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/* |
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* Copyright (c) 2003, 2018, 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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1.81 |
* 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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|
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import java.util.function.Consumer; |
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import jdk.internal.misc.SharedSecrets; |
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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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* {@linkplain Comparable natural ordering}, or by a {@link Comparator} |
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* provided at queue construction time, depending on which constructor is |
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* used. A priority queue does not permit {@code null} elements. |
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* A priority queue relying on natural ordering also does not permit |
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* insertion of non-comparable objects (doing so may result in |
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* {@code ClassCastException}). |
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* |
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* <p>The <em>head</em> of this queue is the <em>least</em> element |
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* with respect to the specified ordering. If multiple elements are |
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* tied for least value, the head is one of those elements -- ties are |
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* broken arbitrarily. The queue retrieval operations {@code poll}, |
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* {@code remove}, {@code peek}, and {@code element} access the |
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* element at the head of the queue. |
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* |
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* <p>A priority queue is unbounded, but has an internal |
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* <i>capacity</i> governing the size of an array used to store the |
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* elements on the queue. It is always at least as large as the queue |
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* size. As elements are added to a priority queue, its capacity |
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* grows automatically. The details of the growth policy are not |
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* specified. |
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* |
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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()} 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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* <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 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}/java/util/package-summary.html#CollectionsFramework"> |
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* Java Collections Framework</a>. |
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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 queue |
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*/ |
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@SuppressWarnings("unchecked") |
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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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private static final long serialVersionUID = -7720805057305804111L; |
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|
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private static final int DEFAULT_INITIAL_CAPACITY = 11; |
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|
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/** |
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* Priority queue represented as a balanced binary heap: the two |
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* children of queue[n] are queue[2*n+1] and queue[2*(n+1)]. The |
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* priority queue is ordered by comparator, or by the elements' |
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* natural ordering, if comparator is null: For each node n in the |
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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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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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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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* natural ordering. |
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*/ |
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private final Comparator<? super E> comparator; |
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|
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/** |
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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; // 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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* capacity (11) that orders its elements according to their |
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* {@linkplain Comparable natural ordering}. |
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*/ |
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public PriorityQueue() { |
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this(DEFAULT_INITIAL_CAPACITY, null); |
