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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.114 by jsr166, Wed Nov 30 18:12:52 2016 UTC vs.
Revision 1.126 by jsr166, Sun May 6 23:07:56 2018 UTC

# Line 1 | Line 1
1   /*
2 < * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
2 > * Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
3   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4   *
5   * This code is free software; you can redistribute it and/or modify it
# Line 26 | Line 26
26   package java.util;
27  
28   import java.util.function.Consumer;
29 + import jdk.internal.misc.SharedSecrets;
30  
31   /**
32   * An unbounded priority {@linkplain Queue queue} based on a priority heap.
# Line 73 | Line 74 | import java.util.function.Consumer;
74   * ({@code peek}, {@code element}, and {@code size}).
75   *
76   * <p>This class is a member of the
77 < * <a href="{@docRoot}/../technotes/guides/collections/index.html">
77 > * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
78   * Java Collections Framework</a>.
79   *
80   * @since 1.5
81   * @author Josh Bloch, Doug Lea
82   * @param <E> the type of elements held in this queue
83   */
84 + @SuppressWarnings("unchecked")
85   public class PriorityQueue<E> extends AbstractQueue<E>
86      implements java.io.Serializable {
87  
# Line 186 | Line 188 | public class PriorityQueue<E> extends Ab
188       * @throws NullPointerException if the specified collection or any
189       *         of its elements are null
190       */
189    @SuppressWarnings("unchecked")
191      public PriorityQueue(Collection<? extends E> c) {
192          if (c instanceof SortedSet<?>) {
193              SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
# Line 218 | Line 219 | public class PriorityQueue<E> extends Ab
219       * @throws NullPointerException if the specified priority queue or any
220       *         of its elements are null
221       */
221    @SuppressWarnings("unchecked")
222      public PriorityQueue(PriorityQueue<? extends E> c) {
223          this.comparator = (Comparator<? super E>) c.comparator();
224          initFromPriorityQueue(c);
# Line 237 | Line 237 | public class PriorityQueue<E> extends Ab
237       * @throws NullPointerException if the specified sorted set or any
238       *         of its elements are null
239       */
240    @SuppressWarnings("unchecked")
240      public PriorityQueue(SortedSet<? extends E> c) {
241          this.comparator = (Comparator<? super E>) c.comparator();
242          initElementsFromCollection(c);
243      }
244  
245 +    /** Ensures that queue[0] exists, helping peek() and poll(). */
246 +    private static Object[] ensureNonEmpty(Object[] es) {
247 +        return (es.length > 0) ? es : new Object[1];
248 +    }
249 +
250      private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
251          if (c.getClass() == PriorityQueue.class) {
252 <            this.queue = c.toArray();
252 >            this.queue = ensureNonEmpty(c.toArray());
253              this.size = c.size();
254          } else {
255              initFromCollection(c);
# Line 253 | Line 257 | public class PriorityQueue<E> extends Ab
257      }
258  
259      private void initElementsFromCollection(Collection<? extends E> c) {
260 <        Object[] a = c.toArray();
260 >        Object[] es = c.toArray();
261 >        int len = es.length;
262          // If c.toArray incorrectly doesn't return Object[], copy it.
263 <        if (a.getClass() != Object[].class)
264 <            a = Arrays.copyOf(a, a.length, Object[].class);
260 <        int len = a.length;
263 >        if (es.getClass() != Object[].class)
264 >            es = Arrays.copyOf(es, len, Object[].class);
265          if (len == 1 || this.comparator != null)
266 <            for (Object e : a)
266 >            for (Object e : es)
267                  if (e == null)
268                      throw new NullPointerException();
269 <        this.queue = a;
270 <        this.size = a.length;
269 >        this.queue = ensureNonEmpty(es);
270 >        this.size = len;
271      }
272  
273      /**
# Line 343 | Line 347 | public class PriorityQueue<E> extends Ab
347          return true;
348      }
349  
346    @SuppressWarnings("unchecked")
350      public E peek() {
351 <        return (size == 0) ? null : (E) queue[0];
351 >        return (E) queue[0];
352      }
353  
354      private int indexOf(Object o) {
355          if (o != null) {
356 <            for (int i = 0; i < size; i++)
357 <                if (o.equals(queue[i]))
356 >            final Object[] es = queue;
357 >            for (int i = 0, n = size; i < n; i++)
358 >                if (o.equals(es[i]))
359                      return i;
360          }
361          return -1;
# Line 379 | Line 383 | public class PriorityQueue<E> extends Ab
383      }
384  
385      /**
386 <     * Version of remove using reference equality, not equals.
383 <     * Needed by iterator.remove.
386 >     * Identity-based version for use in Itr.remove.
