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/* |
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* %W% %E% |
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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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* Copyright 2006 Sun Microsystems, Inc. All rights reserved. |
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* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
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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. Oracle designates this |
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* particular file as subject to the "Classpath" exception as provided |
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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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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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*/ |
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package java.util; |
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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 elements of the priority queue are ordered according to their |
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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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* ({@code peek}, {@code element}, and {@code size}). |
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* |
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* <p>This class is a member of the |
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* <a href="{@docRoot}/../guide/collections/index.html"> |
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* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
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* Java Collections Framework</a>. |
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* |
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* @since 1.5 |
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* @version %I%, %G% |
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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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* 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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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; // 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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* @throws NullPointerException if the specified collection or any |
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* of its elements are null |
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*/ |
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@SuppressWarnings("unchecked") |
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public PriorityQueue(Collection<? extends E> c) { |
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initFromCollection(c); |
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if (c instanceof SortedSet) |
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comparator = (Comparator<? super E>) |
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((SortedSet<? extends E>)c).comparator(); |
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else if (c instanceof PriorityQueue) |
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comparator = (Comparator<? super E>) |
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((PriorityQueue<? extends E>)c).comparator(); |
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if (c instanceof SortedSet<?>) { |
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SortedSet<? extends E> ss = (SortedSet<? extends E>) c; |
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this.comparator = (Comparator<? super E>) ss.comparator(); |
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initElementsFromCollection(ss); |
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} |
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else if (c instanceof PriorityQueue<?>) { |
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PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c; |
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this.comparator = (Comparator<? super E>) pq.comparator(); |
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initFromPriorityQueue(pq); |
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} |
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else { |
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comparator = null; |
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heapify(); |
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this.comparator = null; |
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initFromCollection(c); |
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} |
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} |
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|
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* @throws NullPointerException if the specified priority queue or any |
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* of its elements are null |
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*/ |
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@SuppressWarnings("unchecked") |
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public PriorityQueue(PriorityQueue<? extends E> c) { |
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comparator = (Comparator<? super E>)c.comparator(); |
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initFromCollection(c); |
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this.comparator = (Comparator<? super E>) c.comparator(); |
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initFromPriorityQueue(c); |
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} |
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|
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/** |
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* @throws NullPointerException if the specified sorted set or any |
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* of its elements are null |
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*/ |
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@SuppressWarnings("unchecked") |
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public PriorityQueue(SortedSet<? extends E> c) { |
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comparator = (Comparator<? super E>)c.comparator(); |
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initFromCollection(c); |
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this.comparator = (Comparator<? super E>) c.comparator(); |
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initElementsFromCollection(c); |
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} |
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|
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private void initFromPriorityQueue(PriorityQueue<? extends E> c) { |
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if (c.getClass() == PriorityQueue.class) { |
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this.queue = c.toArray(); |
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this.size = c.size(); |
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} else { |
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initFromCollection(c); |
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} |
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} |
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|
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private void initElementsFromCollection(Collection<? extends E> c) { |
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Object[] a = c.toArray(); |
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// If c.toArray incorrectly doesn't return Object[], copy it. |
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if (a.getClass() != Object[].class) |
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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 (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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} |
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|
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/** |
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* @param c the collection |
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*/ |
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private void initFromCollection(Collection<? extends E> c) { |
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Object[] a = c.toArray(); |
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// If c.toArray incorrectly doesn't return Object[], copy it. |
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if (a.getClass() != Object[].class) |
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a = Arrays.copyOf(a, a.length, Object[].class); |
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queue = a; |
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size = a.length; |
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initElementsFromCollection(c); |
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heapify(); |
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} |
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|
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/** |
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* The maximum size of array to allocate. |
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* Some VMs reserve some header words in an array. |
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* Attempts to allocate larger arrays may result in |
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* OutOfMemoryError: Requested array size exceeds VM limit |
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*/ |
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private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; |
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|
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/** |
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* Increases the capacity of the array. |
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* |
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* @param minCapacity the desired minimum capacity |
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*/ |
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private void grow(int minCapacity) { |
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if (minCapacity < 0) // overflow |
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throw new OutOfMemoryError(); |
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int oldCapacity = queue.length; |
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int oldCapacity = queue.length; |
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// Double size if small; else grow by 50% |
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int newCapacity = ((oldCapacity < 64)? |