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} |
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|
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/** |
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* Creates a {@code PriorityQueue} with the specified initial |
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* capacity that orders its elements according to their |
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* {@linkplain Comparable natural ordering}. |
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* |
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* @param initialCapacity the initial capacity for this priority queue |
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* @throws IllegalArgumentException if {@code initialCapacity} is less |
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* than 1 |
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*/ |
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public PriorityQueue(int initialCapacity) { |
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this(initialCapacity, null); |
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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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* Creates a {@code PriorityQueue} with the specified initial capacity |
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1.2 |
* that orders its elements according to the specified comparator. |
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* |
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* @param initialCapacity the initial capacity for this priority queue |
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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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* @throws IllegalArgumentException if {@code initialCapacity} is |
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* less than 1 |
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*/ |
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public PriorityQueue(int initialCapacity, |
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Comparator<? super E> comparator) { |
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// Note: This restriction of at least one is not actually needed, |
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// but continues for 1.5 compatibility |
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if (initialCapacity < 1) |
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throw new IllegalArgumentException(); |
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this.queue = new Object[initialCapacity]; |
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this.comparator = comparator; |
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} |
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|
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/** |
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* Creates a {@code PriorityQueue} containing the elements in the |
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* specified collection. If the specified collection is an instance of |
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* a {@link SortedSet} or is another {@code PriorityQueue}, this |
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* priority queue will be ordered according to the same ordering. |
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* Otherwise, this priority queue will be ordered according to the |
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* {@linkplain Comparable natural ordering} of its elements. |
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* |
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* @param c the collection whose elements are to be placed |
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* into this priority queue |
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* @throws ClassCastException if elements of the specified collection |
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* cannot be compared to one another according to the priority |
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* queue's ordering |
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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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tim |
1.2 |
*/ |
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tim |
1.16 |
public PriorityQueue(Collection<? extends E> c) { |
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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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this.comparator = null; |
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initFromCollection(c); |
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1.2 |
} |
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} |
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/** |
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1.63 |
* Creates a {@code PriorityQueue} containing the elements in the |
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* specified priority queue. This priority queue will be |
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* ordered according to the same ordering as the given priority |
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* queue. |
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* |
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* @param c the priority queue whose elements are to be placed |
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* into this priority queue |
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jsr166 |
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* @throws ClassCastException if elements of {@code c} cannot be |
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* compared to one another according to {@code c}'s |
