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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.115 by jsr166, Fri Dec 2 07:11:36 2016 UTC vs.
Revision 1.133 by jsr166, Thu Oct 10 16:53:08 2019 UTC

# Line 1 | Line 1
1   /*
2 < * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
2 > * Copyright (c) 2003, 2019, 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 java.util.function.Predicate;
30 + // OPENJDK import jdk.internal.access.SharedSecrets;
31 + import jdk.internal.util.ArraysSupport;
32  
33   /**
34   * An unbounded priority {@linkplain Queue queue} based on a priority heap.
# Line 73 | Line 76 | import java.util.function.Consumer;
76   * ({@code peek}, {@code element}, and {@code size}).
77   *
78   * <p>This class is a member of the
79 < * <a href="{@docRoot}/../technotes/guides/collections/index.html">
79 > * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
80   * Java Collections Framework</a>.
81   *
82   * @since 1.5
83   * @author Josh Bloch, Doug Lea
84   * @param <E> the type of elements held in this queue
85   */
86 + @SuppressWarnings("unchecked")
87   public class PriorityQueue<E> extends AbstractQueue<E>
88      implements java.io.Serializable {
89  
90 +    // OPENJDK @java.io.Serial
91      private static final long serialVersionUID = -7720805057305804111L;
92  
93      private static final int DEFAULT_INITIAL_CAPACITY = 11;
# Line 106 | Line 111 | public class PriorityQueue<E> extends Ab
111       * The comparator, or null if priority queue uses elements'
112       * natural ordering.
113       */
114 +    @SuppressWarnings("serial") // Conditionally serializable
115      private final Comparator<? super E> comparator;
116  
117      /**
# Line 186 | Line 192 | public class PriorityQueue<E> extends Ab
192       * @throws NullPointerException if the specified collection or any
193       *         of its elements are null
194       */
189    @SuppressWarnings("unchecked")
195      public PriorityQueue(Collection<? extends E> c) {
196          if (c instanceof SortedSet<?>) {
197              SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
# Line 218 | Line 223 | public class PriorityQueue<E> extends Ab
223       * @throws NullPointerException if the specified priority queue or any
224       *         of its elements are null
225       */
221    @SuppressWarnings("unchecked")
226      public PriorityQueue(PriorityQueue<? extends E> c) {
227          this.comparator = (Comparator<? super E>) c.comparator();
228          initFromPriorityQueue(c);
# Line 237 | Line 241 | public class PriorityQueue<E> extends Ab
241       * @throws NullPointerException if the specified sorted set or any
242       *         of its elements are null
243       */
240    @SuppressWarnings("unchecked")
244      public PriorityQueue(SortedSet<? extends E> c) {
245          this.comparator = (Comparator<? super E>) c.comparator();
246          initElementsFromCollection(c);
247      }
248  
249 +    /** Ensures that queue[0] exists, helping peek() and poll(). */
250 +    private static Object[] ensureNonEmpty(Object[] es) {
251 +        return (es.length > 0) ? es : new Object[1];
252 +    }
253 +
254      private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
255          if (c.getClass() == PriorityQueue.class) {
256 <            this.queue = c.toArray();
256 >            this.queue = ensureNonEmpty(c.toArray());
257              this.size = c.size();
258          } else {
259              initFromCollection(c);
# Line 253 | Line 261 | public class PriorityQueue<E> extends Ab
261      }
262  
263      private void initElementsFromCollection(Collection<? extends E> c) {
264 <        Object[] a = c.toArray();
264 >        Object[] es = c.toArray();
265 >        int len = es.length;
266          // If c.toArray incorrectly doesn't return Object[], copy it.
267 <        if (a.getClass() != Object[].class)
268 <            a = Arrays.copyOf(a, a.length, Object[].class);
260 <        int len = a.length;
267 >        if (es.getClass() != Object[].class)
268 >            es = Arrays.copyOf(es, len, Object[].class);
269          if (len == 1 || this.comparator != null)
270 <            for (Object e : a)
270 >            for (Object e : es)
271                  if (e == null)
272                      throw new NullPointerException();
273 <        this.queue = a;
274 <        this.size = a.length;
273 >        this.queue = ensureNonEmpty(es);
274 >        this.size = len;
275      }
276  
277      /**
# Line 277 | Line 285 | public class PriorityQueue<E> extends Ab
285      }
286  
287      /**
280     * The maximum size of array to allocate.
281     * Some VMs reserve some header words in an array.
282     * Attempts to allocate larger arrays may result in
283     * OutOfMemoryError: Requested array size exceeds VM limit
284     */
285    private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
286
287    /**
288       * Increases the capacity of the array.
