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*/ |
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package java.util; |
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import java.util.stream.Stream; |
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import java.util.Spliterator; |
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import java.util.stream.Streams; |
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import java.util.function.Block; |
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|
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import java.util.function.Consumer; |
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|
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/** |
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* An unbounded priority {@linkplain Queue queue} based on a priority heap. |
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* the priority queue in any particular order. If you need ordered |
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* traversal, consider using {@code Arrays.sort(pq.toArray())}. |
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* |
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* <p> <strong>Note that this implementation is not synchronized.</strong> |
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* <p><strong>Note that this implementation is not synchronized.</strong> |
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* Multiple threads should not access a {@code PriorityQueue} |
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* instance concurrently if any of the threads modifies the queue. |
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* Instead, use the thread-safe {@link |
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* java.util.concurrent.PriorityBlockingQueue} class. |
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* |
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* <p>Implementation note: this implementation provides |
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* O(log(n)) time for the enqueing and dequeing methods |
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* O(log(n)) time for the enqueuing and dequeuing methods |
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* ({@code offer}, {@code poll}, {@code remove()} and {@code add}); |
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* linear time for the {@code remove(Object)} and {@code contains(Object)} |
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* methods; and constant time for the retrieval methods |
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* |
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* @since 1.5 |
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* @author Josh Bloch, Doug Lea |
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* @param <E> the type of elements held in this collection |
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* @param <E> the type of elements held in this queue |
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*/ |
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public class PriorityQueue<E> extends AbstractQueue<E> |
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implements java.io.Serializable { |
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/** |
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* The number of elements in the priority queue. |
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*/ |
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private int size = 0; |
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private int size; |
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|
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/** |
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* The comparator, or null if priority queue uses elements' |
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* @return {@code true} if this queue contains the specified element |
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*/ |
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public boolean contains(Object o) { |
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return indexOf(o) != -1; |
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return indexOf(o) >= 0; |
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} |
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|
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/** |
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* this queue |
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* @throws NullPointerException if the specified array is null |
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*/ |
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@SuppressWarnings("unchecked") |
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public <T> T[] toArray(T[] a) { |
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final int size = this.size; |
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if (a.length < size) |
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// Make a new array of a's runtime type, but my contents: |
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return (T[]) Arrays.copyOf(queue, size, a.getClass()); |
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* Index (into queue array) of element to be returned by |
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* subsequent call to next. |
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*/ |