218 |
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* ordering |
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* @throws NullPointerException if the specified priority queue or any |
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* of its elements are null |
221 |
dl |
1.22 |
*/ |
222 |
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public PriorityQueue(PriorityQueue<? extends E> c) { |
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1.70 |
this.comparator = (Comparator<? super E>) c.comparator(); |
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initFromPriorityQueue(c); |
225 |
dl |
1.22 |
} |
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dholmes |
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|
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dl |
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/** |
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jsr166 |
1.63 |
* Creates a {@code PriorityQueue} containing the elements in the |
229 |
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* specified sorted set. This priority queue will be ordered |
230 |
dl |
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* according to the same ordering as the given sorted set. |
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* |
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* @param c the sorted set whose elements are to be placed |
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1.63 |
* into this priority queue |
234 |
dl |
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* @throws ClassCastException if elements of the specified sorted |
235 |
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* set cannot be compared to one another according to the |
236 |
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* sorted set's ordering |
237 |
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* @throws NullPointerException if the specified sorted set or any |
238 |
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* of its elements are null |
239 |
dl |
1.22 |
*/ |
240 |
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public PriorityQueue(SortedSet<? extends E> 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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jsr166 |
1.125 |
/** Ensures that queue[0] exists, helping peek() and poll(). */ |
246 |
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private static Object[] ensureNonEmpty(Object[] es) { |
247 |
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return (es.length > 0) ? es : new Object[1]; |
248 |
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} |
249 |
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|
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jsr166 |
1.70 |
private void initFromPriorityQueue(PriorityQueue<? extends E> c) { |
251 |
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if (c.getClass() == PriorityQueue.class) { |
252 |
jsr166 |
1.125 |
this.queue = ensureNonEmpty(c.toArray()); |
253 |
jsr166 |
1.70 |
this.size = c.size(); |
254 |
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} else { |
255 |
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initFromCollection(c); |
256 |
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} |
257 |
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} |
258 |
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|
259 |
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private void initElementsFromCollection(Collection<? extends E> c) { |
260 |
jsr166 |
1.124 |
Object[] es = c.toArray(); |
261 |
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int len = es.length; |
262 |
jsr166 |
1.70 |
// If c.toArray incorrectly doesn't return Object[], copy it. |
263 |
jsr166 |
1.124 |
if (es.getClass() != Object[].class) |
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es = Arrays.copyOf(es, len, Object[].class); |
265 |
jsr166 |
1.70 |
if (len == 1 || this.comparator != null) |
266 |
jsr166 |
1.124 |
for (Object e : es) |
267 |
jsr166 |
1.106 |
if (e == null) |
268 |
jsr166 |
1.70 |
throw new NullPointerException(); |
269 |
jsr166 |
1.125 |
this.queue = ensureNonEmpty(es); |
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jsr166 |
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this.size = len; |
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tim |
1.1 |
} |
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|
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dl |
1.22 |
/** |
274 |
jsr166 |
1.63 |
* Initializes queue array with elements from the given Collection. |
275 |
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* |
276 |
dl |
1.55 |
* @param c the collection |
277 |
dl |
1.22 |
*/ |
278 |
dl |
1.55 |
private void initFromCollection(Collection<? extends E> c) { |
279 |
jsr166 |
1.70 |
initElementsFromCollection(c); |
280 |
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heapify(); |
281 |
jsr166 |
1.56 |
} |
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dl |
1.55 |
|
283 |
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/** |
284 |
jsr166 |
1.70 |
* The maximum size of array to allocate. |
285 |
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* Some VMs reserve some header words in an array. |
286 |
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* Attempts to allocate larger arrays may result in |
287 |
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* OutOfMemoryError: Requested array size exceeds VM limit |
288 |
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*/ |
289 |
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private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; |
290 |
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|
291 |
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/** |
292 |
dl |
1.55 |
* Increases the capacity of the array. |
