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/* |
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* Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. 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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|
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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 java.util.function.Predicate; |
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// OPENJDK import jdk.internal.access.SharedSecrets; |
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import jdk.internal.util.ArraysSupport; |
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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.base/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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// OPENJDK @java.io.Serial |
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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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/** |
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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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* @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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*/ |
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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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} |
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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 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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* @throws ClassCastException if elements of {@code c} cannot be |
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* compared to one another according to {@code c}'s |
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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 |
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*/ |
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public PriorityQueue(PriorityQueue<? extends E> 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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* Creates a {@code PriorityQueue} containing the elements in the |
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* specified sorted set. This priority queue will be ordered |
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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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* into this priority queue |
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* @throws ClassCastException if elements of the specified sorted |
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* set cannot be compared to one another according to the |
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* sorted set's ordering |
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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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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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/** Ensures that queue[0] exists, helping peek() and poll(). */ |
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private static Object[] ensureNonEmpty(Object[] es) { |
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return (es.length > 0) ? es : new Object[1]; |
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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 = ensureNonEmpty(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[] es = c.toArray(); |
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int len = es.length; |
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// If c.toArray incorrectly doesn't return Object[], copy it. |
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if (es.getClass() != Object[].class) |
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es = Arrays.copyOf(es, len, Object[].class); |
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if (len == 1 || this.comparator != null) |
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for (Object e : es) |
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if (e == null) |
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throw new NullPointerException(); |
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this.queue = ensureNonEmpty(es); |
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this.size = len; |
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} |
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|
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/** |
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* Initializes queue array with elements from the given Collection. |
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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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initElementsFromCollection(c); |
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heapify(); |
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} |
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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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int oldCapacity = queue.length; |
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// Double size if small; else grow by 50% |
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int newCapacity = ArraysSupport.newLength(oldCapacity, |
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minCapacity - oldCapacity, /* minimum growth */ |
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oldCapacity < 64 ? oldCapacity + 2 : oldCapacity >> 1 |
