1 |
|
/* |
2 |
< |
* Copyright (c) 2003, 2006, Oracle and/or its affiliates. All rights reserved. |
2 |
> |
* Copyright (c) 2003, 2013, 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 |
6 |
|
* under the terms of the GNU General Public License version 2 only, as |
7 |
< |
* published by the Free Software Foundation. Sun designates this |
7 |
> |
* published by the Free Software Foundation. Oracle designates this |
8 |
|
* particular file as subject to the "Classpath" exception as provided |
9 |
< |
* by Sun in the LICENSE file that accompanied this code. |
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 |
25 |
|
|
26 |
|
package java.util; |
27 |
|
|
28 |
+ |
import java.util.function.Consumer; |
29 |
+ |
|
30 |
|
/** |
31 |
|
* An unbounded priority {@linkplain Queue queue} based on a priority heap. |
32 |
|
* The elements of the priority queue are ordered according to their |
58 |
|
* the priority queue in any particular order. If you need ordered |
59 |
|
* traversal, consider using {@code Arrays.sort(pq.toArray())}. |
60 |
|
* |
61 |
< |
* <p> <strong>Note that this implementation is not synchronized.</strong> |
61 |
> |
* <p><strong>Note that this implementation is not synchronized.</strong> |
62 |
|
* Multiple threads should not access a {@code PriorityQueue} |
63 |
|
* instance concurrently if any of the threads modifies the queue. |
64 |
|
* Instead, use the thread-safe {@link |
65 |
|
* java.util.concurrent.PriorityBlockingQueue} class. |
66 |
|
* |
67 |
|
* <p>Implementation note: this implementation provides |
68 |
< |
* O(log(n)) time for the enqueing and dequeing methods |
68 |
> |
* O(log(n)) time for the enqueuing and dequeuing methods |
69 |
|
* ({@code offer}, {@code poll}, {@code remove()} and {@code add}); |
70 |
|
* linear time for the {@code remove(Object)} and {@code contains(Object)} |
71 |
|
* methods; and constant time for the retrieval methods |
77 |
|
* |
78 |
|
* @since 1.5 |
79 |
|
* @author Josh Bloch, Doug Lea |
80 |
< |
* @param <E> the type of elements held in this collection |
80 |
> |
* @param <E> the type of elements held in this queue |
81 |
|
*/ |
82 |
|
public class PriorityQueue<E> extends AbstractQueue<E> |
83 |
|
implements java.io.Serializable { |
94 |
|
* 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. |
96 |
|
*/ |
97 |
< |
private transient Object[] queue; |
97 |
> |
transient Object[] queue; // non-private to simplify nested class access |
98 |
|
|
99 |
|
/** |
100 |
|
* The number of elements in the priority queue. |
101 |
|
*/ |
102 |
< |
private int size = 0; |
102 |
> |
private int size; |
103 |
|
|
104 |
|
/** |
105 |
|
* The comparator, or null if priority queue uses elements' |
111 |
|
* The number of times this priority queue has been |
112 |
|
* <i>structurally modified</i>. See AbstractList for gory details. |
113 |
|
*/ |
114 |
< |
private transient int modCount = 0; |
114 |
> |
transient int modCount; // non-private to simplify nested class access |
115 |
|
|
116 |
|
/** |
117 |
|
* Creates a {@code PriorityQueue} with the default initial |
136 |
|
} |
137 |
|
|
138 |
|
/** |
139 |
+ |
* Creates a {@code PriorityQueue} with the default initial capacity and |
140 |
+ |
* whose elements are ordered according to the specified comparator. |
141 |
+ |
* |
142 |
+ |
* @param comparator the comparator that will be used to order this |
143 |
+ |
* priority queue. If {@code null}, the {@linkplain Comparable |
144 |
+ |
* natural ordering} of the elements will be used. |
145 |
+ |
* @since 1.8 |
146 |
+ |
*/ |
147 |
+ |
public PriorityQueue(Comparator<? super E> comparator) { |
148 |
+ |
this(DEFAULT_INITIAL_CAPACITY, comparator); |
