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revision 1.66, Sun Jan 7 07:38:27 2007 UTC revision 1.96, Thu May 2 06:02:17 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 2007 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    
30  /**  /**
31   * An unbounded priority {@linkplain Queue queue} based on a priority heap.   * An unbounded priority {@linkplain Queue queue} based on a priority heap.
# Line 56  Line 76 
76   * Java Collections Framework</a>.   * Java Collections Framework</a>.
77   *   *
78   * @since 1.5   * @since 1.5
  * @version %I%, %G%  
79   * @author Josh Bloch, Doug Lea   * @author Josh Bloch, Doug Lea
80   * @param <E> the type of elements held in this collection   * @param <E> the type of elements held in this collection
81   */   */
# Line 75  Line 94 
94       * 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
95       * lowest value is in queue[0], assuming the queue is nonempty.       * lowest value is in queue[0], assuming the queue is nonempty.
96       */       */
97      private transient Object[] queue;      transient Object[] queue; // non-private to simplify nested class access
98    
99      /**      /**
100       * The number of elements in the priority queue.       * The number of elements in the priority queue.
# Line 92  Line 111 
111       * The number of times this priority queue has been       * The number of times this priority queue has been
112       * <i>structurally modified</i>.  See AbstractList for gory details.       * <i>structurally modified</i>.  See AbstractList for gory details.
113       */       */
114      private transient int modCount = 0;      transient int modCount = 0; // non-private to simplify nested class access
115    
116      /**      /**
117       * Creates a {@code PriorityQueue} with the default initial       * Creates a {@code PriorityQueue} with the default initial
# Line 153  Line 172 
172       * @throws NullPointerException if the specified collection or any       * @throws NullPointerException if the specified collection or any
173       *         of its elements are null       *         of its elements are null
174       */       */
175        @SuppressWarnings("unchecked")
176      public PriorityQueue(Collection<? extends E> c) {      public PriorityQueue(Collection<? extends E> c) {
177          initFromCollection(c);          if (c instanceof SortedSet<?>) {
178          if (c instanceof SortedSet)              SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
179              comparator = (Comparator<? super E>)              this.comparator = (Comparator<? super E>) ss.comparator();
180                  ((SortedSet<? extends E>)c).comparator();              initElementsFromCollection(ss);
181          else if (c instanceof PriorityQueue)          }
182              comparator = (Comparator<? super E>)          else if (c instanceof PriorityQueue<?>) {
183                  ((PriorityQueue<? extends E>)c).comparator();              PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
184                this.comparator = (Comparator<? super E>) pq.comparator();
185                initFromPriorityQueue(pq);
186            }
187          else {          else {
188              comparator = null;              this.comparator = null;
189              heapify();              initFromCollection(c);
190          }          }
191      }      }
192    
# Line 181  Line 204 
204       * @throws NullPointerException if the specified priority queue or any       * @throws NullPointerException if the specified priority queue or any
205       *         of its elements are null       *         of its elements are null
206       */       */
207        @SuppressWarnings("unchecked")
208      public PriorityQueue(PriorityQueue<? extends E> c) {      public PriorityQueue(PriorityQueue<? extends E> c) {
209          comparator = (Comparator<? super E>)c.comparator();          this.comparator = (Comparator<? super E>) c.comparator();
210          initFromCollection(c);          initFromPriorityQueue(c);
211      }      }
212    
213      /**      /**
# Line 199  Line 223 
223       * @throws NullPointerException if the specified sorted set or any       * @throws NullPointerException if the specified sorted set or any
224       *         of its elements are null       *         of its elements are null
225       */       */
226        @SuppressWarnings("unchecked")
227      public PriorityQueue(SortedSet<? extends E> c) {      public PriorityQueue(SortedSet<? extends E> c) {
228          comparator = (Comparator<? super E>)c.comparator();          this.comparator = (Comparator<? super E>) c.comparator();
229            initElementsFromCollection(c);
230        }
231    
232        private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
233            if (c.getClass() == PriorityQueue.class) {
234                this.queue = c.toArray();
235                this.size = c.size();
236            } else {
237          initFromCollection(c);          initFromCollection(c);
238      }      }
239        }
240    
241        private void initElementsFromCollection(Collection<? extends E> c) {
242            Object[] a = c.toArray();
243            // If c.toArray incorrectly doesn't return Object[], copy it.