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/* preferred growth */); |
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queue = Arrays.copyOf(queue, newCapacity); |
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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 {@code true} (as specified by {@link Collection#add}) |
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* @throws ClassCastException if the specified element cannot be |
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* compared with elements currently in this priority queue |
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* according to the priority queue's ordering |
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* @throws NullPointerException if the specified element is null |
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*/ |
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public boolean add(E e) { |
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return offer(e); |
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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 {@code true} (as specified by {@link Queue#offer}) |
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* @throws ClassCastException if the specified element cannot be |
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* compared with elements currently in this priority queue |
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* according to the priority queue's ordering |
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* @throws NullPointerException if the specified element is null |
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*/ |
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public boolean offer(E e) { |
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if (e == null) |
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throw new NullPointerException(); |
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modCount++; |
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int i = size; |
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if (i >= queue.length) |
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grow(i + 1); |
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siftUp(i, e); |
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size = i + 1; |
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return true; |
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} |
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|
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public E peek() { |
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return (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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final Object[] es = queue; |
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for (int i = 0, n = size; i < n; i++) |
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if (o.equals(es[i])) |
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return i; |
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} |
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return -1; |
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} |
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|
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/** |
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* Removes a single instance of the specified element from this queue, |
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* if it is present. More formally, removes an element {@code e} such |
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* that {@code o.equals(e)}, if this queue contains one or more such |
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* elements. Returns {@code true} if and only if this queue contained |
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* the specified element (or equivalently, if this queue changed as a |
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* result of the call). |
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* |
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* @param o element to be removed from this queue, if present |
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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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} |
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|
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/** |
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* Identity-based version for use in Itr.remove. |
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* |
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* @param o element to be removed from this queue, if present |
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*/ |
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void removeEq(Object o) { |
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final Object[] es = queue; |
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for (int i = 0, n = size; i < n; i++) { |
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if (o == es[i]) { |
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removeAt(i); |
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break; |
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} |
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} |
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} |
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|
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/** |
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* Returns {@code true} if this queue contains the specified element. |