293 |
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* |
294 |
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* @param minCapacity the desired minimum capacity |
295 |
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*/ |
296 |
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private void grow(int minCapacity) { |
297 |
jsr166 |
1.68 |
int oldCapacity = queue.length; |
298 |
dl |
1.55 |
// Double size if small; else grow by 50% |
299 |
jsr166 |
1.70 |
int newCapacity = oldCapacity + ((oldCapacity < 64) ? |
300 |
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(oldCapacity + 2) : |
301 |
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(oldCapacity >> 1)); |
302 |
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// overflow-conscious code |
303 |
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if (newCapacity - MAX_ARRAY_SIZE > 0) |
304 |
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newCapacity = hugeCapacity(minCapacity); |
305 |
dl |
1.55 |
queue = Arrays.copyOf(queue, newCapacity); |
306 |
dl |
1.22 |
} |
307 |
dl |
1.36 |
|
308 |
jsr166 |
1.70 |
private static int hugeCapacity(int minCapacity) { |
309 |
|
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if (minCapacity < 0) // overflow |
310 |
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throw new OutOfMemoryError(); |
311 |
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return (minCapacity > MAX_ARRAY_SIZE) ? |
312 |
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Integer.MAX_VALUE : |
313 |
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MAX_ARRAY_SIZE; |
314 |
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} |
315 |
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|
316 |
tim |
1.2 |
/** |
317 |
dl |
1.42 |
* Inserts the specified element into this priority queue. |
318 |
tim |
1.2 |
* |
319 |
jsr166 |
1.63 |
* @return {@code true} (as specified by {@link Collection#add}) |
320 |
dl |
1.52 |
* @throws ClassCastException if the specified element cannot be |
321 |
|
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* compared with elements currently in this priority queue |
322 |
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* according to the priority queue's ordering |
323 |
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* @throws NullPointerException if the specified element is null |
324 |
tim |
1.2 |
*/ |
325 |
dl |
1.52 |
public boolean add(E e) { |
326 |
|
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return offer(e); |
327 |
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} |
328 |
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|
329 |
|
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/** |
330 |
|
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* Inserts the specified element into this priority queue. |
331 |
|
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* |
332 |
jsr166 |
1.63 |
* @return {@code true} (as specified by {@link Queue#offer}) |
333 |
dl |
1.52 |
* @throws ClassCastException if the specified element cannot be |
334 |
|
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* compared with elements currently in this priority queue |
335 |
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* according to the priority queue's ordering |
336 |
|
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* @throws NullPointerException if the specified element is null |
337 |
|
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*/ |
338 |
|
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public boolean offer(E e) { |
339 |
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if (e == null) |
340 |
dholmes |
1.11 |
throw new NullPointerException(); |
341 |
|
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modCount++; |
342 |
dl |
1.55 |
int i = size; |
343 |
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if (i >= queue.length) |
344 |
|
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grow(i + 1); |
345 |
jsr166 |
1.109 |
siftUp(i, e); |
346 |
dl |
1.55 |
size = i + 1; |
347 |
dholmes |
1.11 |
return true; |
348 |
|
|
} |
349 |
|
|
|
350 |
dl |
1.40 |
public E peek() { |
351 |
jsr166 |
1.125 |
return (E) queue[0]; |
352 |
tim |
1.1 |
} |
353 |
|
|
|
354 |
dl |
1.52 |
private int indexOf(Object o) { |
355 |
jsr166 |
1.68 |
if (o != null) { |
356 |
jsr166 |
1.123 |
final Object[] es = queue; |
357 |
|
|
for (int i = 0, n = size; i < n; i++) |
358 |
|
|
if (o.equals(es[i])) |
359 |
dl |
1.55 |
return i; |
360 |
|
|
} |
361 |
dl |
1.52 |
return -1; |
362 |
|
|
} |
363 |
|
|
|
364 |
|
|
/** |
365 |
|
|
* Removes a single instance of the specified element from this queue, |
366 |
jsr166 |
1.63 |
* if it is present. More formally, removes an element {@code e} such |
367 |
|
|
* that {@code o.equals(e)}, if this queue contains one or more such |
368 |
|
|
* elements. Returns {@code true} if and only if this queue contained |
369 |
|
|
* the specified element (or equivalently, if this queue changed as a |
370 |
|
|
* result of the call). |
371 |
dl |
1.52 |
* |
372 |
|
|
* @param o element to be removed from this queue, if present |
373 |
jsr166 |
1.63 |
* @return {@code true} if this queue changed as a result of the call |
374 |
dl |
1.52 |
*/ |
375 |
|
|
public boolean remove(Object o) { |
376 |
jsr166 |
1.68 |
int i = indexOf(o); |
377 |
|
|
if (i == -1) |
378 |
|
|
return false; |
379 |
|
|
else { |
380 |
|
|
removeAt(i); |
381 |
|
|
return true; |
382 |
|
|
} |
383 |
dl |
1.52 |
} |
384 |
dholmes |
1.11 |
|
385 |
jsr166 |
1.56 |
/** |
386 |
jsr166 |
1.123 |
* Identity-based version for use in Itr.remove. |
387 |
jsr166 |
1.56 |
* |
388 |
dl |
1.55 |
* @param o element to be removed from this queue, if present |
389 |
|
|
*/ |
390 |
jsr166 |
1.123 |
void removeEq(Object o) { |
391 |
|
|
final Object[] es = queue; |
392 |
|
|
for (int i = 0, n = size; i < n; i++) { |