387       *
388       * @param o element to be removed from this queue, if present
386     * @return {@code true} if removed
389       */
390 <    boolean removeEq(Object o) {
391 <        for (int i = 0; i < size; i++) {
392 <            if (o == queue[i]) {
390 >    void removeEq(Object o) {
391 >        final Object[] es = queue;
392 >        for (int i = 0, n = size; i < n; i++) {
393 >            if (o == es[i]) {
394                  removeAt(i);
395 <                return true;
395 >                break;
396              }
397          }
395        return false;
398      }
399  
400      /**
# Line 460 | Line 462 | public class PriorityQueue<E> extends Ab
462       *         this queue
463       * @throws NullPointerException if the specified array is null
464       */
463    @SuppressWarnings("unchecked")
465      public <T> T[] toArray(T[] a) {
466          final int size = this.size;
467          if (a.length < size)
# Line 522 | Line 523 | public class PriorityQueue<E> extends Ab
523           */
524          private int expectedModCount = modCount;
525  
526 +        Itr() {}                        // prevent access constructor creation
527 +
528          public boolean hasNext() {
529              return cursor < size ||
530                  (forgetMeNot != null && !forgetMeNot.isEmpty());
531          }
532  
530        @SuppressWarnings("unchecked")
533          public E next() {
534              if (expectedModCount != modCount)
535                  throw new ConcurrentModificationException();
# Line 575 | Line 577 | public class PriorityQueue<E> extends Ab
577       */
578      public void clear() {
579          modCount++;
580 <        for (int i = 0; i < size; i++)
581 <            queue[i] = null;
580 >        final Object[] es = queue;
581 >        for (int i = 0, n = size; i < n; i++)
582 >            es[i] = null;
583          size = 0;
584      }
585  
583    @SuppressWarnings("unchecked")
586      public E poll() {
587 <        if (size == 0)
588 <            return null;
589 <        int s = --size;
590 <        modCount++;
591 <        E result = (E) queue[0];
592 <        E x = (E) queue[s];
593 <        queue[s] = null;
594 <        if (s != 0)
595 <            siftDown(0, x);
587 >        final Object[] es;
588 >        final E result;
589 >
590 >        if ((result = (E) ((es = queue)[0])) != null) {
591 >            modCount++;
592 >            final int n;
593 >            final E x = (E) es[(n = --size)];
594 >            es[n] = null;
595 >            if (n > 0) {
596 >                final Comparator<? super E> cmp;
597 >                if ((cmp = comparator) == null)
598 >                    siftDownComparable(0, x, es, n);
599 >                else
600 >                    siftDownUsingComparator(0, x, es, n, cmp);
601 >            }
602 >        }
603          return result;
604      }
605  
# Line 606 | Line 615 | public class PriorityQueue<E> extends Ab
615       * position before i. This fact is used by iterator.remove so as to
616       * avoid missing traversing elements.
617       */
609    @SuppressWarnings("unchecked")
618      E removeAt(int i) {
619          // assert i >= 0 && i < size;
620 +        final Object[] es = queue;
621          modCount++;
622          int s = --size;
623          if (s == i) // removed last element
624 <            queue[i] = null;
624 >            es[i] = null;
625          else {
626              E moved = (E) queue[s];
627 <            queue[s] = null;
627 >            es[s] = null;
628              siftDown(i, moved);
629 <            if (queue[i] == moved) {
629 >            if (es[i] == moved) {
630                  siftUp(i, moved);
631 <                if (queue[i] != moved)
631 >                if (es[i] != moved)
632                      return moved;
633              }
634          }
# Line 631 | Line 640 | public class PriorityQueue<E> extends Ab
640       * promoting x up the tree until it is greater than or equal to
641       * its parent, or is the root.
642       *
643 <     * To simplify and speed up coercions and comparisons. the
643 >     * To simplify and speed up coercions and comparisons, the
644       * Comparable and Comparator versions are separated into different
645       * methods that are otherwise identical. (Similarly for siftDown.)