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* More formally, returns {@code true} if and only if this queue contains |
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* at least one element {@code e} such that {@code o.equals(e)}. |
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* |
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* @param o object to be checked for containment in this queue |
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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) >= 0; |
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} |
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|
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/** |
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* Returns an array containing all of the elements in this queue. |
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* The elements are in no particular order. |
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* |
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* <p>The returned array will be "safe" in that no references to it are |
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* maintained by this queue. (In other words, this method must allocate |
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* a new array). The caller is thus free to modify the returned array. |
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* |
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* <p>This method acts as bridge between array-based and collection-based |
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* APIs. |
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* |
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* @return an array containing all of the elements in this queue |
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*/ |
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public Object[] toArray() { |
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return Arrays.copyOf(queue, size); |
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} |
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|
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/** |
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* Returns an array containing all of the elements in this queue; the |
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* runtime type of the returned array is that of the specified array. |
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* The returned array elements are in no particular order. |
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* If the queue fits in the specified array, it is returned therein. |
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* Otherwise, a new array is allocated with the runtime type of the |
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* specified array and the size of this queue. |
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* |
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* <p>If the queue fits in the specified array with room to spare |
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* (i.e., the array has more elements than the queue), the element in |
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* the array immediately following the end of the collection is set to |
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* {@code null}. |
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* |
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* <p>Like the {@link #toArray()} method, this method acts as bridge between |
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* array-based and collection-based APIs. Further, this method allows |
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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 {@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 {@code String}: |
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* |
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* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
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* |
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* Note that {@code toArray(new Object[0])} is identical in function to |
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* {@code toArray()}. |
440 |
* |
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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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* same runtime type is allocated for this purpose. |
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* @return an array containing all of the elements in this queue |
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* @throws ArrayStoreException if the runtime type of the specified array |
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* is not a supertype of the runtime type of every element in |
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* this queue |
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* @throws NullPointerException if the specified array is null |
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*/ |
450 |
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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if (a.length > size) |
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a[size] = null; |
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return a; |
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} |
460 |
|
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/** |
462 |
* Returns an iterator over the elements in this queue. The iterator |
463 |
* does not return the elements in any particular order. |
464 |
* |
465 |
* @return an iterator over the elements in this queue |
466 |
*/ |
467 |
public Iterator<E> iterator() { |