393 |
|
|
if (o == es[i]) { |
394 |
dl |
1.55 |
removeAt(i); |
395 |
jsr166 |
1.123 |
break; |
396 |
dl |
1.55 |
} |
397 |
|
|
} |
398 |
|
|
} |
399 |
|
|
|
400 |
dholmes |
1.11 |
/** |
401 |
jsr166 |
1.63 |
* Returns {@code true} if this queue contains the specified element. |
402 |
|
|
* More formally, returns {@code true} if and only if this queue contains |
403 |
|
|
* at least one element {@code e} such that {@code o.equals(e)}. |
404 |
dholmes |
1.23 |
* |
405 |
dl |
1.52 |
* @param o object to be checked for containment in this queue |
406 |
jsr166 |
1.63 |
* @return {@code true} if this queue contains the specified element |
407 |
dholmes |
1.11 |
*/ |
408 |
dl |
1.52 |
public boolean contains(Object o) { |
409 |
jsr166 |
1.100 |
return indexOf(o) >= 0; |
410 |
tim |
1.14 |
} |
411 |
dholmes |
1.11 |
|
412 |
dl |
1.49 |
/** |
413 |
jsr166 |
1.63 |
* Returns an array containing all of the elements in this queue. |
414 |
dl |
1.52 |
* The elements are in no particular order. |
415 |
|
|
* |
416 |
|
|
* <p>The returned array will be "safe" in that no references to it are |
417 |
jsr166 |
1.63 |
* maintained by this queue. (In other words, this method must allocate |
418 |
dl |
1.52 |
* a new array). The caller is thus free to modify the returned array. |
419 |
|
|
* |
420 |
jsr166 |
1.63 |
* <p>This method acts as bridge between array-based and collection-based |
421 |
|
|
* APIs. |
422 |
|
|
* |
423 |
jsr166 |
1.59 |
* @return an array containing all of the elements in this queue |
424 |
dl |
1.49 |
*/ |
425 |
dl |
1.52 |
public Object[] toArray() { |
426 |
dl |
1.55 |
return Arrays.copyOf(queue, size); |
427 |
dl |
1.52 |
} |
428 |
tim |
1.2 |
|
429 |
dl |
1.52 |
/** |
430 |
jsr166 |
1.63 |
* Returns an array containing all of the elements in this queue; the |
431 |
|
|
* runtime type of the returned array is that of the specified array. |
432 |
|
|
* The returned array elements are in no particular order. |
433 |
|
|
* If the queue fits in the specified array, it is returned therein. |
434 |
|
|
* Otherwise, a new array is allocated with the runtime type of the |
435 |
|
|
* specified array and the size of this queue. |
436 |
dl |
1.52 |
* |
437 |
|
|
* <p>If the queue fits in the specified array with room to spare |
438 |
|
|
* (i.e., the array has more elements than the queue), the element in |
439 |
|
|
* the array immediately following the end of the collection is set to |
440 |
jsr166 |
1.63 |
* {@code null}. |
441 |
|
|
* |
442 |
|
|
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
443 |
|
|
* array-based and collection-based APIs. Further, this method allows |
444 |
|
|
* precise control over the runtime type of the output array, and may, |
445 |
|
|
* under certain circumstances, be used to save allocation costs. |
446 |
|
|
* |
447 |
jsr166 |
1.80 |
* <p>Suppose {@code x} is a queue known to contain only strings. |
448 |
jsr166 |
1.63 |
* The following code can be used to dump the queue into a newly |
449 |
jsr166 |
1.80 |
* allocated array of {@code String}: |
450 |
jsr166 |
1.63 |
* |
451 |
jsr166 |
1.104 |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
452 |
jsr166 |
1.63 |
* |
453 |
jsr166 |
1.80 |
* Note that {@code toArray(new Object[0])} is identical in function to |
454 |
|
|
* {@code toArray()}. |
455 |
dl |
1.52 |
* |
456 |
|
|
* @param a the array into which the elements of the queue are to |
457 |
|
|
* be stored, if it is big enough; otherwise, a new array of the |
458 |
|
|
* same runtime type is allocated for this purpose. |
459 |
jsr166 |
1.63 |
* @return an array containing all of the elements in this queue |
460 |
dl |
1.52 |
* @throws ArrayStoreException if the runtime type of the specified array |
461 |
|
|
* is not a supertype of the runtime type of every element in |
462 |
|
|
* this queue |
463 |
|
|
* @throws NullPointerException if the specified array is null |
464 |
|
|
*/ |
465 |
|
|
public <T> T[] toArray(T[] a) { |
466 |
jsr166 |
1.85 |
final int size = this.size; |
467 |
dl |
1.52 |
if (a.length < size) |
468 |
|
|
// Make a new array of a's runtime type, but my contents: |
469 |
dl |
1.55 |
return (T[]) Arrays.copyOf(queue, size, a.getClass()); |
470 |
jsr166 |
1.68 |
System.arraycopy(queue, 0, a, 0, size); |
471 |
dl |
1.52 |
if (a.length > size) |
472 |
|
|
a[size] = null; |
473 |
|
|
return a; |
474 |
tim |
1.1 |
} |
475 |
tim |
1.2 |
|
476 |
dholmes |
1.23 |
/** |
477 |
|
|
* Returns an iterator over the elements in this queue. The iterator |
478 |
|
|
* does not return the elements in any particular order. |
479 |
|
|
* |
480 |
dl |
1.52 |
* @return an iterator over the elements in this queue |
481 |
dholmes |
1.23 |
*/ |
482 |
tim |
1.2 |
public Iterator<E> iterator() { |
483 |
dl |
1.7 |
return new Itr(); |
484 |
tim |
1.2 |
} |
485 |
|
|
|
486 |
dl |
1.55 |
private final class Itr implements Iterator<E> { |
487 |
dl |
1.7 |
/** |
488 |
|
|
* Index (into queue array) of element to be returned by |
489 |
tim |
1.2 |
* subsequent call to next. |
490 |
dl |
1.7 |
*/ |
491 |
jsr166 |
1.99 |
private int cursor; |
492 |
tim |
1.2 |
|
493 |
dl |
1.7 |
/** |
494 |
dl |
1.36 |
* Index of element returned by most recent call to next, |
495 |
|
|
* unless that element came from the forgetMeNot list. |
496 |
dl |
1.55 |
* Set to -1 if element is deleted by a call to remove. |
497 |
dl |
1.7 |
*/ |
498 |
dl |
1.55 |
private int lastRet = -1; |
499 |
dl |
1.7 |
|
500 |
|
|
/** |
501 |
dl |
1.55 |
* A queue of elements that were moved from the unvisited portion of |
502 |
dl |
1.36 |
* the heap into the visited portion as a result of "unlucky" element |
503 |
|
|
* removals during the iteration. (Unlucky element removals are those |
504 |
dl |
1.55 |
* that require a siftup instead of a siftdown.) We must visit all of |
505 |
dl |
1.36 |
* the elements in this list to complete the iteration. We do this |
506 |
|
|
