1006 lines
36 KiB
Java
1006 lines
36 KiB
Java
/*
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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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package java.util;
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import android.compat.Compatibility;
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import android.compat.annotation.ChangeId;
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import android.compat.annotation.EnabledSince;
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import dalvik.annotation.compat.VersionCodes;
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import dalvik.system.VMRuntime;
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import java.util.function.Consumer;
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import java.util.function.Predicate;
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import jdk.internal.access.SharedSecrets;
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import jdk.internal.util.ArraysSupport;
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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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@java.io.Serial
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private static final long serialVersionUID = -7720805057305804111L;
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private static final int DEFAULT_INITIAL_CAPACITY = 11;
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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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* 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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* The comparator, or null if priority queue uses elements'
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* natural ordering.
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*/
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@SuppressWarnings("serial") // Conditionally serializable
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private final Comparator<? super E> comparator;
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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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* 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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* 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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* 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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* 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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* 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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* 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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* 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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/** 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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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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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.getClass() != ArrayList.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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* 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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* 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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* 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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* 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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if (i == 0) {
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// Android-changed: Keep old behavior on Android 13 or below. http://b/289878283
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boolean usePreAndroidUBehavior = VMRuntime.getSdkVersion() < VersionCodes.UPSIDE_DOWN_CAKE
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|| !Compatibility.isChangeEnabled(PRIORITY_QUEUE_OFFER_NON_COMPARABLE_ONE_ELEMENT);
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if (usePreAndroidUBehavior) {
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queue[0] = e;
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} else {
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siftUp(i, e);
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}
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} else {
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siftUp(i, e);
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}
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size = i + 1;
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return true;
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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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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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* 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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* 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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* 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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* 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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* 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()}.
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*
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* @param a the array into which the elements of the queue are to
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* be stored, if it is big enough; otherwise, a new array of the
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* 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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*/
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public <T> T[] toArray(T[] a) {
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final int size = this.size;
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if (a.length < size)
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// Make a new array of a's runtime type, but my contents:
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return (T[]) Arrays.copyOf(queue, size, a.getClass());
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System.arraycopy(queue, 0, a, 0, size);
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if (a.length > size)
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a[size] = null;
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return a;
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}
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/**
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* Returns an iterator over the elements in this queue. The iterator
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* does not return the elements in any particular order.
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*
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* @return an iterator over the elements in this queue
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*/
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public Iterator<E> iterator() {
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return new Itr();
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}
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private final class Itr implements Iterator<E> {
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/**
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* Index (into queue array) of element to be returned by
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* subsequent call to next.
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*/
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private int cursor;
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/**
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* Index of element returned by most recent call to next,
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* unless that element came from the forgetMeNot list.
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* Set to -1 if element is deleted by a call to remove.
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*/
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private int lastRet = -1;
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/**
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* A queue of elements that were moved from the unvisited portion of
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* the heap into the visited portion as a result of "unlucky" element
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* removals during the iteration. (Unlucky element removals are those
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|
* that require a siftup instead of a siftdown.) We must visit all of
|
|
* the elements in this list to complete the iteration. We do this
|
|
* after we've completed the "normal" iteration.
|
|
*
|
|
* We expect that most iterations, even those involving removals,
|
|
* will not need to store elements in this field.
|
|
*/
|
|
private ArrayDeque<E> forgetMeNot;
|
|
|
|
/**
|
|
* Element returned by the most recent call to next iff that
|
|
* element was drawn from the forgetMeNot list.
|
|
*/
|
|
private E lastRetElt;
|
|
|
|
/**
|
|
* The modCount value that the iterator believes that the backing
|
|
* Queue should have. If this expectation is violated, the iterator
|
|
* has detected concurrent modification.
|
|
*/
|
|
private int expectedModCount = modCount;
|
|
|
|
Itr() {} // prevent access constructor creation
|
|
|
|
public boolean hasNext() {
|
|
return cursor < size ||
|
|
(forgetMeNot != null && !forgetMeNot.isEmpty());
|
|
}
|
|
|
|
public E next() {
|
|
if (expectedModCount != modCount)
|
|
throw new ConcurrentModificationException();
|
|
if (cursor < size)
|
|
return (E) queue[lastRet = cursor++];
|
|
if (forgetMeNot != null) {
|
|
lastRet = -1;
|
|
lastRetElt = forgetMeNot.poll();
|
|
if (lastRetElt != null)
|
|
return lastRetElt;
|
|
}
|
|
throw new NoSuchElementException();
|
|
}
|
|
|
|
public void remove() {
|
|
if (expectedModCount != modCount)
|
|
throw new ConcurrentModificationException();
|
|
if (lastRet != -1) {
|
|
E moved = PriorityQueue.this.removeAt(lastRet);
|
|
lastRet = -1;
|
|
if (moved == null)
|
|
cursor--;
|
|
else {
|
|
if (forgetMeNot == null)
|
|
forgetMeNot = new ArrayDeque<>();
|
|
forgetMeNot.add(moved);
|
|
}
|
|
} else if (lastRetElt != null) {
|
|
PriorityQueue.this.removeEq(lastRetElt);
|
|
lastRetElt = null;
|
|
} else {
|
|
throw new IllegalStateException();
|
|
}
|
|
expectedModCount = modCount;
|
|
}
|
|
}
|
|
|
|
public int size() {
|
|
return size;
|
|
}
|
|
|
|
/**
|
|
* Removes all of the elements from this priority queue.