468 |
return new Itr(); |
469 |
} |
470 |
|
471 |
private final class Itr implements Iterator<E> { |
472 |
/** |
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* Index (into queue array) of element to be returned by |
474 |
* subsequent call to next. |
475 |
*/ |
476 |
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, |
480 |
* unless that element came from the forgetMeNot list. |
481 |
* Set to -1 if element is deleted by a call to remove. |
482 |
*/ |
483 |
private int lastRet = -1; |
484 |
|
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/** |
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* A queue of elements that were moved from the unvisited portion of |
487 |
* the heap into the visited portion as a result of "unlucky" element |
488 |
* removals during the iteration. (Unlucky element removals are those |
489 |
* that require a siftup instead of a siftdown.) We must visit all of |
490 |
* the elements in this list to complete the iteration. We do this |
491 |
* after we've completed the "normal" iteration. |
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* |
493 |
* We expect that most iterations, even those involving removals, |
494 |
* will not need to store elements in this field. |
495 |
*/ |
496 |
private ArrayDeque<E> forgetMeNot; |
497 |
|
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/** |
499 |
* Element returned by the most recent call to next iff that |
500 |
* element was drawn from the forgetMeNot list. |
501 |
*/ |
502 |
private E lastRetElt; |
503 |
|
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/** |
505 |
* The modCount value that the iterator believes that the backing |
506 |
* Queue should have. If this expectation is violated, the iterator |
507 |
* has detected concurrent modification. |
508 |
*/ |
509 |
private int expectedModCount = modCount; |
510 |
|
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Itr() {} // prevent access constructor creation |
512 |
|
513 |
public boolean hasNext() { |
514 |
return cursor < size || |
515 |
(forgetMeNot != null && !forgetMeNot.isEmpty()); |
516 |
} |
517 |
|
518 |
public E next() { |
519 |
if (expectedModCount != modCount) |
520 |
throw new ConcurrentModificationException(); |
521 |
if (cursor < size) |
522 |
return (E) queue[lastRet = cursor++]; |
523 |
if (forgetMeNot != null) { |
524 |
lastRet = -1; |
525 |
lastRetElt = forgetMeNot.poll(); |
526 |
if (lastRetElt != null) |
527 |
return lastRetElt; |
528 |
} |
529 |
throw new NoSuchElementException(); |
530 |
} |
531 |
|
532 |
public void remove() { |
533 |
if (expectedModCount != modCount) |
534 |
throw new ConcurrentModificationException(); |
535 |
if (lastRet != -1) { |
536 |
E moved = PriorityQueue.this.removeAt(lastRet); |
537 |
lastRet = -1; |
538 |
if (moved == null) |
539 |
cursor--; |
540 |
else { |
541 |
if (forgetMeNot == null) |
542 |
forgetMeNot = new ArrayDeque<>(); |
543 |
forgetMeNot.add(moved); |
544 |
} |
545 |
} else if (lastRetElt != null) { |
546 |
PriorityQueue.this.removeEq(lastRetElt); |
547 |
lastRetElt = null; |
548 |
} else { |
549 |
throw new IllegalStateException(); |
550 |
} |
551 |
expectedModCount = modCount; |
552 |
} |
553 |
} |
554 |
|
555 |
public int size() { |
556 |
return size; |
557 |
} |
558 |
|
559 |
/** |
560 |
* Removes all of the elements from this priority queue. |
561 |
* The queue will be empty after this call returns. |
562 |
*/ |
563 |
public void clear() { |
564 |
modCount++; |
565 |
final Object[] es = queue; |
566 |
for (int i = 0, n = size; i < n; i++) |
567 |
es[i] = null; |
568 |
size = 0; |
569 |
} |
570 |
|
571 |
public E poll() { |
572 |
final Object[] es; |
573 |
final E result; |
574 |
|
575 |
if ((result = (E) ((es = queue)[0])) != null) { |
576 |
modCount++; |
577 |
final int n; |
578 |
final E x = (E) es[(n = --size)]; |
579 |
es[n] = null; |
580 |
if (n > 0) { |
581 |
final Comparator<? super E> cmp; |
582 |
if ((cmp = comparator) == null) |
583 |
siftDownComparable(0, x, es, n); |
584 |
else |
585 |
siftDownUsingComparator(0, x, es, n, cmp); |
586 |
} |
587 |
} |
588 |
return result; |
589 |
} |
590 |
|
591 |
/** |
592 |
* Removes the ith element from queue. |
593 |
* |
594 |
* Normally this method leaves the elements at up to i-1, |
595 |
* inclusive, untouched. Under these circumstances, it returns |
596 |
* null. Occasionally, in order to maintain the heap invariant, |
597 |
* it must swap a later element of the list with one earlier than |
598 |
* i. Under these circumstances, this method returns the element |
599 |
* that was previously at the end of the list and is now at some |
600 |
* position before i. This fact is used by iterator.remove so as to |
601 |
* avoid missing traversing elements. |
602 |
*/ |
603 |
E removeAt(int i) { |
604 |
// assert i >= 0 && i < size; |
605 |
final Object[] es = queue; |
606 |
modCount++; |
607 |
int s = --size; |
608 |
if (s == i) // removed last element |
609 |
es[i] = null; |
610 |
else { |
611 |
E moved = (E) es[s]; |
612 |
es[s] = null; |
613 |
siftDown(i, moved); |
614 |
if (es[i] == moved) { |
615 |
siftUp(i, moved); |
616 |
if (es[i] != moved) |
617 |
return moved; |
618 |
} |
619 |
} |
620 |
return null; |
621 |
} |
622 |
|
623 |
/** |
624 |
* Inserts item x at position k, maintaining heap invariant by |
625 |
* promoting x up the tree until it is greater than or equal to |
626 |
* its parent, or is the root. |
627 |
* |
628 |
* To simplify and speed up coercions and comparisons, the |
629 |
* Comparable and Comparator versions are separated into different |
630 |
* methods that are otherwise identical. (Similarly for siftDown.) |
631 |
* |
632 |
* @param k the position to fill |
633 |
* @param x the item to insert |
634 |
*/ |
635 |