* after we've completed the "normal" iteration. |
507 |
|
|
* |
508 |
|
|
* We expect that most iterations, even those involving removals, |
509 |
jsr166 |
1.63 |
* will not need to store elements in this field. |
510 |
dl |
1.36 |
*/ |
511 |
jsr166 |
1.99 |
private ArrayDeque<E> forgetMeNot; |
512 |
dl |
1.36 |
|
513 |
|
|
/** |
514 |
|
|
* Element returned by the most recent call to next iff that |
515 |
|
|
* element was drawn from the forgetMeNot list. |
516 |
|
|
*/ |
517 |
jsr166 |
1.99 |
private E lastRetElt; |
518 |
dl |
1.55 |
|
519 |
|
|
/** |
520 |
|
|
* The modCount value that the iterator believes that the backing |
521 |
jsr166 |
1.63 |
* Queue should have. If this expectation is violated, the iterator |
522 |
dl |
1.55 |
* has detected concurrent modification. |
523 |
|
|
*/ |
524 |
|
|
private int expectedModCount = modCount; |
525 |
dl |
1.35 |
|
526 |
jsr166 |
1.117 |
Itr() {} // prevent access constructor creation |
527 |
|
|
|
528 |
dl |
1.7 |
public boolean hasNext() { |
529 |
jsr166 |
1.56 |
return cursor < size || |
530 |
dl |
1.55 |
(forgetMeNot != null && !forgetMeNot.isEmpty()); |
531 |
dl |
1.7 |
} |
532 |
|
|
|
533 |
|
|
public E next() { |
534 |
dl |
1.55 |
if (expectedModCount != modCount) |
535 |
|
|
throw new ConcurrentModificationException(); |
536 |
jsr166 |
1.56 |
if (cursor < size) |
537 |
dl |
1.55 |
return (E) queue[lastRet = cursor++]; |
538 |
|
|
if (forgetMeNot != null) { |
539 |
|
|
lastRet = -1; |
540 |
|
|
lastRetElt = forgetMeNot.poll(); |
541 |
jsr166 |
1.56 |
if (lastRetElt != null) |
542 |
dl |
1.55 |
return lastRetElt; |
543 |
dl |
1.36 |
} |
544 |
dl |
1.55 |
throw new NoSuchElementException(); |
545 |
dl |
1.7 |
} |
546 |
tim |
1.2 |
|
547 |
dl |
1.7 |
public void remove() { |
548 |
dl |
1.55 |
if (expectedModCount != modCount) |
549 |
|
|
throw new ConcurrentModificationException(); |
550 |
|
|
if (lastRet != -1) { |
551 |
dl |
1.36 |
E moved = PriorityQueue.this.removeAt(lastRet); |
552 |
dl |
1.55 |
lastRet = -1; |
553 |
jsr166 |
1.56 |
if (moved == null) |
554 |
dl |
1.36 |
cursor--; |
555 |
dl |
1.55 |
else { |
556 |
dl |
1.36 |
if (forgetMeNot == null) |
557 |
dl |
1.89 |
forgetMeNot = new ArrayDeque<>(); |
558 |
dl |
1.36 |
forgetMeNot.add(moved); |
559 |
jsr166 |
1.56 |
} |
560 |
jsr166 |
1.63 |
} else if (lastRetElt != null) { |
561 |
dl |
1.55 |
PriorityQueue.this.removeEq(lastRetElt); |
562 |
dl |
1.36 |
lastRetElt = null; |
563 |
jsr166 |
1.63 |
} else { |
564 |
|
|
throw new IllegalStateException(); |
565 |
jsr166 |
1.68 |
} |
566 |
tim |
1.2 |
expectedModCount = modCount; |
567 |
dl |
1.7 |
} |
568 |
tim |
1.2 |
} |
569 |
|
|
|
570 |
tim |
1.1 |
public int size() { |
571 |
tim |
1.2 |
return size; |
572 |
tim |
1.1 |
} |
573 |
tim |
1.2 |
|
574 |
|
|
/** |
575 |
dl |
1.52 |
* Removes all of the elements from this priority queue. |
576 |
dl |
1.49 |
* The queue will be empty after this call returns. |
577 |
tim |
1.2 |
*/ |
578 |
|
|
public void clear() { |
579 |
|
|
modCount++; |
580 |
jsr166 |
1.123 |
final Object[] es = queue; |
581 |
|
|
for (int i = 0, n = size; i < n; i++) |
582 |
|
|
es[i] = null; |
583 |
tim |
1.2 |
size = 0; |
584 |
|
|
} |
585 |
|
|
|
586 |
dl |
1.40 |
public E poll() { |
587 |
jsr166 |
1.125 |
final Object[] es; |
588 |
|
|
final E result; |
589 |
|
|
|
590 |
|
|
if ((result = (E) ((es = queue)[0])) != null) { |
591 |
|
|
modCount++; |
592 |
|
|
final int n; |
593 |
|
|
final E x = (E) es[(n = --size)]; |
594 |
|
|
es[n] = null; |
595 |
|
|
if (n > 0) { |
596 |
|
|
final Comparator<? super E> cmp; |
597 |
|
|
if ((cmp = comparator) == null) |
598 |
|
|
siftDownComparable(0, x, es, n); |
599 |
|
|
else |
600 |
|
|
siftDownUsingComparator(0, x, es, n, cmp); |
601 |
|
|
} |
602 |
|
|
} |
603 |
dl |
1.36 |
return result; |
604 |
|
|
} |
605 |
|
|
|
606 |
|
|
/** |
607 |
dl |
1.55 |
* Removes the ith element from queue. |
608 |
tim |
1.2 |
* |
609 |
dl |
1.55 |
* Normally this method leaves the elements at up to i-1, |
610 |
|
|
* inclusive, untouched. Under these circumstances, it returns |
611 |
|
|
* null. Occasionally, in order to maintain the heap invariant, |
612 |
|
|
* it must swap a later element of the list with one earlier than |
613 |
|
|
* i. Under these circumstances, this method returns the element |
614 |
|
|
* that was previously at the end of the list and is now at some |
615 |
|
|
* position before i. This fact is used by iterator.remove so as to |
616 |
jsr166 |
1.63 |
* avoid missing traversing elements. |
617 |
tim |
1.2 |
*/ |
618 |
jsr166 |
1.107 |
E removeAt(int i) { |
619 |
jsr166 |
1.74 |
// assert i >= 0 && i < size; |
620 |
jsr166 |
1.126 |
final Object[] es = queue; |
621 |
tim |
1.2 |
modCount++; |
622 |
dl |
1.55 |
int s = --size; |
623 |
|
|
if (s == i) // removed last element |
624 |
jsr166 |
1.126 |
es[i] = null; |
625 |
dl |
1.55 |
else { |
626 |
|
|
E moved = (E) queue[s]; |
627 |
jsr166 |
1.126 |
es[s] = null; |
628 |
dl |
1.55 |
siftDown(i, moved); |
629 |
jsr166 |
1.126 |
if (es[i] == moved) { |
630 |
dl |
1.55 |
siftUp(i, moved); |
631 |
jsr166 |
1.126 |
if (es[i] != moved) |
632 |
dl |
1.36 |
return moved; |
633 |
|
|
} |
634 |
dl |
1.35 |
} |
635 |
dl |
1.36 |
return null; |
636 |
tim |
1.1 |
} |
637 |
|
|
|
638 |
tim |
1.2 |
/** |
639 |
dl |
1.55 |
* Inserts item x at position k, maintaining heap invariant by |
640 |
|
|
* promoting x up the tree until it is greater than or equal to |
641 |
|
|
* its parent, or is the root. |
642 |
|
|
* |
643 |
jsr166 |
1.116 |
* To simplify and speed up coercions and comparisons, the |
644 |
dl |
1.55 |
* Comparable and Comparator versions are separated into different |
645 |
|
|
* methods that are otherwise identical. (Similarly for siftDown.) |
646 |
jsr166 |
1.56 |
* |
647 |
dl |
1.55 |
* @param k the position to fill |
648 |
|
|
* @param x the item to insert |
649 |
|
|
*/ |
650 |
|
|
private void siftUp(int k, E x) { |