289       *
290       * @param minCapacity the desired minimum capacity
# Line 292 | Line 292 | public class PriorityQueue<E> extends Ab
292      private void grow(int minCapacity) {
293          int oldCapacity = queue.length;
294          // Double size if small; else grow by 50%
295 <        int newCapacity = oldCapacity + ((oldCapacity < 64) ?
296 <                                         (oldCapacity + 2) :
297 <                                         (oldCapacity >> 1));
298 <        // overflow-conscious code
299 <        if (newCapacity - MAX_ARRAY_SIZE > 0)
300 <            newCapacity = hugeCapacity(minCapacity);
295 >        int newCapacity = ArraysSupport.newLength(oldCapacity,
296 >                minCapacity - oldCapacity, /* minimum growth */
297 >                oldCapacity < 64 ? oldCapacity + 2 : oldCapacity >> 1
298 >                                           /* preferred growth */);
299          queue = Arrays.copyOf(queue, newCapacity);
300      }
301  
304    private static int hugeCapacity(int minCapacity) {
305        if (minCapacity < 0) // overflow
306            throw new OutOfMemoryError();
307        return (minCapacity > MAX_ARRAY_SIZE) ?
308            Integer.MAX_VALUE :
309            MAX_ARRAY_SIZE;
310    }
311
302      /**
303       * Inserts the specified element into this priority queue.
304       *
# Line 343 | Line 333 | public class PriorityQueue<E> extends Ab
333          return true;
334      }
335  
346    @SuppressWarnings("unchecked")
336      public E peek() {
337 <        return (size == 0) ? null : (E) queue[0];
337 >        return (E) queue[0];
338      }
339  
340      private int indexOf(Object o) {
341          if (o != null) {
342 <            for (int i = 0; i < size; i++)
343 <                if (o.equals(queue[i]))
342 >            final Object[] es = queue;
343 >            for (int i = 0, n = size; i < n; i++)
344 >                if (o.equals(es[i]))
345                      return i;
346          }
347          return -1;
# Line 379 | Line 369 | public class PriorityQueue<E> extends Ab
369      }
370  
371      /**
372 <     * Version of remove using reference equality, not equals.
383 <     * Needed by iterator.remove.
372 >     * Identity-based version for use in Itr.remove.
373       *
374       * @param o element to be removed from this queue, if present
386     * @return {@code true} if removed
375       */
376 <    boolean removeEq(Object o) {
377 <        for (int i = 0; i < size; i++) {
378 <            if (o == queue[i]) {
376 >    void removeEq(Object o) {
377 >        final Object[] es = queue;
378 >        for (int i = 0, n = size; i < n; i++) {
379 >            if (o == es[i]) {
380                  removeAt(i);
381 <                return true;
381 >                break;
382              }
383          }
395        return false;
384      }
385  
386      /**
# Line 460 | Line 448 | public class PriorityQueue<E> extends Ab
448       *         this queue
449       * @throws NullPointerException if the specified array is null
450       */
463    @SuppressWarnings("unchecked")
451      public <T> T[] toArray(T[] a) {
452          final int size = this.size;
453          if (a.length < size)
# Line 522 | Line 509 | public class PriorityQueue<E> extends Ab
509           */
510          private int expectedModCount = modCount;
511  
512 +        Itr() {}                        // prevent access constructor creation
513 +
514          public boolean hasNext() {
515              return cursor < size ||
516                  (forgetMeNot != null && !forgetMeNot.isEmpty());
517          }
518  
530        @SuppressWarnings("unchecked")
519          public E next() {
520              if (expectedModCount != modCount)
521                  throw new ConcurrentModificationException();
# Line 575 | Line 563 | public class PriorityQueue<E> extends Ab
563       */
564      public void clear() {
565          modCount++;
566 <        for (int i = 0; i < size; i++)
567 <            queue[i] = null;
566 >        final Object[] es = queue;
567 >        for (int i = 0, n = size; i < n; i++)
568 >            es[i] = null;
569          size = 0;
570      }
571  
583    @SuppressWarnings("unchecked")
572      public E poll() {
573 <        if (size == 0)
574 <            return null;
575 <        int s = --size;
576 <        modCount++;
577 <        E result = (E) queue[0];
578 <        E x = (E) queue[s];
579 <        queue[s] = null;
580 <        if (s != 0)
581 <            siftDown(0, x);
573 >        final Object[] es;
574 >        final E result;
575 >
576 >        if ((result = (E) ((es = queue)[0])) != null) {
577 >            modCount++;
578 >            final int n;
579 >            final E x = (E) es[(n = --size)];
580 >            es[n] = null;
581 >            if (n > 0) {
582 >                final Comparator<? super E> cmp;
583 >                if ((cmp = comparator) == null)
584 >                    siftDownComparable(0, x, es, n);
585 >                else
586 >                    siftDownUsingComparator(0, x, es, n, cmp);
587 >            }
588 >        }
589          return result;
590      }
591  
# Line 606 | Line 601 | public class PriorityQueue<E> extends Ab
601       * position before i. This fact is used by iterator.remove so as to
602       * avoid missing traversing elements.