private void siftUp(int k, E x) { |
636 |
if (comparator != null) |
637 |
siftUpUsingComparator(k, x, queue, comparator); |
638 |
else |
639 |
siftUpComparable(k, x, queue); |
640 |
} |
641 |
|
642 |
private static <T> void siftUpComparable(int k, T x, Object[] es) { |
643 |
Comparable<? super T> key = (Comparable<? super T>) x; |
644 |
while (k > 0) { |
645 |
int parent = (k - 1) >>> 1; |
646 |
Object e = es[parent]; |
647 |
if (key.compareTo((T) e) >= 0) |
648 |
break; |
649 |
es[k] = e; |
650 |
k = parent; |
651 |
} |
652 |
es[k] = key; |
653 |
} |
654 |
|
655 |
private static <T> void siftUpUsingComparator( |
656 |
int k, T x, Object[] es, Comparator<? super T> cmp) { |
657 |
while (k > 0) { |
658 |
int parent = (k - 1) >>> 1; |
659 |
Object e = es[parent]; |
660 |
if (cmp.compare(x, (T) e) >= 0) |
661 |
break; |
662 |
es[k] = e; |
663 |
k = parent; |
664 |
} |
665 |
es[k] = x; |
666 |
} |
667 |
|
668 |
/** |
669 |
* Inserts item x at position k, maintaining heap invariant by |
670 |
* demoting x down the tree repeatedly until it is less than or |
671 |
* equal to its children or is a leaf. |
672 |
* |
673 |
* @param k the position to fill |
674 |
* @param x the item to insert |
675 |
*/ |
676 |
private void siftDown(int k, E x) { |
677 |
if (comparator != null) |
678 |
siftDownUsingComparator(k, x, queue, size, comparator); |
679 |
else |
680 |
siftDownComparable(k, x, queue, size); |
681 |
} |
682 |
|
683 |
private static <T> void siftDownComparable(int k, T x, Object[] es, int n) { |
684 |
// assert n > 0; |
685 |
Comparable<? super T> key = (Comparable<? super T>)x; |
686 |
int half = n >>> 1; // loop while a non-leaf |
687 |
while (k < half) { |
688 |
int child = (k << 1) + 1; // assume left child is least |
689 |
Object c = es[child]; |
690 |
int right = child + 1; |
691 |
if (right < n && |
692 |
((Comparable<? super T>) c).compareTo((T) es[right]) > 0) |
693 |
c = es[child = right]; |
694 |
if (key.compareTo((T) c) <= 0) |
695 |
break; |
696 |
es[k] = c; |
697 |
k = child; |
698 |
} |
699 |
es[k] = key; |
700 |
} |
701 |
|
702 |
private static <T> void siftDownUsingComparator( |
703 |
int k, T x, Object[] es, int n, Comparator<? super T> cmp) { |
704 |
// assert n > 0; |
705 |
int half = n >>> 1; |
706 |
while (k < half) { |
707 |
int child = (k << 1) + 1; |
708 |
Object c = es[child]; |
709 |
int right = child + 1; |
710 |
if (right < n && cmp.compare((T) c, (T) es[right]) > 0) |
711 |
c = es[child = right]; |
712 |
if (cmp.compare(x, (T) c) <= 0) |
713 |
break; |
714 |
es[k] = c; |
715 |
k = child; |
716 |
} |
717 |
es[k] = x; |
718 |
} |
719 |
|
720 |
/** |
721 |
* Establishes the heap invariant (described above) in the entire tree, |
722 |
* assuming nothing about the order of the elements prior to the call. |
723 |
* This classic algorithm due to Floyd (1964) is known to be O(size). |
724 |
*/ |
725 |
private void heapify() { |
726 |
final Object[] es = queue; |
727 |
int n = size, i = (n >>> 1) - 1; |
728 |
final Comparator<? super E> cmp; |
729 |
if ((cmp = comparator) == null) |
730 |
for (; i >= 0; i--) |
731 |
siftDownComparable(i, (E) es[i], es, n); |
732 |
else |
733 |
for (; i >= 0; i--) |
734 |
siftDownUsingComparator(i, (E) es[i], es, n, cmp); |
735 |
} |
736 |
|
737 |
/** |
738 |
* Returns the comparator used to order the elements in this |
739 |
* queue, or {@code null} if this queue is sorted according to |
740 |
* the {@linkplain Comparable natural ordering} of its elements. |
741 |
* |
742 |
* @return the comparator used to order this queue, or |
743 |
* {@code null} if this queue is sorted according to the |
744 |
* natural ordering of its elements |
745 |
*/ |
746 |
public Comparator<? super E> comparator() { |
747 |
return comparator; |
748 |
} |
749 |
|
750 |
/** |
751 |
* Saves this queue to a stream (that is, serializes it). |
752 |
* |
753 |
* @param s the stream |
754 |
* @throws java.io.IOException if an I/O error occurs |
755 |
* @serialData The length of the array backing the instance is |
756 |
* emitted (int), followed by all of its elements |
757 |
* (each an {@code Object}) in the proper order. |
758 |
*/ |
759 |
// OPENJDK @java.io.Serial |
760 |
private void writeObject(java.io.ObjectOutputStream s) |
761 |
throws java.io.IOException { |
762 |
// Write out element count, and any hidden stuff |
763 |
s.defaultWriteObject(); |
764 |
|
765 |
// Write out array length, for compatibility with 1.5 version |
766 |
s.writeInt(Math.max(2, size + 1)); |
767 |
|
768 |
// Write out all elements in the "proper order". |
769 |
final Object[] es = queue; |
770 |
for (int i = 0, n = size; i < n; i++) |
771 |
s.writeObject(es[i]); |
772 |
} |
773 |
|
774 |
/** |
775 |
* Reconstitutes the {@code PriorityQueue} instance from a stream |
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 |
// OPENJDK @java.io.Serial |
784 |
private void readObject(java.io.ObjectInputStream s) |
785 |
throws java.io.IOException, ClassNotFoundException { |
786 |
// Read in size, and any hidden stuff |
787 |
s.defaultReadObject(); |
788 |
|
789 |
// Read in (and discard) array length |
790 |
s.readInt(); |
791 |
|
792 |
jsr166.Platform.checkArray(s, Object[].class, size); |
793 |
final Object[] es = queue = new Object[Math.max(size, 1)]; |
794 |
|
795 |
// Read in all elements. |
796 |
for (int i = 0, n = size; i < n; i++) |
797 |
es[i] = s.readObject(); |
798 |
|
799 |
// Elements are guaranteed to be in "proper order", but the |
800 |
// spec has never explained what that might be. |
801 |
heapify(); |
802 |
} |
803 |
|
804 |
/** |
805 |
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em> |
806 |
* and <em>fail-fast</em> {@link Spliterator} over the elements in this |
807 |
* queue. The spliterator does not traverse elements in any particular order |