646       *
# Line 640 | Line 649 | public class PriorityQueue<E> extends Ab
649       */
650      private void siftUp(int k, E x) {
651          if (comparator != null)
652 <            siftUpUsingComparator(k, x);
652 >            siftUpUsingComparator(k, x, queue, comparator);
653          else
654 <            siftUpComparable(k, x);
654 >            siftUpComparable(k, x, queue);
655      }
656  
657 <    @SuppressWarnings("unchecked")
658 <    private void siftUpComparable(int k, E x) {
650 <        Comparable<? super E> key = (Comparable<? super E>) x;
657 >    private static <T> void siftUpComparable(int k, T x, Object[] es) {
658 >        Comparable<? super T> key = (Comparable<? super T>) x;
659          while (k > 0) {
660              int parent = (k - 1) >>> 1;
661 <            Object e = queue[parent];
662 <            if (key.compareTo((E) e) >= 0)
661 >            Object e = es[parent];
662 >            if (key.compareTo((T) e) >= 0)
663                  break;
664 <            queue[k] = e;
664 >            es[k] = e;
665              k = parent;
666          }
667 <        queue[k] = key;
667 >        es[k] = key;
668      }
669  
670 <    @SuppressWarnings("unchecked")
671 <    private void siftUpUsingComparator(int k, E x) {
670 >    private static <T> void siftUpUsingComparator(
671 >        int k, T x, Object[] es, Comparator<? super T> cmp) {
672          while (k > 0) {
673              int parent = (k - 1) >>> 1;
674 <            Object e = queue[parent];
675 <            if (comparator.compare(x, (E) e) >= 0)
674 >            Object e = es[parent];
675 >            if (cmp.compare(x, (T) e) >= 0)
676                  break;
677 <            queue[k] = e;
677 >            es[k] = e;
678              k = parent;
679          }
680 <        queue[k] = x;
680 >        es[k] = x;
681      }
682  
683      /**
# Line 682 | Line 690 | public class PriorityQueue<E> extends Ab
690       */
691      private void siftDown(int k, E x) {
692          if (comparator != null)
693 <            siftDownUsingComparator(k, x);
693 >            siftDownUsingComparator(k, x, queue, size, comparator);
694          else
695 <            siftDownComparable(k, x);
695 >            siftDownComparable(k, x, queue, size);
696      }
697  
698 <    @SuppressWarnings("unchecked")
699 <    private void siftDownComparable(int k, E x) {
700 <        Comparable<? super E> key = (Comparable<? super E>)x;
701 <        int half = size >>> 1;        // loop while a non-leaf
698 >    private static <T> void siftDownComparable(int k, T x, Object[] es, int n) {
699 >        // assert n > 0;
700 >        Comparable<? super T> key = (Comparable<? super T>)x;
701 >        int half = n >>> 1;           // loop while a non-leaf
702          while (k < half) {
703              int child = (k << 1) + 1; // assume left child is least
704 <            Object c = queue[child];
704 >            Object c = es[child];
705              int right = child + 1;
706 <            if (right < size &&
707 <                ((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
708 <                c = queue[child = right];
709 <            if (key.compareTo((E) c) <= 0)
706 >            if (right < n &&
707 >                ((Comparable<? super T>) c).compareTo((T) es[right]) > 0)
708 >                c = es[child = right];
709 >            if (key.compareTo((T) c) <= 0)
710                  break;
711 <            queue[k] = c;
711 >            es[k] = c;
712              k = child;
713          }
714 <        queue[k] = key;
714 >        es[k] = key;
715      }
716  
717 <    @SuppressWarnings("unchecked")
718 <    private void siftDownUsingComparator(int k, E x) {
719 <        int half = size >>> 1;
717 >    private static <T> void siftDownUsingComparator(
718 >        int k, T x, Object[] es, int n, Comparator<? super T> cmp) {
719 >        // assert n > 0;
720 >        int half = n >>> 1;
721          while (k < half) {
722              int child = (k << 1) + 1;
723 <            Object c = queue[child];
723 >            Object c = es[child];
724              int right = child + 1;
725 <            if (right < size &&
726 <                comparator.compare((E) c, (E) queue[right]) > 0)
727 <                c = queue[child = right];
719 <            if (comparator.compare(x, (E) c) <= 0)
725 >            if (right < n && cmp.compare((T) c, (T) es[right]) > 0)
726 >                c = es[child = right];
727 >            if (cmp.compare(x, (T) c) <= 0)
728                  break;
729 <            queue[k] = c;
729 >            es[k] = c;
730              k = child;
731          }
732 <        queue[k] = x;
732 >        es[k] = x;
733      }
734  
735      /**
# Line 729 | Line 737 | public class PriorityQueue<E> extends Ab
737       * assuming nothing about the order of the elements prior to the call.
738       * This classic algorithm due to Floyd (1964) is known to be O(size).
739       */
732    @SuppressWarnings("unchecked")
740      private void heapify() {
741          final Object[] es = queue;
742 <        final int half = (size >>> 1) - 1;
743 <        if (comparator == null)
744 <            for (int i = half; i >= 0; i--)
745 <                siftDownComparable(i, (E) es[i]);
742 >        int n = size, i = (n >>> 1) - 1;
743 >        final Comparator<? super E> cmp;
744 >        if ((cmp = comparator) == null)
745 >            for (; i >= 0; i--)
746 >                siftDownComparable(i, (E) es[i], es, n);
747          else
748 <            for (int i = half; i >= 0; i--)
749 <                siftDownUsingComparator(i, (E) es[i]);
748 >            for (; i >= 0; i--)
749 >                siftDownUsingComparator(i, (E) es[i], es, n, cmp);
750      }
751  
752      /**
# Line 772 | Line 780 | public class PriorityQueue<E> extends Ab
780          s.writeInt(Math.max(2, size + 1));
781  
782          // Write out all elements in the "proper order".