244            if (a.getClass() != Object[].class)
245                a = Arrays.copyOf(a, a.length, Object[].class);
246            int len = a.length;
247            if (len == 1 || this.comparator != null)
248                for (int i = 0; i < len; i++)
249                    if (a[i] == null)
250                        throw new NullPointerException();
251            this.queue = a;
252            this.size = a.length;
253        }
254    
255      /**      /**
256       * Initializes queue array with elements from the given Collection.       * Initializes queue array with elements from the given Collection.
# Line 210  Line 258 
258       * @param c the collection       * @param c the collection
259       */       */
260      private void initFromCollection(Collection<? extends E> c) {      private void initFromCollection(Collection<? extends E> c) {
261          Object[] a = c.toArray();          initElementsFromCollection(c);
262          // If c.toArray incorrectly doesn't return Object[], copy it.          heapify();
         if (a.getClass() != Object[].class)  
             a = Arrays.copyOf(a, a.length, Object[].class);  
         queue = a;  
         size = a.length;  
263      }      }
264    
265      /**      /**
266         * The maximum size of array to allocate.
267         * Some VMs reserve some header words in an array.
268         * Attempts to allocate larger arrays may result in
269         * OutOfMemoryError: Requested array size exceeds VM limit
270         */
271        private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
272    
273        /**
274       * Increases the capacity of the array.       * Increases the capacity of the array.
275       *       *
276       * @param minCapacity the desired minimum capacity       * @param minCapacity the desired minimum capacity
277       */       */
278      private void grow(int minCapacity) {      private void grow(int minCapacity) {
         if (minCapacity < 0) // overflow  
             throw new OutOfMemoryError();  
279          int oldCapacity = queue.length;          int oldCapacity = queue.length;
280          // Double size if small; else grow by 50%          // Double size if small; else grow by 50%
281          int newCapacity = ((oldCapacity < 64)?          int newCapacity = oldCapacity + ((oldCapacity < 64) ?
282                             ((oldCapacity + 1) * 2):                                           (oldCapacity + 2) :
283                             ((oldCapacity / 2) * 3));                                           (oldCapacity >> 1));
284          if (newCapacity < 0) // overflow          // overflow-conscious code
285              newCapacity = Integer.MAX_VALUE;          if (newCapacity - MAX_ARRAY_SIZE > 0)
286          if (newCapacity < minCapacity)              newCapacity = hugeCapacity(minCapacity);
             newCapacity = minCapacity;  
287          queue = Arrays.copyOf(queue, newCapacity);          queue = Arrays.copyOf(queue, newCapacity);
288      }      }
289    
290        private static int hugeCapacity(int minCapacity) {
291            if (minCapacity < 0) // overflow
292                throw new OutOfMemoryError();
293            return (minCapacity > MAX_ARRAY_SIZE) ?
294                Integer.MAX_VALUE :
295                MAX_ARRAY_SIZE;
296        }
297    
298      /**      /**
299       * Inserts the specified element into this priority queue.       * Inserts the specified element into this priority queue.
300       *       *
# Line 275  Line 332 
332          return true;          return true;
333      }      }
334    
335        @SuppressWarnings("unchecked")
336      public E peek() {      public E peek() {
337          if (size == 0)          return (size == 0) ? null : (E) queue[0];
             return null;  
         return (E) queue[0];  
338      }      }
339    
340      private int indexOf(Object o) {      private int indexOf(Object o) {
# Line 375  Line 431 
431       * precise control over the runtime type of the output array, and may,       * precise control over the runtime type of the output array, and may,
432       * under certain circumstances, be used to save allocation costs.       * under certain circumstances, be used to save allocation costs.
433       *       *
434       * <p>Suppose <tt>x</tt> is a queue known to contain only strings.       * <p>Suppose {@code x} is a queue known to contain only strings.
435       * The following code can be used to dump the queue into a newly       * The following code can be used to dump the queue into a newly
436       * allocated array of <tt>String</tt>:       * allocated array of {@code String}:
437       *       *
438       * <pre>       *  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
      *     String[] y = x.toArray(new String[0]);</pre>  
439       *       *
440       * Note that <tt>toArray(new Object[0])</tt> is identical in function to       * Note that {@code toArray(new Object[0])} is identical in function to
441       * <tt>toArray()</tt>.       * {@code toArray()}.