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((oldCapacity + 1) * 2): |
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((oldCapacity / 2) * 3)); |
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if (newCapacity < 0) // overflow |
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newCapacity = Integer.MAX_VALUE; |
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if (newCapacity < minCapacity) |
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newCapacity = minCapacity; |
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int newCapacity = oldCapacity + ((oldCapacity < 64) ? |
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(oldCapacity + 2) : |
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(oldCapacity >> 1)); |
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// overflow-conscious code |
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if (newCapacity - MAX_ARRAY_SIZE > 0) |
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newCapacity = hugeCapacity(minCapacity); |
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queue = Arrays.copyOf(queue, newCapacity); |
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} |
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|
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private static int hugeCapacity(int minCapacity) { |
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if (minCapacity < 0) // overflow |
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throw new OutOfMemoryError(); |
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return (minCapacity > MAX_ARRAY_SIZE) ? |
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Integer.MAX_VALUE : |
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MAX_ARRAY_SIZE; |
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} |
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|
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/** |
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* Inserts the specified element into this priority queue. |
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* |
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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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if (size == 0) |
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return null; |
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return (E) queue[0]; |
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return (size == 0) ? null : (E) queue[0]; |
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} |
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|
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private int indexOf(Object o) { |
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if (o != null) { |
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if (o != null) { |
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for (int i = 0; i < size; i++) |
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if (o.equals(queue[i])) |
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return i; |
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* @return {@code true} if this queue changed as a result of the call |
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*/ |
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public boolean remove(Object o) { |
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int i = indexOf(o); |
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if (i == -1) |
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return false; |
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else { |
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removeAt(i); |
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return true; |
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} |
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int i = indexOf(o); |
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if (i == -1) |
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return false; |
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else { |
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removeAt(i); |
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return true; |
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} |
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} |
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|
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/** |
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* @return {@code true} if removed |
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*/ |
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boolean removeEq(Object o) { |
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for (int i = 0; i < size; i++) { |
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if (o == queue[i]) { |
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for (int i = 0; i < size; i++) { |
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if (o == queue[i]) { |
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removeAt(i); |
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return true; |
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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> |
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* 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 <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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< |
System.arraycopy(queue, 0, a, 0, size); |
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> |
System.arraycopy(queue, 0, a, 0, size); |
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if (a.length > size) |
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a[size] = null; |
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return a; |
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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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*/ |
512 |
< |
private ArrayDeque<E> forgetMeNot = null; |
512 |
> |
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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lastRetElt = null; |
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} else { |
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throw new IllegalStateException(); |
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< |
} |
565 |
> |
} |
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expectedModCount = modCount; |
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} |
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} |
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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() { |
587 |
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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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< |
private E removeAt(int i) { |
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< |
assert i >= 0 && i < size; |
611 |
> |
@SuppressWarnings("unchecked") |
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> |
E removeAt(int i) { |
613 |
> |
// assert i >= 0 && i < size; |
614 |
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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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|
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+ |
@SuppressWarnings("unchecked") |
651 |
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private void siftUpComparable(int k, E x) { |
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Comparable<? super E> key = (Comparable<? super E>) x; |
653 |
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while (k > 0) { |
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queue[k] = key; |
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} |
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|
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+ |
@SuppressWarnings("unchecked") |
665 |
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private void siftUpUsingComparator(int k, E x) { |
666 |
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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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|
|
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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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} |
710 |
|
|
711 |
+ |
@SuppressWarnings("unchecked") |
712 |
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private void siftDownUsingComparator(int k, E x) { |
713 |
|
int half = size >>> 1; |
714 |
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while (k < half) { |
730 |
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* Establishes the heap invariant (described above) in the entire tree, |
731 |
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* assuming nothing about the order of the elements prior to the call. |
732 |
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*/ |
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+ |
@SuppressWarnings("unchecked") |
734 |
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private void heapify() { |
735 |
|
for (int i = (size >>> 1) - 1; i >= 0; i--) |
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siftDown(i, (E) queue[i]); |
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} |
751 |
|
|
752 |
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/** |
753 |
< |
* Saves the state of the instance to a stream (that |
676 |
< |
* is, serializes it). |
753 |
> |
* Saves this queue to a stream (that is, serializes it). |
754 |
|
* |
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* @serialData The length of the array backing the instance is |
756 |
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* emitted (int), followed by all of its elements |
757 |
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* (each an {@code Object}) in the proper order. |
758 |
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* @param s the stream |
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+ |
* @throws java.io.IOException if an I/O error occurs |
760 |
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*/ |
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 |
|
|
766 |
|
// Write out array length, for compatibility with 1.5 version |
767 |
|
s.writeInt(Math.max(2, size + 1)); |
768 |
|
|
769 |
< |
// Write out all elements in the proper order. |
769 |
> |
// Write out all elements in the "proper order". |
770 |
|
for (int i = 0; i < size; i++) |
771 |
|
s.writeObject(queue[i]); |
772 |
|
} |
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 { |
788 |
|
// Read in (and discard) array length |
789 |
|
s.readInt(); |
790 |
|
|
791 |
< |
queue = new Object[size]; |
791 |
> |
queue = new Object[size]; |
792 |
|
|
793 |
< |
// Read in all elements in the proper order. |
793 |
> |
// Read in all elements. |
794 |
|
for (int i = 0; i < size; i++) |
795 |
|
queue[i] = s.readObject(); |
796 |
+ |
|
797 |
+ |
// Elements are guaranteed to be in "proper order", but the |
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 |
|
} |