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private int cursor = 0; |
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private int cursor; |
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|
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/** |
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* Index of element returned by most recent call to next, |
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* We expect that most iterations, even those involving removals, |
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* will not need to store elements in this field. |
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*/ |
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private ArrayDeque<E> forgetMeNot = null; |
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private ArrayDeque<E> forgetMeNot; |
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|
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/** |
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* Element returned by the most recent call to next iff that |
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* element was drawn from the forgetMeNot list. |
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*/ |
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private E lastRetElt = null; |
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private E lastRetElt; |
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|
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/** |
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* The modCount value that the iterator believes that the backing |
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cursor--; |
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else { |
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if (forgetMeNot == null) |
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forgetMeNot = new ArrayDeque<E>(); |
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forgetMeNot = new ArrayDeque<>(); |
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forgetMeNot.add(moved); |
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} |
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} else if (lastRetElt != null) { |
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* emitted (int), followed by all of its elements |
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* (each an {@code Object}) in the proper order. |
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* @param s the stream |
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* @throws java.io.IOException if an I/O error occurs |
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*/ |
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private void writeObject(java.io.ObjectOutputStream s) |
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throws java.io.IOException { |
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* (that is, deserializes it). |
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* |
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* @param s the stream |
766 |
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* @throws ClassNotFoundException if the class of a serialized object |
767 |
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* could not be found |
768 |
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* @throws java.io.IOException if an I/O error occurs |
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*/ |
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private void readObject(java.io.ObjectInputStream s) |
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throws java.io.IOException, ClassNotFoundException { |
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heapify(); |
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} |
788 |
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|
789 |
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// wrapping constructor in method avoids transient javac problems |
790 |
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final PriorityQueueSpliterator<E> spliterator(int origin, int fence, |
791 |
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int expectedModCount) { |
792 |
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return new PriorityQueueSpliterator(this, origin, fence, |
793 |
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expectedModCount); |
794 |
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} |
795 |
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|
796 |
< |
public Stream<E> stream() { |
797 |
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int flags = Streams.STREAM_IS_SIZED; |
794 |
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return Streams.stream |
795 |
< |
(() -> spliterator(0, size, modCount), flags); |
796 |
< |
} |
797 |
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public Stream<E> parallelStream() { |
798 |
< |
int flags = Streams.STREAM_IS_SIZED; |
799 |
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return Streams.parallelStream |
800 |
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(() -> spliterator(0, size, modCount), flags); |
801 |
< |
} |
802 |
< |
|
803 |
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/** Index-based split-by-two Spliterator */ |
804 |
< |
static final class PriorityQueueSpliterator<E> |
805 |
< |
implements Spliterator<E>, Iterator<E> { |
789 |
> |
public Spliterator<E> spliterator() { |
790 |
> |