603       */
609    @SuppressWarnings("unchecked")
604      E removeAt(int i) {
605          // assert i >= 0 && i < size;
606 +        final Object[] es = queue;
607          modCount++;
608          int s = --size;
609          if (s == i) // removed last element
610 <            queue[i] = null;
610 >            es[i] = null;
611          else {
612 <            E moved = (E) queue[s];
613 <            queue[s] = null;
612 >            E moved = (E) es[s];
613 >            es[s] = null;
614              siftDown(i, moved);
615 <            if (queue[i] == moved) {
615 >            if (es[i] == moved) {
616                  siftUp(i, moved);
617 <                if (queue[i] != moved)
617 >                if (es[i] != moved)
618                      return moved;
619              }
620          }
# Line 631 | Line 626 | public class PriorityQueue<E> extends Ab
626       * promoting x up the tree until it is greater than or equal to
627       * its parent, or is the root.
628       *
629 <     * To simplify and speed up coercions and comparisons. the
629 >     * To simplify and speed up coercions and comparisons, the
630       * Comparable and Comparator versions are separated into different
631       * methods that are otherwise identical. (Similarly for siftDown.)
632       *
# Line 640 | Line 635 | public class PriorityQueue<E> extends Ab
635       */
636      private void siftUp(int k, E x) {
637          if (comparator != null)
638 <            siftUpUsingComparator(k, x);
638 >            siftUpUsingComparator(k, x, queue, comparator);
639          else
640 <            siftUpComparable(k, x);
640 >            siftUpComparable(k, x, queue);
641      }
642  
643 <    @SuppressWarnings("unchecked")
644 <    private void siftUpComparable(int k, E x) {
650 <        Comparable<? super E> key = (Comparable<? super E>) x;
643 >    private static <T> void siftUpComparable(int k, T x, Object[] es) {
644 >        Comparable<? super T> key = (Comparable<? super T>) x;
645          while (k > 0) {
646              int parent = (k - 1) >>> 1;
647 <            Object e = queue[parent];
648 <            if (key.compareTo((E) e) >= 0)
647 >            Object e = es[parent];
648 >            if (key.compareTo((T) e) >= 0)
649                  break;
650 <            queue[k] = e;
650 >            es[k] = e;
651              k = parent;
652          }
653 <        queue[k] = key;
653 >        es[k] = key;
654      }
655  
656 <    @SuppressWarnings("unchecked")
657 <    private void siftUpUsingComparator(int k, E x) {
656 >    private static <T> void siftUpUsingComparator(
657 >        int k, T x, Object[] es, Comparator<? super T> cmp) {
658          while (k > 0) {
659              int parent = (k - 1) >>> 1;
660 <            Object e = queue[parent];
661 <            if (comparator.compare(x, (E) e) >= 0)
660 >            Object e = es[parent];
661 >            if (cmp.compare(x, (T) e) >= 0)
662                  break;
663 <            queue[k] = e;
663 >            es[k] = e;
664              k = parent;
665          }
666 <        queue[k] = x;
666 >        es[k] = x;
667      }
668  
669      /**
# Line 682 | Line 676 | public class PriorityQueue<E> extends Ab
676       */
677      private void siftDown(int k, E x) {
678          if (comparator != null)
679 <            siftDownUsingComparator(k, x);
679 >            siftDownUsingComparator(k, x, queue, size, comparator);
680          else
681 <            siftDownComparable(k, x);
681 >            siftDownComparable(k, x, queue, size);
682      }
683  
684 <    @SuppressWarnings("unchecked")
685 <    private void siftDownComparable(int k, E x) {
686 <        Comparable<? super E> key = (Comparable<? super E>)x;
687 <        int half = size >>> 1;        // loop while a non-leaf
684 >    private static <T> void siftDownComparable(int k, T x, Object[] es, int n) {
685 >        // assert n > 0;
686 >        Comparable<? super T> key = (Comparable<? super T>)x;
687 >        int half = n >>> 1;           // loop while a non-leaf
688          while (k < half) {
689              int child = (k << 1) + 1; // assume left child is least
690 <            Object c = queue[child];
690 >            Object c = es[child];
691              int right = child + 1;
692 <            if (right < size &&