651 |
jsr166 |
1.56 |
if (comparator != null) |
652 |
jsr166 |
1.124 |
siftUpUsingComparator(k, x, queue, comparator); |
653 |
dl |
1.55 |
else |
654 |
jsr166 |
1.124 |
siftUpComparable(k, x, queue); |
655 |
dl |
1.55 |
} |
656 |
|
|
|
657 |
jsr166 |
1.124 |
private static <T> void siftUpComparable(int k, T x, Object[] es) { |
658 |
|
|
Comparable<? super T> key = (Comparable<? super T>) x; |
659 |
dl |
1.55 |
while (k > 0) { |
660 |
|
|
int parent = (k - 1) >>> 1; |
661 |
jsr166 |
1.124 |
Object e = es[parent]; |
662 |
|
|
if (key.compareTo((T) e) >= 0) |
663 |
dl |
1.55 |
break; |
664 |
jsr166 |
1.124 |
es[k] = e; |
665 |
dl |
1.55 |
k = parent; |
666 |
|
|
} |
667 |
jsr166 |
1.124 |
es[k] = key; |
668 |
dl |
1.55 |
} |
669 |
|
|
|
670 |
jsr166 |
1.124 |
private static <T> void siftUpUsingComparator( |
671 |
|
|
int k, T x, Object[] es, Comparator<? super T> cmp) { |
672 |
dl |
1.55 |
while (k > 0) { |
673 |
|
|
int parent = (k - 1) >>> 1; |
674 |
jsr166 |
1.124 |
Object e = es[parent]; |
675 |
|
|
if (cmp.compare(x, (T) e) >= 0) |
676 |
dl |
1.55 |
break; |
677 |
jsr166 |
1.124 |
es[k] = e; |
678 |
dl |
1.55 |
k = parent; |
679 |
|
|
} |
680 |
jsr166 |
1.124 |
es[k] = x; |
681 |
dl |
1.55 |
} |
682 |
|
|
|
683 |
|
|
/** |
684 |
|
|
* Inserts item x at position k, maintaining heap invariant by |
685 |
|
|
* demoting x down the tree repeatedly until it is less than or |
686 |
|
|
* equal to its children or is a leaf. |
687 |
|
|
* |
688 |
|
|
* @param k the position to fill |
689 |
|
|
* @param x the item to insert |
690 |
|
|
*/ |
691 |
|
|
private void siftDown(int k, E x) { |
692 |
jsr166 |
1.56 |
if (comparator != null) |
693 |
jsr166 |
1.124 |
siftDownUsingComparator(k, x, queue, size, comparator); |
694 |
dl |
1.55 |
else |
695 |
jsr166 |
1.124 |
siftDownComparable(k, x, queue, size); |
696 |
dl |
1.55 |
} |
697 |
|
|
|
698 |
jsr166 |
1.124 |
private static <T> void siftDownComparable(int k, T x, Object[] es, int n) { |
699 |
|
|
// assert n > 0; |
700 |
|
|
Comparable<? super T> key = (Comparable<? super T>)x; |
701 |
|
|
int half = n >>> 1; // loop while a non-leaf |
702 |
dl |
1.55 |
while (k < half) { |
703 |
|
|
int child = (k << 1) + 1; // assume left child is least |
704 |
jsr166 |
1.124 |
Object c = es[child]; |
705 |
dl |
1.55 |
int right = child + 1; |
706 |
jsr166 |
1.124 |
if (right < n && |
707 |
|
|
((Comparable<? super T>) c).compareTo((T) es[right]) > 0) |
708 |
|
|
c = es[child = right]; |
709 |
|
|
if (key.compareTo((T) c) <= 0) |
710 |
dl |
1.55 |
break; |
711 |
jsr166 |
1.124 |
es[k] = c; |
712 |
dl |
1.55 |
k = child; |
713 |
|
|
} |
714 |
jsr166 |
1.124 |
es[k] = key; |
715 |
dl |
1.55 |
} |
716 |
|
|
|
717 |
jsr166 |
1.124 |
private static <T> void siftDownUsingComparator( |
718 |
|
|
int k, T x, Object[] es, int n, Comparator<? super T> cmp) { |
719 |
|
|
// assert n > 0; |
720 |
|
|
int half = n >>> 1; |
721 |
dl |
1.55 |
while (k < half) { |
722 |
|
|
int child = (k << 1) + 1; |
723 |
jsr166 |
1.124 |
Object c = es[child]; |
724 |
dl |
1.55 |
int right = child + 1; |
725 |
jsr166 |
1.124 |
if (right < n && cmp.compare((T) c, (T) es[right]) > 0) |
726 |
|
|
c = es[child = right]; |
727 |
|
|
if (cmp.compare(x, (T) c) <= 0) |
728 |
dl |
1.55 |
break; |
729 |
jsr166 |
1.124 |
es[k] = c; |
730 |
dl |
1.55 |
k = child; |
731 |
tim |
1.2 |
} |
732 |
jsr166 |
1.124 |
es[k] = x; |
733 |
dl |
1.36 |
} |
734 |
dl |
1.35 |
|
735 |
dl |
1.36 |
/** |
736 |
|
|
* Establishes the heap invariant (described above) in the entire tree, |
737 |
|
|
* assuming nothing about the order of the elements prior to the call. |
738 |
jsr166 |
1.112 |
* This classic algorithm due to Floyd (1964) is known to be O(size). |
739 |
dl |
1.36 |
*/ |
740 |
|
|
private void heapify() { |
741 |
jsr166 |
1.114 |
final Object[] es = queue; |
742 |
jsr166 |
1.124 |
int n = size, i = (n >>> 1) - 1; |
743 |
jsr166 |
1.125 |
final Comparator<? super E> cmp; |
744 |
|
|
if ((cmp = comparator) == null) |
745 |
jsr166 |
1.118 |
for (; i >= 0; i--) |
746 |
jsr166 |
1.124 |
siftDownComparable(i, (E) es[i], es, n); |
747 |
jsr166 |
1.114 |
else |
748 |
jsr166 |
1.118 |
for (; i >= 0; i--) |
749 |
jsr166 |
1.124 |
siftDownUsingComparator(i, (E) es[i], es, n, cmp); |
750 |
tim |
1.2 |
} |
751 |
|
|
|
752 |
dholmes |
1.23 |
/** |
753 |
dl |
1.52 |
* Returns the comparator used to order the elements in this |
754 |
jsr166 |
1.63 |
* queue, or {@code null} if this queue is sorted according to |
755 |
dl |
1.52 |
* the {@linkplain Comparable natural ordering} of its elements. |
756 |
|
|
* |
757 |
|
|
* @return the comparator used to order this queue, or |
758 |
jsr166 |
1.63 |
* {@code null} if this queue is sorted according to the |
759 |
|
|
* natural ordering of its elements |
760 |
dholmes |
1.23 |
*/ |
761 |
tim |
1.16 |
public Comparator<? super E> comparator() { |
762 |
tim |
1.2 |
return comparator; |
763 |
|
|
} |
764 |
dl |
1.5 |
|
765 |
|
|
/** |
766 |
jsr166 |
1.77 |
* Saves this queue to a stream (that is, serializes it). |
767 |
dl |
1.5 |
* |
768 |
jsr166 |
1.110 |
* @param s the stream |
769 |
|
|
* @throws java.io.IOException if an I/O error occurs |
770 |
dl |
1.5 |
* @serialData The length of the array backing the instance is |
771 |
jsr166 |
1.63 |
* emitted (int), followed by all of its elements |
772 |
|
|
* (each an {@code Object}) in the proper order. |
773 |
dl |
1.5 |
*/ |
774 |
dl |
1.22 |
private void writeObject(java.io.ObjectOutputStream s) |
775 |
jsr166 |
1.75 |
throws java.io.IOException { |
776 |
dl |
1.7 |
// Write out element count, and any hidden stuff |
777 |
|
|
s.defaultWriteObject(); |
778 |
dl |
1.5 |
|
779 |
jsr166 |
1.63 |
// Write out array length, for compatibility with 1.5 version |
780 |
|
|
s.writeInt(Math.max(2, size + 1)); |
781 |
dl |
1.5 |
|
782 |
jsr166 |
1.64 |
// Write out all elements in the "proper order". |
783 |
jsr166 |
1.123 |