|
|
* The queue will be empty after this call returns.
|
|
*/
|
|
public void clear() {
|
|
modCount++;
|
|
final Object[] es = queue;
|
|
for (int i = 0, n = size; i < n; i++)
|
|
es[i] = null;
|
|
size = 0;
|
|
}
|
|
|
|
public E poll() {
|
|
final Object[] es;
|
|
final E result;
|
|
|
|
if ((result = (E) ((es = queue)[0])) != null) {
|
|
modCount++;
|
|
final int n;
|
|
final E x = (E) es[(n = --size)];
|
|
es[n] = null;
|
|
if (n > 0) {
|
|
final Comparator<? super E> cmp;
|
|
if ((cmp = comparator) == null)
|
|
siftDownComparable(0, x, es, n);
|
|
else
|
|
siftDownUsingComparator(0, x, es, n, cmp);
|
|
}
|
|
}
|
|
return result;
|
|
}
|
|
|
|
/**
|
|
* Removes the ith element from queue.
|
|
*
|
|
* Normally this method leaves the elements at up to i-1,
|
|
* inclusive, untouched. Under these circumstances, it returns
|
|
* null. Occasionally, in order to maintain the heap invariant,
|
|
* it must swap a later element of the list with one earlier than
|
|
* i. Under these circumstances, this method returns the element
|
|
* that was previously at the end of the list and is now at some
|
|
* position before i. This fact is used by iterator.remove so as to
|
|
* avoid missing traversing elements.
|
|
*/
|
|
E removeAt(int i) {
|
|
// assert i >= 0 && i < size;
|
|
final Object[] es = queue;
|
|
modCount++;
|
|
int s = --size;
|
|
if (s == i) // removed last element
|
|
es[i] = null;
|
|
else {
|
|
E moved = (E) es[s];
|
|
es[s] = null;
|
|
siftDown(i, moved);
|
|
if (es[i] == moved) {
|
|
siftUp(i, moved);
|
|
if (es[i] != moved)
|
|
return moved;
|
|
}
|
|
}
|
|
return null;
|
|
}
|
|
|
|
/**
|
|
* Inserts item x at position k, maintaining heap invariant by
|
|
* promoting x up the tree until it is greater than or equal to
|
|
* its parent, or is the root.
|
|
*
|
|
* To simplify and speed up coercions and comparisons, the
|
|
* Comparable and Comparator versions are separated into different
|
|
* methods that are otherwise identical. (Similarly for siftDown.)
|
|
*
|
|
* @param k the position to fill
|
|
* @param x the item to insert
|
|
*/
|
|
private void siftUp(int k, E x) {
|
|
if (comparator != null)
|
|
siftUpUsingComparator(k, x, queue, comparator);
|
|
else
|
|
siftUpComparable(k, x, queue);
|
|
}
|
|
|
|
private static <T> void siftUpComparable(int k, T x, Object[] es) {
|
|
Comparable<? super T> key = (Comparable<? super T>) x;
|
|
while (k > 0) {
|
|
int parent = (k - 1) >>> 1;
|
|
Object e = es[parent];
|
|
if (key.compareTo((T) e) >= 0)
|
|
break;
|
|
es[k] = e;
|
|
k = parent;
|
|
}
|
|
es[k] = key;
|
|
}
|
|
|
|
private static <T> void siftUpUsingComparator(
|
|
int k, T x, Object[] es, Comparator<? super T> cmp) {
|
|
while (k > 0) {
|
|
int parent = (k - 1) >>> 1;
|
|
Object e = es[parent];
|
|
if (cmp.compare(x, (T) e) >= 0)
|
|
break;
|
|
es[k] = e;
|
|
k = parent;
|
|
}
|
|
es[k] = x;
|
|
}
|
|
|
|
/**
|
|
* Inserts item x at position k, maintaining heap invariant by
|
|
* demoting x down the tree repeatedly until it is less than or
|
|
* equal to its children or is a leaf.