442       *       *
443       * @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
444       *          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
# Line 394  Line 449 
449       *         this queue       *         this queue
450       * @throws NullPointerException if the specified array is null       * @throws NullPointerException if the specified array is null
451       */       */
452        @SuppressWarnings("unchecked")
453      public <T> T[] toArray(T[] a) {      public <T> T[] toArray(T[] a) {
454            final int size = this.size;
455          if (a.length < size)          if (a.length < size)
456              // Make a new array of a's runtime type, but my contents:              // Make a new array of a's runtime type, but my contents:
457              return (T[]) Arrays.copyOf(queue, size, a.getClass());              return (T[]) Arrays.copyOf(queue, size, a.getClass());
# Line 459  Line 516 
516                  (forgetMeNot != null && !forgetMeNot.isEmpty());                  (forgetMeNot != null && !forgetMeNot.isEmpty());
517          }          }
518    
519            @SuppressWarnings("unchecked")
520          public E next() {          public E next() {
521              if (expectedModCount != modCount)              if (expectedModCount != modCount)
522                  throw new ConcurrentModificationException();                  throw new ConcurrentModificationException();
# Line 483  Line 541 
541                      cursor--;                      cursor--;
542                  else {                  else {
543                      if (forgetMeNot == null)                      if (forgetMeNot == null)
544                          forgetMeNot = new ArrayDeque<E>();                          forgetMeNot = new ArrayDeque<>();
545                      forgetMeNot.add(moved);                      forgetMeNot.add(moved);
546                  }                  }
547              } else if (lastRetElt != null) {              } else if (lastRetElt != null) {
# Line 511  Line 569 
569          size = 0;          size = 0;
570      }      }
571    
572        @SuppressWarnings("unchecked")
573      public E poll() {      public E poll() {
574          if (size == 0)          if (size == 0)
575              return null;              return null;
# Line 536  Line 595 
595       * 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
596       * avoid missing traversing elements.       * avoid missing traversing elements.
597       */       */
598        @SuppressWarnings("unchecked")
599      private E removeAt(int i) {      private E removeAt(int i) {
600          assert i >= 0 && i < size;          // assert i >= 0 && i < size;
601          modCount++;          modCount++;
602          int s = --size;          int s = --size;
603          if (s == i) // removed last element          if (s == i) // removed last element
# Line 574  Line 634 
634              siftUpComparable(k, x);              siftUpComparable(k, x);
635      }      }
636    
637        @SuppressWarnings("unchecked")
638      private void siftUpComparable(int k, E x) {      private void siftUpComparable(int k, E x) {
639          Comparable<? super E> key = (Comparable<? super E>) x;          Comparable<? super E> key = (Comparable<? super E>) x;
640          while (k > 0) {          while (k > 0) {
# Line 587  Line 648 
648          queue[k] = key;          queue[k] = key;
649      }      }
650    
651        @SuppressWarnings("unchecked")
652      private void siftUpUsingComparator(int k, E x) {      private void siftUpUsingComparator(int k, E x) {
653          while (k > 0) {          while (k > 0) {
654              int parent = (k - 1) >>> 1;              int parent = (k - 1) >>> 1;
# Line 614  Line 676 
676              siftDownComparable(k, x);              siftDownComparable(k, x);
677      }      }
678    
679        @SuppressWarnings("unchecked")
680      private void siftDownComparable(int k, E x) {      private void siftDownComparable(int k, E x) {
681          Comparable<? super E> key = (Comparable<? super E>)x;          Comparable<? super E> key = (Comparable<? super E>)x;
682          int half = size >>> 1;        // loop while a non-leaf          int half = size >>> 1;        // loop while a non-leaf
# Line 632  Line 695 
695          queue[k] = key;          queue[k] = key;
696      }      }
697    
698        @SuppressWarnings("unchecked")
699      private void siftDownUsingComparator(int k, E x) {      private void siftDownUsingComparator(int k, E x) {
700          int half = size >>> 1;          int half = size >>> 1;
701          while (k < half) {          while (k < half) {
# Line 653  Line 717 
717       * Establishes the heap invariant (described above) in the entire tree,       * Establishes the heap invariant (described above) in the entire tree,
718       * assuming nothing about the order of the elements prior to the call.       * assuming nothing about the order of the elements prior to the call.
