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/* |
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* Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved. |
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* Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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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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* <p>This class and its iterator implement all of the |
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* <em>optional</em> methods of the {@link Collection} and {@link |
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* Iterator} interfaces. The Iterator provided in method {@link |
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* #iterator()} is <em>not</em> guaranteed to traverse the elements of |
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* #iterator()} and the Spliterator provided in method {@link #spliterator()} |
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* are <em>not</em> guaranteed to traverse the elements of |
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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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* 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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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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* The number of times this priority queue has been |
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* <i>structurally modified</i>. See AbstractList for gory details. |
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*/ |
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transient int modCount = 0; // non-private to simplify nested class access |
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transient int modCount; // non-private to simplify nested class access |
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|
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/** |
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* Creates a {@code PriorityQueue} with the default initial |
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} |
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|
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/** |
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* Creates a {@code PriorityQueue} with the default initial capacity and |
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* whose elements are ordered according to the specified comparator. |
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* |
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* @param comparator the comparator that will be used to order this |
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* priority queue. If {@code null}, the {@linkplain Comparable |
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* natural ordering} of the elements will be used. |
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* @since 1.8 |
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*/ |
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public PriorityQueue(Comparator<? super E> comparator) { |
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this(DEFAULT_INITIAL_CAPACITY, comparator); |
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} |
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|
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/** |
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* Creates a {@code PriorityQueue} with the specified initial capacity |
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* that orders its elements according to the specified comparator. |
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* |
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a = Arrays.copyOf(a, a.length, Object[].class); |
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int len = a.length; |
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if (len == 1 || this.comparator != null) |
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for (int i = 0; i < len; i++) |
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if (a[i] == null) |
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for (Object e : a) |
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if (e == null) |
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throw new NullPointerException(); |
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this.queue = a; |
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this.size = a.length; |
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int i = size; |
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if (i >= queue.length) |
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grow(i + 1); |
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siftUp(i, e); |
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size = i + 1; |
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if (i == 0) |
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queue[0] = e; |
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else |
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siftUp(i, e); |
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return true; |
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} |
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|
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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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* The following code can be used to dump the queue into a newly |
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* allocated array of {@code String}: |
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* |
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* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
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* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
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* |
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* Note that {@code toArray(new Object[0])} is identical in function to |
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* {@code toArray()}. |
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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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* avoid missing traversing elements. |
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*/ |
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@SuppressWarnings("unchecked") |
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private E removeAt(int i) { |
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E removeAt(int i) { |
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// assert i >= 0 && i < size; |
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modCount++; |
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int s = --size; |
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/** |
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* Establishes the heap invariant (described above) in the entire tree, |
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* assuming nothing about the order of the elements prior to the call. |
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* This classic algorithm due to Floyd (1964) is known to be O(size). |
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*/ |
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@SuppressWarnings("unchecked") |
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private void heapify() { |
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/** |
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* Saves this queue to a stream (that is, serializes it). |
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* |
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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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* @serialData The length of the array backing the instance is |
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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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*/ |
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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 |
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* @throws ClassNotFoundException if the class of a serialized object |
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* could not be found |
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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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} |
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|
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// wrapping constructor in method avoids transient javac problems |
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final PriorityQueueSpliterator<E> spliterator(int origin, int fence, |
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int expectedModCount) { |
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return new PriorityQueueSpliterator<E>(this, origin, fence, |
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expectedModCount); |
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} |
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|
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public Stream<E> stream() { |
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int flags = Streams.STREAM_IS_SIZED; |
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return Streams.stream |
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(() -> spliterator(0, size, modCount), flags); |
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} |
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public Stream<E> parallelStream() { |
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int flags = Streams.STREAM_IS_SIZED; |
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return Streams.parallelStream |
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(() -> spliterator(0, size, modCount), flags); |
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} |
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|
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/** Index-based split-by-two Spliterator */ |
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static final class PriorityQueueSpliterator<E> implements Spliterator<E> { |
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private final PriorityQueue<E> pq; |
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private int index; // current index, modified on advance/split |
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private final int fence; // one past last index |
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private final int expectedModCount; // for comodification checks |
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|
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/** Create new spliterator covering the given range */ |
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PriorityQueueSpliterator(PriorityQueue<E> pq, int origin, int fence, |