return new PriorityQueueSpliterator<E>(this, 0, -1, 0); |
791 |
> |
} |
792 |
> |
|
793 |
> |
/** |
794 |
> |
* This is very similar to ArrayList Spliterator, except for extra |
795 |
> |
* null checks. |
796 |
> |
*/ |
797 |
> |
static final class PriorityQueueSpliterator<E> implements Spliterator<E> { |
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private final PriorityQueue<E> pq; |
799 |
< |
private int index; // current index, modified on advance/split |
800 |
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private final int fence; // one past last index |
801 |
< |
private final int expectedModCount; // for comodification checks |
799 |
> |
private int index; // current index, modified on advance/split |
800 |
> |
private int fence; // -1 until first use |
801 |
> |
private int expectedModCount; // initialized when fence set |
802 |
|
|
803 |
< |
/** Create new spliterator covering the given range */ |
803 |
> |
/** Creates new spliterator covering the given range */ |
804 |
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PriorityQueueSpliterator(PriorityQueue<E> pq, int origin, int fence, |
805 |
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int expectedModCount) { |
806 |
< |
this.pq = pq; this.index = origin; this.fence = fence; |
806 |
> |
this.pq = pq; |
807 |
> |
this.index = origin; |
808 |
> |
this.fence = fence; |
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|
this.expectedModCount = expectedModCount; |
810 |
|
} |
811 |
|
|
812 |
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public PriorityQueueSpliterator<E> trySplit() { |
813 |
< |
int lo = index, mid = (lo + fence) >>> 1; |
812 |
> |
private int getFence() { // initialize fence to size on first use |
813 |
> |
int hi; |
814 |
> |
if ((hi = fence) < 0) { |
815 |
> |
expectedModCount = pq.modCount; |
816 |
> |
hi = fence = pq.size; |
817 |
> |
} |
818 |
> |
return hi; |
819 |
> |
} |
820 |
> |
|
821 |
> |
public Spliterator<E> trySplit() { |
822 |
> |
int hi = getFence(), lo = index, mid = (lo + hi) >>> 1; |
823 |
|
return (lo >= mid) ? null : |
824 |
|
new PriorityQueueSpliterator<E>(pq, lo, index = mid, |
825 |
< |
expectedModCount); |
825 |
> |
expectedModCount); |
826 |
|
} |
827 |
|
|
828 |
< |
public void forEach(Block<? super E> block) { |
829 |
< |
Object[] a; int i, hi; // hoist accesses and checks from loop |
830 |
< |
if (block == null) |
828 |
> |
@SuppressWarnings("unchecked") |
829 |
> |
public void forEachRemaining(Consumer<? super E> action) { |
830 |
> |
int i, hi, mc; // hoist accesses and checks from loop |
831 |
> |
PriorityQueue<E> q; Object[] a; |
832 |
> |
if (action == null) |
833 |
|
throw new NullPointerException(); |
834 |
< |
if ((a = pq.queue).length >= (hi = fence) && |
835 |
< |
(i = index) >= 0 && i < hi) { |
836 |
< |
index = hi; |
837 |
< |
do { |
838 |
< |
@SuppressWarnings("unchecked") E e = (E) a[i]; |
839 |
< |
block.accept(e); |
840 |
< |
} while (++i < hi); |
841 |
< |
if (pq.modCount != expectedModCount) |
842 |
< |
throw new ConcurrentModificationException(); |
834 |
> |
if ((q = pq) != null && (a = q.queue) != null) { |
835 |
> |
if ((hi = fence) < 0) { |
836 |
> |
mc = q.modCount; |
837 |
> |
hi = q.size; |
838 |
> |
} |
839 |
> |
else |
840 |
> |
mc = expectedModCount; |
841 |
> |
if ((i = index) >= 0 && (index = hi) <= a.length) { |
842 |
> |
for (E e;; ++i) { |
843 |
> |
if (i < hi) { |
844 |
> |
if ((e = (E) a[i]) == null) // must be CME |
845 |
> |
break; |
846 |
> |
action.accept(e); |
847 |
> |
} |
848 |
> |
else if (q.modCount != mc) |
849 |
> |
break; |
850 |
> |
else |
851 |
> |
return; |
852 |
> |
} |
853 |
> |
} |
854 |
|
} |
855 |
+ |
throw new ConcurrentModificationException(); |
856 |
|
} |
857 |
|
|
858 |
< |
public boolean tryAdvance(Block<? super E> block) { |
859 |
< |
if (index >= 0 && index < fence) { |
858 |
> |
public boolean tryAdvance(Consumer<? super E> action) { |
859 |
> |
int hi = getFence(), lo = index; |
860 |
> |
if (lo >= 0 && lo < hi) { |
861 |
> |
index = lo + 1; |
862 |
> |
@SuppressWarnings("unchecked") E e = (E)pq.queue[lo]; |
863 |
> |
if (e == null) |
864 |
> |
throw new ConcurrentModificationException(); |
865 |
> |
action.accept(e); |
866 |
|
if (pq.modCount != expectedModCount) |
867 |
|
throw new ConcurrentModificationException(); |
845 |
– |
@SuppressWarnings("unchecked") E e = |
846 |
– |
(E)pq.queue[index++]; |
847 |
– |
block.accept(e); |
868 |
|
return true; |
869 |
|
} |
870 |
|
return false; |
871 |
|
} |
872 |
|
|
873 |
< |
public long estimateSize() { return (long)(fence - index); } |
874 |
< |
public boolean hasExactSize() { return true; } |
875 |
< |
public boolean hasExactSplits() { return true; } |
856 |
< |
|
857 |
< |
// Iterator support |
858 |
< |
public Iterator<E> iterator() { return this; } |
859 |
< |
public void remove() { throw new UnsupportedOperationException(); } |
860 |
< |
public boolean hasNext() { return index >= 0 && index < fence; } |
873 |
> |
public long estimateSize() { |
874 |
> |
return (long) (getFence() - index); |
875 |
> |
} |
876 |
|
|
877 |
< |
public E next() { |
878 |
< |
if (index < 0 || index >= fence) |
864 |
< |
throw new NoSuchElementException(); |
865 |
< |
if (pq.modCount != expectedModCount) |
866 |
< |
throw new ConcurrentModificationException(); |
867 |
< |
@SuppressWarnings("unchecked") E e = |
868 |
< |
(E) pq.queue[index++]; |
869 |
< |
return e; |
877 |
> |
public int characteristics() { |
878 |
> |
return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL; |
879 |
|
} |
880 |
|
} |
881 |
|
} |