149 |
+ |
} |
150 |
+ |
|
151 |
+ |
/** |
152 |
|
* Creates a {@code PriorityQueue} with the specified initial capacity |
153 |
|
* that orders its elements according to the specified comparator. |
154 |
|
* |
258 |
|
a = Arrays.copyOf(a, a.length, Object[].class); |
259 |
|
int len = a.length; |
260 |
|
if (len == 1 || this.comparator != null) |
261 |
< |
for (int i = 0; i < len; i++) |
262 |
< |
if (a[i] == null) |
261 |
> |
for (Object e : a) |
262 |
> |
if (e == null) |
263 |
|
throw new NullPointerException(); |
264 |
|
this.queue = a; |
265 |
|
this.size = a.length; |
345 |
|
return true; |
346 |
|
} |
347 |
|
|
348 |
+ |
@SuppressWarnings("unchecked") |
349 |
|
public E peek() { |
350 |
|
return (size == 0) ? null : (E) queue[0]; |
351 |
|
} |
406 |
|
* @return {@code true} if this queue contains the specified element |
407 |
|
*/ |
408 |
|
public boolean contains(Object o) { |
409 |
< |
return indexOf(o) != -1; |
409 |
> |
return indexOf(o) >= 0; |
410 |
|
} |
411 |
|
|
412 |
|
/** |
444 |
|
* precise control over the runtime type of the output array, and may, |
445 |
|
* under certain circumstances, be used to save allocation costs. |
446 |
|
* |
447 |
< |
* <p>Suppose <tt>x</tt> is a queue known to contain only strings. |
447 |
> |
* <p>Suppose {@code x} is a queue known to contain only strings. |
448 |
|
* The following code can be used to dump the queue into a newly |
449 |
< |
* allocated array of <tt>String</tt>: |
449 |
> |
* allocated array of {@code String}: |
450 |
|
* |
451 |
< |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
451 |
> |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
452 |
|
* |
453 |
< |
* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
454 |
< |
* <tt>toArray()</tt>. |
453 |
> |
* Note that {@code toArray(new Object[0])} is identical in function to |
454 |
> |
* {@code toArray()}. |
455 |
|
* |
456 |
|
* @param a the array into which the elements of the queue are to |
457 |
|
* be stored, if it is big enough; otherwise, a new array of the |
462 |
|
* this queue |
463 |
|
* @throws NullPointerException if the specified array is null |
464 |
|
*/ |
465 |
+ |
@SuppressWarnings("unchecked") |
466 |
|
public <T> T[] toArray(T[] a) { |
467 |
+ |
final int size = this.size; |
468 |
|
if (a.length < size) |
469 |
|
// Make a new array of a's runtime type, but my contents: |
470 |
|
return (T[]) Arrays.copyOf(queue, size, a.getClass()); |
489 |
|
* Index (into queue array) of element to be returned by |
490 |
|
* subsequent call to next. |
491 |
|
*/ |
492 |
< |
private int cursor = 0; |
492 |
> |
private int cursor; |
493 |
|
|
494 |
|
/** |
495 |
|
* Index of element returned by most recent call to next, |
509 |
|
* We expect that most iterations, even those involving removals, |
510 |
|
* will not need to store elements in this field. |
511 |
|
*/ |
512 |
< |
private ArrayDeque<E> forgetMeNot = null; |
512 |
> |
private ArrayDeque<E> forgetMeNot; |
513 |
|
|
514 |
|
/** |
515 |
|
* Element returned by the most recent call to next iff that |
516 |
|
* element was drawn from the forgetMeNot list. |
517 |
|
*/ |
518 |
< |
private E lastRetElt = null; |
518 |
> |
private E lastRetElt; |
519 |
|
|
520 |
|
/** |
521 |
|
* The modCount value that the iterator believes that the backing |
529 |
|
(forgetMeNot != null && !forgetMeNot.isEmpty()); |
530 |
|
} |
531 |
|
|
532 |
+ |
@SuppressWarnings("unchecked") |
533 |
|
public E next() { |
534 |
|
if (expectedModCount != modCount) |
535 |
|
throw new ConcurrentModificationException(); |
554 |
|
cursor--; |
555 |
|
else { |
556 |
|
if (forgetMeNot == null) |
557 |
< |