693 <                ((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
694 <                c = queue[child = right];
695 <            if (key.compareTo((E) c) <= 0)
692 >            if (right < n &&
693 >                ((Comparable<? super T>) c).compareTo((T) es[right]) > 0)
694 >                c = es[child = right];
695 >            if (key.compareTo((T) c) <= 0)
696                  break;
697 <            queue[k] = c;
697 >            es[k] = c;
698              k = child;
699          }
700 <        queue[k] = key;
700 >        es[k] = key;
701      }
702  
703 <    @SuppressWarnings("unchecked")
704 <    private void siftDownUsingComparator(int k, E x) {
705 <        int half = size >>> 1;
703 >    private static <T> void siftDownUsingComparator(
704 >        int k, T x, Object[] es, int n, Comparator<? super T> cmp) {
705 >        // assert n > 0;
706 >        int half = n >>> 1;
707          while (k < half) {
708              int child = (k << 1) + 1;
709 <            Object c = queue[child];
709 >            Object c = es[child];
710              int right = child + 1;
711 <            if (right < size &&
712 <                comparator.compare((E) c, (E) queue[right]) > 0)
713 <                c = queue[child = right];
719 <            if (comparator.compare(x, (E) c) <= 0)
711 >            if (right < n && cmp.compare((T) c, (T) es[right]) > 0)
712 >                c = es[child = right];
713 >            if (cmp.compare(x, (T) c) <= 0)
714                  break;
715 <            queue[k] = c;
715 >            es[k] = c;
716              k = child;
717          }
718 <        queue[k] = x;
718 >        es[k] = x;
719      }
720  
721      /**
# Line 729 | Line 723 | public class PriorityQueue<E> extends Ab
723       * assuming nothing about the order of the elements prior to the call.
724       * This classic algorithm due to Floyd (1964) is known to be O(size).
725       */
732    @SuppressWarnings("unchecked")
726      private void heapify() {
727          final Object[] es = queue;
728 <        final int half = (size >>> 1) - 1;
729 <        if (comparator == null)
730 <            for (int i = half; i >= 0; i--)
731 <                siftDownComparable(i, (E) es[i]);
728 >        int n = size, i = (n >>> 1) - 1;
729 >        final Comparator<? super E> cmp;
730 >        if ((cmp = comparator) == null)
731 >            for (; i >= 0; i--)
732 >                siftDownComparable(i, (E) es[i], es, n);
733          else
734 <            for (int i = half; i >= 0; i--)
735 <                siftDownUsingComparator(i, (E) es[i]);
734 >            for (; i >= 0; i--)
735 >                siftDownUsingComparator(i, (E) es[i], es, n, cmp);
736      }
737  
738      /**
# Line 763 | Line 757 | public class PriorityQueue<E> extends Ab
757       *             emitted (int), followed by all of its elements
758       *             (each an {@code Object}) in the proper order.
759       */
760 +    // OPENJDK @java.io.Serial
761      private void writeObject(java.io.ObjectOutputStream s)
762          throws java.io.IOException {
763          // Write out element count, and any hidden stuff
# Line 772 | Line 767 | public class PriorityQueue<E> extends Ab
767          s.writeInt(Math.max(2, size + 1));
768  
769          // Write out all elements in the "proper order".
770 <        for (int i = 0; i < size; i++)
771 <            s.writeObject(queue[i]);
770 >        final Object[] es = queue;
771 >        for (int i = 0, n = size; i < n; i++)
772 >            s.writeObject(es[i]);
773      }
774  
775      /**
# Line 785 | Line 781 | public class PriorityQueue<E> extends Ab
781       *         could not be found
782       * @throws java.io.IOException if an I/O error occurs
783       */
784 +    // OPENJDK @java.io.Serial
785      private void readObject(java.io.ObjectInputStream s)
786          throws java.io.IOException, ClassNotFoundException {
787          // Read in size, and any hidden stuff
# Line 793 | Line 790 | public class PriorityQueue<E> extends Ab
790          // Read in (and discard) array length
791          s.readInt();
792  
793 <        queue = new Object[size];
793 >        jsr166.Platform.checkArray(s, Object[].class, size);
794 >        final Object[] es = queue = new Object[Math.max(size, 1)];
795  
796          // Read in all elements.