final Object[] es = queue; |
784 |
|
|
for (int i = 0, n = size; i < n; i++) |
785 |
|
|
s.writeObject(es[i]); |
786 |
dl |
1.5 |
} |
787 |
|
|
|
788 |
|
|
/** |
789 |
dl |
1.81 |
* Reconstitutes the {@code PriorityQueue} instance from a stream |
790 |
|
|
* (that is, deserializes it). |
791 |
|
|
* |
792 |
|
|
* @param s the stream |
793 |
jsr166 |
1.97 |
* @throws ClassNotFoundException if the class of a serialized object |
794 |
|
|
* could not be found |
795 |
|
|
* @throws java.io.IOException if an I/O error occurs |
796 |
dl |
1.5 |
*/ |
797 |
dl |
1.22 |
private void readObject(java.io.ObjectInputStream s) |
798 |
dl |
1.5 |
throws java.io.IOException, ClassNotFoundException { |
799 |
dl |
1.7 |
// Read in size, and any hidden stuff |
800 |
|
|
s.defaultReadObject(); |
801 |
dl |
1.5 |
|
802 |
jsr166 |
1.63 |
// Read in (and discard) array length |
803 |
|
|
s.readInt(); |
804 |
|
|
|
805 |
jsr166 |
1.120 |
SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, size); |
806 |
jsr166 |
1.125 |
final Object[] es = queue = new Object[Math.max(size, 1)]; |
807 |
dl |
1.5 |
|
808 |
jsr166 |
1.64 |
// Read in all elements. |
809 |
jsr166 |
1.123 |
for (int i = 0, n = size; i < n; i++) |
810 |
|
|
es[i] = s.readObject(); |
811 |
jsr166 |
1.64 |
|
812 |
jsr166 |
1.68 |
// Elements are guaranteed to be in "proper order", but the |
813 |
|
|
// spec has never explained what that might be. |
814 |
|
|
heapify(); |
815 |
dl |
1.5 |
} |
816 |
dl |
1.81 |
|
817 |
jsr166 |
1.106 |
/** |
818 |
|
|
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em> |
819 |
|
|
* and <em>fail-fast</em> {@link Spliterator} over the elements in this |
820 |
jsr166 |
1.111 |
* queue. The spliterator does not traverse elements in any particular order |
821 |
|
|
* (the {@link Spliterator#ORDERED ORDERED} characteristic is not reported). |
822 |
jsr166 |
1.106 |
* |
823 |
|
|
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED}, |
824 |
|
|
* {@link Spliterator#SUBSIZED}, and {@link Spliterator#NONNULL}. |
825 |
|
|
* Overriding implementations should document the reporting of additional |
826 |
|
|
* characteristic values. |
827 |
|
|
* |
828 |
|
|
* @return a {@code Spliterator} over the elements in this queue |
829 |
|
|
* @since 1.8 |
830 |
|
|
*/ |
831 |
|
|
public final Spliterator<E> spliterator() { |
832 |
jsr166 |
1.113 |
return new PriorityQueueSpliterator(0, -1, 0); |
833 |
dl |
1.81 |
} |
834 |
|
|
|
835 |
jsr166 |
1.113 |
final class PriorityQueueSpliterator implements Spliterator<E> { |
836 |
dl |
1.89 |
private int index; // current index, modified on advance/split |
837 |
|
|
private int fence; // -1 until first use |
838 |
|
|
private int expectedModCount; // initialized when fence set |
839 |
dl |
1.81 |
|
840 |
jsr166 |
1.108 |
/** Creates new spliterator covering the given range. */ |
841 |
jsr166 |
1.113 |
PriorityQueueSpliterator(int origin, int fence, int expectedModCount) { |
842 |
dl |
1.89 |
this.index = origin; |
843 |
|
|
this.fence = fence; |
844 |
dl |
1.81 |
this.expectedModCount = expectedModCount; |
845 |
|
|
} |
846 |
|
|
|
847 |
dl |
1.89 |
private int getFence() { // initialize fence to size on first use |
848 |
|
|
int hi; |
849 |
|
|
if ((hi = fence) < 0) { |
850 |
jsr166 |
1.113 |
expectedModCount = modCount; |
851 |
|
|
hi = fence = size; |
852 |
dl |
1.89 |
} |
853 |
|
|
return hi; |
854 |
|
|
} |
855 |
jsr166 |
1.90 |
|
856 |
jsr166 |
1.113 |
public PriorityQueueSpliterator trySplit() { |
857 |
dl |
1.89 |
int hi = getFence(), lo = index, mid = (lo + hi) >>> 1; |
858 |
dl |
1.81 |
return (lo >= mid) ? null : |
859 |
jsr166 |
1.113 |
new PriorityQueueSpliterator(lo, index = mid, expectedModCount); |
860 |
dl |
1.81 |
} |
861 |
|
|
|
862 |
dl |
1.95 |
public void forEachRemaining(Consumer<? super E> action) { |
863 |
dl |
1.89 |
if (action == null) |
864 |
dl |
1.81 |
throw new NullPointerException(); |
865 |
jsr166 |
1.115 |
if (fence < 0) { fence = size; expectedModCount = modCount; } |
866 |
jsr166 |
1.124 |
final Object[] es = queue; |
867 |
jsr166 |
1.115 |
int i, hi; E e; |
868 |
|
|
for (i = index, index = hi = fence; i < hi; i++) { |
869 |
jsr166 |
1.124 |
if ((e = (E) es[i]) == null) |
870 |
jsr166 |
1.115 |
break; // must be CME |
871 |
|
|
action.accept(e); |
872 |
dl |
1.81 |
} |
873 |
jsr166 |
1.115 |
if (modCount != expectedModCount) |
874 |
|
|
throw new ConcurrentModificationException(); |
875 |
dl |
1.81 |
} |
876 |
|
|
|
877 |
dl |
1.89 |
public boolean tryAdvance(Consumer<? super E> action) { |
878 |
jsr166 |
1.106 |
if (action == null) |
879 |
|
|
throw new NullPointerException(); |
880 |
jsr166 |
1.115 |
if (fence < 0) { fence = size; expectedModCount = modCount; } |
881 |
|
|
int i; |
882 |
|
|
if ((i = index) < fence) { |
883 |
|
|
index = i + 1; |
884 |
|
|
E e; |
885 |
|
|
if ((e = (E) queue[i]) == null |
886 |
|
|
|| modCount != expectedModCount) |
887 |
dl |
1.89 |
throw new ConcurrentModificationException(); |
888 |
|
|
action.accept(e); |
889 |
dl |
1.81 |
return true; |
890 |
|
|
} |
891 |
|
|
return false; |
892 |
|
|
} |
893 |
|
|
|
894 |
jsr166 |
1.90 |
public long estimateSize() { |
895 |
jsr166 |
1.113 |
return getFence() - index; |
896 |
dl |
1.89 |
} |
897 |
|
|
|
898 |
|
|
public int characteristics() { |
899 |
|
|
return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL; |
900 |
|
|
} |
901 |
dl |
1.81 |
} |
902 |
jsr166 |
1.122 |
|
903 |
|
|
/** |
904 |
|
|
* @throws NullPointerException {@inheritDoc} |
905 |
|
|
*/ |
906 |
|
|
public void forEach(Consumer<? super E> action) { |
907 |
|
|
Objects.requireNonNull(action); |
908 |
|
|
final int expectedModCount = modCount; |
909 |
|
|
final Object[] es = queue; |
910 |
|
|
for (int i = 0, n = size; i < n; i++) |
911 |
|
|
action.accept((E) es[i]); |
912 |
|
|
if (expectedModCount != modCount) |
913 |
|
|
throw new ConcurrentModificationException(); |
914 |
|
|
} |
915 |
tim |
1.1 |
} |