forgetMeNot = new ArrayDeque<E>(); |
557 |
> |
forgetMeNot = new ArrayDeque<>(); |
558 |
|
forgetMeNot.add(moved); |
559 |
|
} |
560 |
|
} else if (lastRetElt != null) { |
582 |
|
size = 0; |
583 |
|
} |
584 |
|
|
585 |
+ |
@SuppressWarnings("unchecked") |
586 |
|
public E poll() { |
587 |
|
if (size == 0) |
588 |
|
return null; |
608 |
|
* position before i. This fact is used by iterator.remove so as to |
609 |
|
* avoid missing traversing elements. |
610 |
|
*/ |
611 |
+ |
@SuppressWarnings("unchecked") |
612 |
|
private E removeAt(int i) { |
613 |
< |
assert i >= 0 && i < size; |
613 |
> |
// assert i >= 0 && i < size; |
614 |
|
modCount++; |
615 |
|
int s = --size; |
616 |
|
if (s == i) // removed last element |
647 |
|
siftUpComparable(k, x); |
648 |
|
} |
649 |
|
|
650 |
+ |
@SuppressWarnings("unchecked") |
651 |
|
private void siftUpComparable(int k, E x) { |
652 |
|
Comparable<? super E> key = (Comparable<? super E>) x; |
653 |
|
while (k > 0) { |
661 |
|
queue[k] = key; |
662 |
|
} |
663 |
|
|
664 |
+ |
@SuppressWarnings("unchecked") |
665 |
|
private void siftUpUsingComparator(int k, E x) { |
666 |
|
while (k > 0) { |
667 |
|
int parent = (k - 1) >>> 1; |
689 |
|
siftDownComparable(k, x); |
690 |
|
} |
691 |
|
|
692 |
+ |
@SuppressWarnings("unchecked") |
693 |
|
private void siftDownComparable(int k, E x) { |
694 |
|
Comparable<? super E> key = (Comparable<? super E>)x; |
695 |
|
int half = size >>> 1; // loop while a non-leaf |
708 |
|
queue[k] = key; |
709 |
|
} |
710 |
|
|
711 |
+ |
@SuppressWarnings("unchecked") |
712 |
|
private void siftDownUsingComparator(int k, E x) { |
713 |
|
int half = size >>> 1; |
714 |
|
while (k < half) { |
730 |
|
* Establishes the heap invariant (described above) in the entire tree, |
731 |
|
* assuming nothing about the order of the elements prior to the call. |
732 |
|
*/ |
733 |
+ |
@SuppressWarnings("unchecked") |
734 |
|
private void heapify() { |
735 |
|
for (int i = (size >>> 1) - 1; i >= 0; i--) |
736 |
|
siftDown(i, (E) queue[i]); |
750 |
|
} |
751 |
|
|
752 |
|
/** |
753 |
< |
* Saves the state of the instance to a stream (that |
728 |
< |
* is, serializes it). |
753 |
> |
* Saves this queue to a stream (that is, serializes it). |
754 |
|
* |
755 |
|
* @serialData The length of the array backing the instance is |
756 |
|
* emitted (int), followed by all of its elements |
757 |
|
* (each an {@code Object}) in the proper order. |
758 |
|
* @param s the stream |
759 |
+ |
* @throws java.io.IOException if an I/O error occurs |
760 |
|
*/ |
761 |
|
private void writeObject(java.io.ObjectOutputStream s) |
762 |
< |
throws java.io.IOException{ |
762 |
> |
throws java.io.IOException { |
763 |
|
// Write out element count, and any hidden stuff |
764 |
|
s.defaultWriteObject(); |
765 |
|
|
776 |
|
* (that is, deserializes it). |
777 |
|
* |
778 |
|
* @param s the stream |
779 |
+ |
* @throws ClassNotFoundException if the class of a serialized object |
780 |
+ |
* could not be found |
781 |
+ |
* @throws java.io.IOException if an I/O error occurs |
782 |
|
*/ |
783 |
|
private void readObject(java.io.ObjectInputStream s) |
784 |
|
throws java.io.IOException, ClassNotFoundException { |
798 |
|
// spec has never explained what that might be. |
799 |
|
heapify(); |
800 |
|
} |
801 |
+ |
|
802 |
+ |
/** |
803 |
+ |
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em> |
804 |
+ |
* and <em>fail-fast</em> {@link Spliterator} over the elements in this |
805 |
+ |
* queue. |
806 |
+ |
* |
807 |
+ |
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED}, |
808 |
+ |
* {@link Spliterator#SUBSIZED}, and {@link Spliterator#NONNULL}. |
809 |
+ |