783 <        for (int i = 0; i < size; i++)
784 <            s.writeObject(queue[i]);
783 >        final Object[] es = queue;
784 >        for (int i = 0, n = size; i < n; i++)
785 >            s.writeObject(es[i]);
786      }
787  
788      /**
# Line 793 | Line 802 | public class PriorityQueue<E> extends Ab
802          // Read in (and discard) array length
803          s.readInt();
804  
805 <        queue = new Object[size];
805 >        SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, size);
806 >        final Object[] es = queue = new Object[Math.max(size, 1)];
807  
808          // Read in all elements.
809 <        for (int i = 0; i < size; i++)
810 <            queue[i] = s.readObject();
809 >        for (int i = 0, n = size; i < n; i++)
810 >            es[i] = s.readObject();
811  
812          // Elements are guaranteed to be in "proper order", but the
813          // spec has never explained what that might be.
# Line 823 | Line 833 | public class PriorityQueue<E> extends Ab
833      }
834  
835      final class PriorityQueueSpliterator implements Spliterator<E> {
826        /*
827         * This is very similar to ArrayList Spliterator, except for
828         * extra null checks.
829         */
836          private int index;            // current index, modified on advance/split
837          private int fence;            // -1 until first use
838          private int expectedModCount; // initialized when fence set
# Line 853 | Line 859 | public class PriorityQueue<E> extends Ab
859                  new PriorityQueueSpliterator(lo, index = mid, expectedModCount);
860          }
861  
856        @SuppressWarnings("unchecked")
862          public void forEachRemaining(Consumer<? super E> action) {
858            int i, hi, mc; // hoist accesses and checks from loop
859            final Object[] a;
863              if (action == null)
864                  throw new NullPointerException();
865 <            if ((a = queue) != null) {
866 <                if ((hi = fence) < 0) {
867 <                    mc = modCount;
868 <                    hi = size;
869 <                }
870 <                else
871 <                    mc = expectedModCount;
869 <                if ((i = index) >= 0 && (index = hi) <= a.length) {
870 <                    for (E e;; ++i) {
871 <                        if (i < hi) {
872 <                            if ((e = (E) a[i]) == null) // must be CME
873 <                                break;
874 <                            action.accept(e);
875 <                        }
876 <                        else if (modCount != mc)
877 <                            break;
878 <                        else
879 <                            return;
880 <                    }
881 <                }
865 >            if (fence < 0) { fence = size; expectedModCount = modCount; }
866 >            final Object[] es = queue;
867 >            int i, hi; E e;
868 >            for (i = index, index = hi = fence; i < hi; i++) {
869 >                if ((e = (E) es[i]) == null)
870 >                    break;      // must be CME
871 >                action.accept(e);
872              }
873 <            throw new ConcurrentModificationException();
873 >            if (modCount != expectedModCount)
874 >                throw new ConcurrentModificationException();
875          }
876  
877          public boolean tryAdvance(Consumer<? super E> action) {
878              if (action == null)
879                  throw new NullPointerException();
880 <            int hi = getFence(), lo = index;
881 <            if (lo >= 0 && lo < hi) {
882 <                index = lo + 1;
883 <                @SuppressWarnings("unchecked") E e = (E)queue[lo];
884 <                if (e == null)
880 >            if (fence < 0) { fence = size; expectedModCount = modCount; }
881 >            int i;
882 >            if ((i = index) < fence) {
883 >                index = i + 1;
884 >                E e;
885 >                if ((e = (E) queue[i]) == null
886 >                    || modCount != expectedModCount)
887                      throw new ConcurrentModificationException();
888                  action.accept(e);
896                if (modCount != expectedModCount)
897                    throw new ConcurrentModificationException();
889                  return true;
890              }
891              return false;
# Line 908 | Line 899 | public class PriorityQueue<E> extends Ab
899              return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;
900          }
901      }
902 +
903 +    /**
904 +     * @throws NullPointerException {@inheritDoc}
905 +     */
906 +    public void forEach(Consumer<? super E> action) {
907 +        Objects.requireNonNull(action);
908 +        final int expectedModCount = modCount;
909 +        final Object[] es = queue;
910 +        for (int i = 0, n = size; i < n; i++)
911 +            action.accept((E) es[i]);
912 +        if (expectedModCount != modCount)
913 +            throw new ConcurrentModificationException();
914 +    }
915   }

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