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int expectedModCount) { |
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this.pq = pq; this.index = origin; this.fence = fence; |
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/** |
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* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em> |
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* and <em>fail-fast</em> {@link Spliterator} over the elements in this |
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* queue. The spliterator does not traverse elements in any particular order |
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* (the {@link Spliterator#ORDERED ORDERED} characteristic is not reported). |
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* |
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* <p>The {@code Spliterator} reports {@link Spliterator#SIZED}, |
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* {@link Spliterator#SUBSIZED}, and {@link Spliterator#NONNULL}. |
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* Overriding implementations should document the reporting of additional |
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* characteristic values. |
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* |
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* @return a {@code Spliterator} over the elements in this queue |
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* @since 1.8 |
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*/ |
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public final Spliterator<E> spliterator() { |
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return new PriorityQueueSpliterator(0, -1, 0); |
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} |
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|
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final class PriorityQueueSpliterator implements Spliterator<E> { |
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/* |
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* This is very similar to ArrayList Spliterator, except for |
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* extra null checks. |
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*/ |
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private int index; // current index, modified on advance/split |
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private int fence; // -1 until first use |
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private int expectedModCount; // initialized when fence set |
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> |
|
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/** Creates new spliterator covering the given range. */ |
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PriorityQueueSpliterator(int origin, int fence, int expectedModCount) { |
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this.index = origin; |
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this.fence = fence; |
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this.expectedModCount = expectedModCount; |
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} |
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|
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< |
public PriorityQueueSpliterator<E> trySplit() { |
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int lo = index, mid = (lo + fence) >>> 1; |
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> |
private int getFence() { // initialize fence to size on first use |
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> |
int hi; |
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> |
if ((hi = fence) < 0) { |
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> |
expectedModCount = modCount; |
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> |
hi = fence = size; |
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} |
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return hi; |
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} |
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> |
|
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> |
public PriorityQueueSpliterator trySplit() { |
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> |
int hi = getFence(), lo = index, mid = (lo + hi) >>> 1; |
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return (lo >= mid) ? null : |
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< |
new PriorityQueueSpliterator<E>(pq, lo, index = mid, |
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expectedModCount); |
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new PriorityQueueSpliterator(lo, index = mid, expectedModCount); |
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} |
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|
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< |
public void forEach(Block<? super E> block) { |
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Object[] a; int i, hi; // hoist accesses and checks from loop |
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< |
if (block == null) |
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> |
@SuppressWarnings("unchecked") |
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> |
public void forEachRemaining(Consumer<? super E> action) { |
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> |
int i, hi, mc; // hoist accesses and checks from loop |
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> |
final Object[] a; |
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> |
if (action == null) |
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throw new NullPointerException(); |
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< |
if ((a = pq.queue).length >= (hi = fence) && |
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< |
(i = index) >= 0 && i < hi) { |
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< |
index = hi; |
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< |
do { |
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< |
@SuppressWarnings("unchecked") E e = (E) a[i]; |
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< |
block.accept(e); |
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< |
} while (++i < hi); |
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< |
if (pq.modCount != expectedModCount) |
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< |
throw new ConcurrentModificationException(); |
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> |
if ((a = queue) != null) { |
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> |
if ((hi = fence) < 0) { |
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> |
mc = modCount; |
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> |
hi = size; |
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> |
} |
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> |
else |
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> |
mc = expectedModCount; |
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> |
if ((i = index) >= 0 && (index = hi) <= a.length) { |
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> |
for (E e;; ++i) { |
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> |
if (i < hi) { |
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if ((e = (E) a[i]) == null) // must be CME |
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break; |
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action.accept(e); |
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} |
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else if (modCount != mc) |
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break; |
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else |
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> |
return; |
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> |
} |
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> |
} |
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} |
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+ |
throw new ConcurrentModificationException(); |
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} |
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|
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< |
public boolean tryAdvance(Block<? super E> block) { |
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< |
if (index >= 0 && index < fence) { |
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< |
@SuppressWarnings("unchecked") E e = |
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< |
(E)pq.queue[index++]; |
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< |
block.accept(e); |
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< |
if (pq.modCount != expectedModCount) |
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> |
public boolean tryAdvance(Consumer<? super E> action) { |
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> |
if (action == null) |
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> |
throw new NullPointerException(); |
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> |
int hi = getFence(), lo = index; |
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> |
if (lo >= 0 && lo < hi) { |
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> |
index = lo + 1; |
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> |
@SuppressWarnings("unchecked") E e = (E)queue[lo]; |
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> |
if (e == null) |
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> |
throw new ConcurrentModificationException(); |
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> |
action.accept(e); |
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> |
if (modCount != expectedModCount) |
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throw new ConcurrentModificationException(); |
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return true; |
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} |
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return false; |
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} |
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|
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< |
public long estimateSize() { return (long)(fence - index); } |
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< |
public boolean hasExactSize() { return true; } |
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< |
public boolean hasExactSplits() { return true; } |
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> |
public long estimateSize() { |
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> |
return getFence() - index; |
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> |
} |
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> |
|
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> |
public int characteristics() { |
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> |
return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL; |
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> |
} |
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} |
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} |