808 |
* (the {@link Spliterator#ORDERED ORDERED} characteristic is not reported). |
809 |
* |
810 |
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED}, |
811 |
* {@link Spliterator#SUBSIZED}, and {@link Spliterator#NONNULL}. |
812 |
* Overriding implementations should document the reporting of additional |
813 |
* characteristic values. |
814 |
* |
815 |
* @return a {@code Spliterator} over the elements in this queue |
816 |
* @since 1.8 |
817 |
*/ |
818 |
public final Spliterator<E> spliterator() { |
819 |
return new PriorityQueueSpliterator(0, -1, 0); |
820 |
} |
821 |
|
822 |
final class PriorityQueueSpliterator implements Spliterator<E> { |
823 |
private int index; // current index, modified on advance/split |
824 |
private int fence; // -1 until first use |
825 |
private int expectedModCount; // initialized when fence set |
826 |
|
827 |
/** Creates new spliterator covering the given range. */ |
828 |
PriorityQueueSpliterator(int origin, int fence, int expectedModCount) { |
829 |
this.index = origin; |
830 |
this.fence = fence; |
831 |
this.expectedModCount = expectedModCount; |
832 |
} |
833 |
|
834 |
private int getFence() { // initialize fence to size on first use |
835 |
int hi; |
836 |
if ((hi = fence) < 0) { |
837 |
expectedModCount = modCount; |
838 |
hi = fence = size; |
839 |
} |
840 |
return hi; |
841 |
} |
842 |
|
843 |
public PriorityQueueSpliterator trySplit() { |
844 |
int hi = getFence(), lo = index, mid = (lo + hi) >>> 1; |
845 |
return (lo >= mid) ? null : |
846 |
new PriorityQueueSpliterator(lo, index = mid, expectedModCount); |
847 |
} |
848 |
|
849 |
public void forEachRemaining(Consumer<? super E> action) { |
850 |
if (action == null) |
851 |
throw new NullPointerException(); |
852 |
if (fence < 0) { fence = size; expectedModCount = modCount; } |
853 |
final Object[] es = queue; |
854 |
int i, hi; E e; |
855 |
for (i = index, index = hi = fence; i < hi; i++) { |
856 |
if ((e = (E) es[i]) == null) |
857 |
break; // must be CME |
858 |
action.accept(e); |
859 |
} |
860 |
if (modCount != expectedModCount) |
861 |
throw new ConcurrentModificationException(); |
862 |
} |
863 |
|
864 |
public boolean tryAdvance(Consumer<? super E> action) { |
865 |
if (action == null) |
866 |
throw new NullPointerException(); |
867 |
if (fence < 0) { fence = size; expectedModCount = modCount; } |
868 |
int i; |
869 |
if ((i = index) < fence) { |
870 |
index = i + 1; |
871 |
E e; |
872 |
if ((e = (E) queue[i]) == null |
873 |
|| modCount != expectedModCount) |
874 |
throw new ConcurrentModificationException(); |
875 |
action.accept(e); |
876 |
return true; |
877 |
} |
878 |
return false; |
879 |
} |
880 |
|
881 |
public long estimateSize() { |
882 |
return getFence() - index; |
883 |
} |
884 |
|
885 |
public int characteristics() { |
886 |
return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL; |
887 |
} |
888 |
} |
889 |
|
890 |
/** |
891 |
* @throws NullPointerException {@inheritDoc} |
892 |
*/ |
893 |
public boolean removeIf(Predicate<? super E> filter) { |
894 |
Objects.requireNonNull(filter); |
895 |
return bulkRemove(filter); |
896 |
} |
897 |
|
898 |
/** |
899 |
* @throws NullPointerException {@inheritDoc} |
900 |
*/ |
901 |
public boolean removeAll(Collection<?> c) { |
902 |
Objects.requireNonNull(c); |
903 |
return bulkRemove(e -> c.contains(e)); |
904 |
} |
905 |
|
906 |
/** |
907 |
* @throws NullPointerException {@inheritDoc} |
908 |
*/ |
909 |
public boolean retainAll(Collection<?> c) { |
910 |
Objects.requireNonNull(c); |
911 |
return bulkRemove(e -> !c.contains(e)); |
912 |
} |
913 |
|
914 |
// A tiny bit set implementation |
915 |
|
916 |
private static long[] nBits(int n) { |
917 |
return new long[((n - 1) >> 6) + 1]; |
918 |
} |
919 |
private static void setBit(long[] bits, int i) { |
920 |
bits[i >> 6] |= 1L << i; |
921 |
} |
922 |
private static boolean isClear(long[] bits, int i) { |
923 |
return (bits[i >> 6] & (1L << i)) == 0; |
924 |
} |
925 |
|
926 |
/** Implementation of bulk remove methods. */ |
927 |
private boolean bulkRemove(Predicate<? super E> filter) { |
928 |
final int expectedModCount = ++modCount; |
929 |
final Object[] es = queue; |
930 |
final int end = size; |
931 |
int i; |
932 |
// Optimize for initial run of survivors |
933 |
for (i = 0; i < end && !filter.test((E) es[i]); i++) |
934 |
; |
935 |
if (i >= end) { |
936 |
if (modCount != expectedModCount) |
937 |
throw new ConcurrentModificationException(); |
938 |
return false; |
939 |
} |
940 |
// Tolerate predicates that reentrantly access the collection for |
941 |
// read (but writers still get CME), so traverse once to find |
942 |
// elements to delete, a second pass to physically expunge. |
943 |
final int beg = i; |
944 |
final long[] deathRow = nBits(end - beg); |
945 |
deathRow[0] = 1L; // set bit 0 |
946 |
for (i = beg + 1; i < end; i++) |
947 |
if (filter.test((E) es[i])) |
948 |
setBit(deathRow, i - beg); |
949 |
if (modCount != expectedModCount) |
950 |
throw new ConcurrentModificationException(); |
951 |
int w = beg; |
952 |
for (i = beg; i < end; i++) |
953 |
if (isClear(deathRow, i - beg)) |
954 |
es[w++] = es[i]; |
955 |
for (i = size = w; i < end; i++) |
956 |
es[i] = null; |
957 |
heapify(); |
958 |
return true; |
959 |
} |
960 |
|
961 |
/** |
962 |
* @throws NullPointerException {@inheritDoc} |
963 |
*/ |
964 |
public void forEach(Consumer<? super E> action) { |
965 |
Objects.requireNonNull(action); |
966 |
final int expectedModCount = modCount; |
967 |
final Object[] es = queue; |
968 |
for (int i = 0, n = size; i < n; i++) |
969 |
action.accept((E) es[i]); |
970 |
if (expectedModCount != modCount) |
971 |
throw new ConcurrentModificationException(); |
972 |
} |
973 |
} |