719       */       */
720        @SuppressWarnings("unchecked")
721      private void heapify() {      private void heapify() {
722          for (int i = (size >>> 1) - 1; i >= 0; i--)          for (int i = (size >>> 1) - 1; i >= 0; i--)
723              siftDown(i, (E) queue[i]);              siftDown(i, (E) queue[i]);
# Line 672  Line 737 
737      }      }
738    
739      /**      /**
740       * Saves the state of the instance to a stream (that       * Saves this queue to a stream (that is, serializes it).
      * is, serializes it).  
741       *       *
742       * @serialData The length of the array backing the instance is       * @serialData The length of the array backing the instance is
743       *             emitted (int), followed by all of its elements       *             emitted (int), followed by all of its elements
# Line 717  Line 781 
781          // spec has never explained what that might be.          // spec has never explained what that might be.
782          heapify();          heapify();
783      }      }
784    
785        public Spliterator<E> spliterator() {
786            return new PriorityQueueSpliterator<E>(this, 0, -1, 0);
787        }
788    
789        /**
790         * This is very similar to ArrayList Spliterator, except for extra
791         * null checks.
792         */
793        static final class PriorityQueueSpliterator<E> implements Spliterator<E> {
794            private final PriorityQueue<E> pq;
795            private int index;            // current index, modified on advance/split
796            private int fence;            // -1 until first use
797            private int expectedModCount; // initialized when fence set
798    
799            /** Creates new spliterator covering the given range */
800            PriorityQueueSpliterator(PriorityQueue<E> pq, int origin, int fence,
801                                 int expectedModCount) {
802                this.pq = pq;
803                this.index = origin;
804                this.fence = fence;
805                this.expectedModCount = expectedModCount;
806            }
807    
808            private int getFence() { // initialize fence to size on first use
809                int hi;
810                if ((hi = fence) < 0) {
811                    expectedModCount = pq.modCount;
812                    hi = fence = pq.size;
813                }
814                return hi;
815            }
816    
817            public Spliterator<E> trySplit() {
818                int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
819                return (lo >= mid) ? null :
820                    new PriorityQueueSpliterator<E>(pq, lo, index = mid,
821                                                    expectedModCount);
822            }
823    
824            @SuppressWarnings("unchecked")
825            public void forEachRemaining(Consumer<? super E> action) {
826                int i, hi, mc; // hoist accesses and checks from loop
827                PriorityQueue<E> q; Object[] a;
828                if (action == null)
829                    throw new NullPointerException();
830                if ((q = pq) != null && (a = q.queue) != null) {
831                    if ((hi = fence) < 0) {
832                        mc = q.modCount;
833                        hi = q.size;
834                    }
835                    else
836                        mc = expectedModCount;
837                    if ((i = index) >= 0 && (index = hi) <= a.length) {
838                        for (E e;; ++i) {
839                            if (i < hi) {
840                                if ((e = (E) a[i]) == null) // must be CME
841                                    break;
842                                action.accept(e);
843                            }
844                            else if (q.modCount != mc)
845                                break;
846                            else
847                                return;
848                        }
849                    }
850                }
851                throw new ConcurrentModificationException();
852            }
853    
854            public boolean tryAdvance(Consumer<? super E> action) {
855                int hi = getFence(), lo = index;
856                if (lo >= 0 && lo < hi) {
857                    index = lo + 1;
858                    @SuppressWarnings("unchecked") E e = (E)pq.queue[lo];
859                    if (e == null)
860                        throw new ConcurrentModificationException();
861                    action.accept(e);
862                    if (pq.modCount != expectedModCount)
863                        throw new ConcurrentModificationException();
864                    return true;
865                }
866                return false;
867            }
868    
869            public long estimateSize() {
870                return (long) (getFence() - index);
871            }
872    
873            public int characteristics() {
874                return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;
875            }
876        }
877  }  }

Legend:
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  Added in v.1.96

Doug Lea
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