797 <        for (int i = 0; i < size; i++)
798 <            queue[i] = s.readObject();
797 >        for (int i = 0, n = size; i < n; i++)
798 >            es[i] = s.readObject();
799  
800          // Elements are guaranteed to be in "proper order", but the
801          // spec has never explained what that might be.
# Line 849 | Line 847 | public class PriorityQueue<E> extends Ab
847                  new PriorityQueueSpliterator(lo, index = mid, expectedModCount);
848          }
849  
852        @SuppressWarnings("unchecked")
850          public void forEachRemaining(Consumer<? super E> action) {
851              if (action == null)
852                  throw new NullPointerException();
853              if (fence < 0) { fence = size; expectedModCount = modCount; }
854 <            final Object[] a = queue;
854 >            final Object[] es = queue;
855              int i, hi; E e;
856              for (i = index, index = hi = fence; i < hi; i++) {
857 <                if ((e = (E) a[i]) == null)
857 >                if ((e = (E) es[i]) == null)
858                      break;      // must be CME
859                  action.accept(e);
860              }
# Line 865 | Line 862 | public class PriorityQueue<E> extends Ab
862                  throw new ConcurrentModificationException();
863          }
864  
868        @SuppressWarnings("unchecked")
865          public boolean tryAdvance(Consumer<? super E> action) {
866              if (action == null)
867                  throw new NullPointerException();
# Line 891 | Line 887 | public class PriorityQueue<E> extends Ab
887              return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;
888          }
889      }
890 +
891 +    /**
892 +     * @throws NullPointerException {@inheritDoc}
893 +     */
894 +    public boolean removeIf(Predicate<? super E> filter) {
895 +        Objects.requireNonNull(filter);
896 +        return bulkRemove(filter);
897 +    }
898 +
899 +    /**
900 +     * @throws NullPointerException {@inheritDoc}
901 +     */
902 +    public boolean removeAll(Collection<?> c) {
903 +        Objects.requireNonNull(c);
904 +        return bulkRemove(e -> c.contains(e));
905 +    }
906 +
907 +    /**
908 +     * @throws NullPointerException {@inheritDoc}
909 +     */
910 +    public boolean retainAll(Collection<?> c) {
911 +        Objects.requireNonNull(c);
912 +        return bulkRemove(e -> !c.contains(e));
913 +    }
914 +
915 +    // A tiny bit set implementation
916 +
917 +    private static long[] nBits(int n) {
918 +        return new long[((n - 1) >> 6) + 1];
919 +    }
920 +    private static void setBit(long[] bits, int i) {
921 +        bits[i >> 6] |= 1L << i;
922 +    }
923 +    private static boolean isClear(long[] bits, int i) {
924 +        return (bits[i >> 6] & (1L << i)) == 0;
925 +    }
926 +
927 +    /** Implementation of bulk remove methods. */
928 +    private boolean bulkRemove(Predicate<? super E> filter) {
929 +        final int expectedModCount = ++modCount;
930 +        final Object[] es = queue;
931 +        final int end = size;
932 +        int i;
933 +        // Optimize for initial run of survivors
934 +        for (i = 0; i < end && !filter.test((E) es[i]); i++)
935 +            ;
936 +        if (i >= end) {
937 +            if (modCount != expectedModCount)
938 +                throw new ConcurrentModificationException();
939 +            return false;
940 +        }
941 +        // Tolerate predicates that reentrantly access the collection for
942 +        // read (but writers still get CME), so traverse once to find
943 +        // elements to delete, a second pass to physically expunge.
944 +        final int beg = i;
945 +        final long[] deathRow = nBits(end - beg);
946 +        deathRow[0] = 1L;   // set bit 0
947 +        for (i = beg + 1; i < end; i++)
948 +            if (filter.test((E) es[i]))
949 +                setBit(deathRow, i - beg);
950 +        if (modCount != expectedModCount)
951 +            throw new ConcurrentModificationException();
952 +        int w = beg;
953 +        for (i = beg; i < end; i++)
954 +            if (isClear(deathRow, i - beg))
955 +                es[w++] = es[i];
956 +        for (i = size = w; i < end; i++)
957 +            es[i] = null;
958 +        heapify();
959 +        return true;
960 +    }
961 +
962 +    /**
963 +     * @throws NullPointerException {@inheritDoc}
964 +     */
965 +    public void forEach(Consumer<? super E> action) {
966 +        Objects.requireNonNull(action);
967 +        final int expectedModCount = modCount;
968 +        final Object[] es = queue;
969 +        for (int i = 0, n = size; i < n; i++)
970 +            action.accept((E) es[i]);
971 +        if (expectedModCount != modCount)
972 +            throw new ConcurrentModificationException();
973 +    }
974   }

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