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/* |
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* Copyright (c) 2003, 2006, Oracle and/or its affiliates. All rights reserved. |
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* Copyright (c) 2003, 2012, 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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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. Sun designates this |
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* published by the Free Software Foundation. Oracle designates this |
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* particular file as subject to the "Classpath" exception as provided |
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* by Sun in the LICENSE file that accompanied this code. |
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* by Oracle in the LICENSE file that accompanied this code. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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*/ |
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package java.util; |
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import java.util.function.Consumer; |
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import java.util.stream.Stream; |
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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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* heap and each descendant d of n, n <= d. The element with the |
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* lowest value is in queue[0], assuming the queue is nonempty. |
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*/ |
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private transient Object[] queue; |
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transient Object[] queue; // non-private to simplify nested class access |
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|
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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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* 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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private transient int modCount = 0; |
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transient int modCount = 0; // 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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return true; |
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} |
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|
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@SuppressWarnings("unchecked") |
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public E peek() { |
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return (size == 0) ? null : (E) queue[0]; |
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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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* precise control over the runtime type of the output array, and may, |
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* under certain circumstances, be used to save allocation costs. |
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* |
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* <p>Suppose <tt>x</tt> is a queue known to contain only strings. |
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* <p>Suppose {@code x} is a queue known to contain only strings. |
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* The following code can be used to dump the queue into a newly |
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* allocated array of <tt>String</tt>: |
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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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* |
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* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
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* <tt>toArray()</tt>. |
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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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* |
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* @param a the array into which the elements of the queue are to |
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* be stored, if it is big enough; otherwise, a new array of the |
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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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(forgetMeNot != null && !forgetMeNot.isEmpty()); |
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} |
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|
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@SuppressWarnings("unchecked") |
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public E next() { |
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if (expectedModCount != modCount) |
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throw new ConcurrentModificationException(); |
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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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size = 0; |
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} |
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|
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@SuppressWarnings("unchecked") |
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public E poll() { |
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if (size == 0) |
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return null; |
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* position before i. This fact is used by iterator.remove so as to |
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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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assert i >= 0 && i < size; |
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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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if (s == i) // removed last element |
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siftUpComparable(k, x); |
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} |
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@SuppressWarnings("unchecked") |
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private void siftUpComparable(int k, E x) { |
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Comparable<? super E> key = (Comparable<? super E>) x; |
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while (k > 0) { |
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queue[k] = key; |
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} |
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@SuppressWarnings("unchecked") |
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private void siftUpUsingComparator(int k, E x) { |
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while (k > 0) { |
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int parent = (k - 1) >>> 1; |
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siftDownComparable(k, x); |
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} |
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@SuppressWarnings("unchecked") |
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private void siftDownComparable(int k, E x) { |
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Comparable<? super E> key = (Comparable<? super E>)x; |
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int half = size >>> 1; // loop while a non-leaf |
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queue[k] = key; |
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} |
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|
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@SuppressWarnings("unchecked") |
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private void siftDownUsingComparator(int k, E x) { |
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int half = size >>> 1; |
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while (k < half) { |
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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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*/ |
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@SuppressWarnings("unchecked") |
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private void heapify() { |
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for (int i = (size >>> 1) - 1; i >= 0; i--) |
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siftDown(i, (E) queue[i]); |
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} |
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/** |
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* Saves the state of the instance to a stream (that |
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* is, serializes it). |
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* Saves this queue to a stream (that is, serializes it). |
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* |
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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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* @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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throws java.io.IOException { |
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// Write out element count, and any hidden stuff |
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s.defaultWriteObject(); |
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|
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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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// spec has never explained what that might be. |
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heapify(); |
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} |
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|
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public Spliterator<E> spliterator() { |
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return new PriorityQueueSpliterator<E>(this, 0, -1, 0); |
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} |
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|
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/** |
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* This is very similar to ArrayList Spliterator, except for extra |
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* null checks. |
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*/ |
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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 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(PriorityQueue<E> pq, int origin, int fence, |
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int expectedModCount) { |
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this.pq = pq; |
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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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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 = pq.modCount; |
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hi = fence = pq.size; |
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} |
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return hi; |
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} |
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|
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public Spliterator<E> 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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} |
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|
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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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PriorityQueue<E> q; Object[] a; |
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if (action == null) |
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throw new NullPointerException(); |
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if ((q = pq) != null && (a = q.queue) != null) { |
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if ((hi = fence) < 0) { |
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mc = q.modCount; |
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hi = q.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 (q.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(Consumer<? super E> action) { |
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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)pq.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 (pq.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() { |
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return (long) (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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} |