectedModCount;
815            }
816    
817            private int getFence() { // initialize fence to size on first use
818                int hi;
819                if ((hi = fence) < 0) {
820                    expectedModCount = pq.modCount;
821                    hi = fence = pq.size;
822                }
823                return hi;
824            }
825    
826            public PriorityQueueSpliterator<E> trySplit() {
827                int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
828                return (lo >= mid) ? null :
829                    new PriorityQueueSpliterator<E>(pq, lo, index = mid,
830                                                    expectedModCount);
831            }
832    
833            @SuppressWarnings("unchecked")
834            public void forEach(Consumer<? super E> action) {
835                int i, hi, mc; // hoist accesses and checks from loop
836                PriorityQueue<E> q; Object[] a;
837                if (action == null)
838                    throw new NullPointerException();
839                if ((q = pq) != null && (a = q.queue) != null) {
840                    if ((hi = fence) < 0) {
841                        mc = q.modCount;
842                        hi = q.size;
843                    }
844                    else
845                        mc = expectedModCount;
846                    if ((i = index) >= 0 && (index = hi) <= a.length) {
847                        for (E e;; ++i) {
848                            if (i < hi) {
849                                if ((e = (E) a[i]) == null) // must be CME
850                                    break;
851                                action.accept(e);
852                            }
853                            else if (q.modCount != mc)
854                                break;
855                            else
856                                return;
857                        }
858                    }
859                }
860                throw new ConcurrentModificationException();
861      }      }
862    
863            public boolean tryAdvance(Consumer<? super E> action) {
864                int hi = getFence(), lo = index;
865                if (lo >= 0 && lo < hi) {
866                    index = lo + 1;
867                    @SuppressWarnings("unchecked") E e = (E)pq.queue[lo];
868                    if (e == null)
869                        throw new ConcurrentModificationException();
870                    action.accept(e);
871                    if (pq.modCount != expectedModCount)
872                        throw new ConcurrentModificationException();
873                    return true;
874                }
875                return false;
876            }
877    
878            public long estimateSize() {
879                return (long) (getFence() - index);
880            }
881    
882            public int characteristics() {
883                return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;
884            }
885        }
886  }  }

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