* Overriding implementations should document the reporting of additional |
810 |
+ |
* characteristic values. |
811 |
+ |
* |
812 |
+ |
* @return a {@code Spliterator} over the elements in this queue |
813 |
+ |
* @since 1.8 |
814 |
+ |
*/ |
815 |
+ |
public final Spliterator<E> spliterator() { |
816 |
+ |
return new PriorityQueueSpliterator<>(this, 0, -1, 0); |
817 |
+ |
} |
818 |
+ |
|
819 |
+ |
static final class PriorityQueueSpliterator<E> implements Spliterator<E> { |
820 |
+ |
/* |
821 |
+ |
* This is very similar to ArrayList Spliterator, except for |
822 |
+ |
* extra null checks. |
823 |
+ |
*/ |
824 |
+ |
private final PriorityQueue<E> pq; |
825 |
+ |
private int index; // current index, modified on advance/split |
826 |
+ |
private int fence; // -1 until first use |
827 |
+ |
private int expectedModCount; // initialized when fence set |
828 |
+ |
|
829 |
+ |
/** Creates new spliterator covering the given range */ |
830 |
+ |
PriorityQueueSpliterator(PriorityQueue<E> pq, int origin, int fence, |
831 |
+ |
int expectedModCount) { |
832 |
+ |
this.pq = pq; |
833 |
+ |
this.index = origin; |
834 |
+ |
this.fence = fence; |
835 |
+ |
this.expectedModCount = expectedModCount; |
836 |
+ |
} |
837 |
+ |
|
838 |
+ |
private int getFence() { // initialize fence to size on first use |
839 |
+ |
int hi; |
840 |
+ |
if ((hi = fence) < 0) { |
841 |
+ |
expectedModCount = pq.modCount; |
842 |
+ |
hi = fence = pq.size; |
843 |
+ |
} |
844 |
+ |
return hi; |
845 |
+ |
} |
846 |
+ |
|
847 |
+ |
public PriorityQueueSpliterator<E> trySplit() { |
848 |
+ |
int hi = getFence(), lo = index, mid = (lo + hi) >>> 1; |
849 |
+ |
return (lo >= mid) ? null : |
850 |
+ |
new PriorityQueueSpliterator<>(pq, lo, index = mid, |
851 |
+ |
expectedModCount); |
852 |
+ |
} |
853 |
+ |
|
854 |
+ |
@SuppressWarnings("unchecked") |
855 |
+ |
public void forEachRemaining(Consumer<? super E> action) { |
856 |
+ |
int i, hi, mc; // hoist accesses and checks from loop |
857 |
+ |
PriorityQueue<E> q; Object[] a; |
858 |
+ |
if (action == null) |
859 |
+ |
throw new NullPointerException(); |
860 |
+ |
if ((q = pq) != null && (a = q.queue) != null) { |
861 |
+ |
if ((hi = fence) < 0) { |
862 |
+ |
mc = q.modCount; |
863 |
+ |
hi = q.size; |
864 |
+ |
} |
865 |
+ |
else |
866 |
+ |
mc = expectedModCount; |
867 |
+ |
if ((i = index) >= 0 && (index = hi) <= a.length) { |
868 |
+ |
for (E e;; ++i) { |
869 |
+ |
if (i < hi) { |
870 |
+ |
if ((e = (E) a[i]) == null) // must be CME |
871 |
+ |
break; |
872 |
+ |
action.accept(e); |
873 |
+ |
} |
874 |
+ |
else if (q.modCount != mc) |
875 |
+ |
break; |
876 |
+ |
else |
877 |
+ |
return; |
878 |
+ |
} |
879 |
+ |
} |
880 |
+ |
} |
881 |
+ |
throw new ConcurrentModificationException(); |
882 |
+ |
} |
883 |
+ |
|
884 |
+ |
public boolean tryAdvance(Consumer<? super E> action) { |
885 |
+ |
if (action == null) |
886 |
+ |
throw new NullPointerException(); |
887 |
+ |
int hi = getFence(), lo = index; |
888 |
+ |
if (lo >= 0 && lo < hi) { |
889 |
+ |
index = lo + 1; |
890 |
+ |
@SuppressWarnings("unchecked") E e = (E)pq.queue[lo]; |
891 |
+ |
if (e == null) |
892 |
+ |
throw new ConcurrentModificationException(); |
893 |
+ |
action.accept(e); |
894 |
+ |
if (pq.modCount != expectedModCount) |
895 |
+ |
throw new ConcurrentModificationException(); |
896 |
+ |
return true; |
897 |
+ |
} |
898 |
+ |
return false; |
899 |
+ |
} |
900 |
+ |
|
901 |
+ |
public long estimateSize() { |
902 |
+ |
return (long) (getFence() - index); |
903 |
+ |
} |
904 |
+ |
|
905 |
+ |
public int characteristics() { |
906 |
+ |
return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL; |
907 |
+ |
} |
908 |
+ |
} |
909 |
|
} |