|
|
*
|
|
* @param k the position to fill
|
|
* @param x the item to insert
|
|
*/
|
|
private void siftDown(int k, E x) {
|
|
if (comparator != null)
|
|
siftDownUsingComparator(k, x, queue, size, comparator);
|
|
else
|
|
siftDownComparable(k, x, queue, size);
|
|
}
|
|
|
|
private static <T> void siftDownComparable(int k, T x, Object[] es, int n) {
|
|
// assert n > 0;
|
|
Comparable<? super T> key = (Comparable<? super T>)x;
|
|
int half = n >>> 1; // loop while a non-leaf
|
|
while (k < half) {
|
|
int child = (k << 1) + 1; // assume left child is least
|
|
Object c = es[child];
|
|
int right = child + 1;
|
|
if (right < n &&
|
|
((Comparable<? super T>) c).compareTo((T) es[right]) > 0)
|
|
c = es[child = right];
|
|
if (key.compareTo((T) c) <= 0)
|
|
break;
|
|
es[k] = c;
|
|
k = child;
|
|
}
|
|
es[k] = key;
|
|
}
|
|
|
|
private static <T> void siftDownUsingComparator(
|
|
int k, T x, Object[] es, int n, Comparator<? super T> cmp) {
|
|
// assert n > 0;
|
|
int half = n >>> 1;
|
|
while (k < half) {
|
|
int child = (k << 1) + 1;
|
|
Object c = es[child];
|
|
int right = child + 1;
|
|
if (right < n && cmp.compare((T) c, (T) es[right]) > 0)
|
|
c = es[child = right];
|
|
if (cmp.compare(x, (T) c) <= 0)
|
|
break;
|
|
es[k] = c;
|
|
k = child;
|
|
}
|
|
es[k] = x;
|
|
}
|
|
|
|
/**
|
|
* Establishes the heap invariant (described above) in the entire tree,
|
|
* assuming nothing about the order of the elements prior to the call.
|
|
* This classic algorithm due to Floyd (1964) is known to be O(size).
|
|
*/
|
|
private void heapify() {
|
|
final Object[] es = queue;
|
|
int n = size, i = (n >>> 1) - 1;
|
|
final Comparator<? super E> cmp;
|
|
if ((cmp = comparator) == null)
|
|
for (; i >= 0; i--)
|
|
siftDownComparable(i, (E) es[i], es, n);
|
|
else
|
|
for (; i >= 0; i--)
|
|
siftDownUsingComparator(i, (E) es[i], es, n, cmp);
|
|
}
|
|
|
|
/**
|
|
* Returns the comparator used to order the elements in this
|
|
* queue, or {@code null} if this queue is sorted according to
|
|
* the {@linkplain Comparable natural ordering} of its elements.
|
|
*
|
|
* @return the comparator used to order this queue, or
|
|
* {@code null} if this queue is sorted according to the
|
|
* natural ordering of its elements
|
|
*/
|
|
public Comparator<? super E> comparator() {
|
|
return comparator;
|
|
}
|
|
|
|
/**
|
|
* Saves this queue to a stream (that is, serializes it).
|
|
*
|
|
* @param s the stream
|
|
* @throws java.io.IOException if an I/O error occurs
|
|
* @serialData The length of the array backing the instance is
|
|
* emitted (int), followed by all of its elements
|
|
* (each an {@code Object}) in the proper order.
|
|
*/
|
|
@java.io.Serial
|
|
private void writeObject(java.io.ObjectOutputStream s)
|
|
throws java.io.IOException {
|
|
// Write out element count, and any hidden stuff
|
|
s.defaultWriteObject();
|
|
|
|
// Write out array length, for compatibility with 1.5 version
|
|
s.writeInt(Math.max(2, size + 1));
|
|
|
|
// Write out all elements in the "proper order".
|
|
final Object[] es = queue;
|
|
for (int i = 0, n = size; i < n; i++)
|
|
s.writeObject(es[i]);
|
|
}
|
|
|
|
/**
|
|
* Reconstitutes the {@code PriorityQueue} instance from a stream
|
|
* (that is, deserializes it).
|
|
*
|
|
* @param s the stream
|
|
* @throws ClassNotFoundException if the class of a serialized object
|
|
* could not be found
|
|
* @throws java.io.IOException if an I/O error occurs
|
|
*/
|
|
@java.io.Serial
|
|
private void readObject(java.io.ObjectInputStream s)
|
|
throws java.io.IOException, ClassNotFoundException {
|
|
// Read in size, and any hidden stuff
|
|
s.defaultReadObject();
|
|
|
|
// Read in (and discard) array length
|
|
s.readInt();
|
|
|
|
SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, size);
|
|
final Object[] es = queue = new Object[Math.max(size, 1)];
|
|
|
|
// Read in all elements.
|
|
for (int i = 0, n = size; i < n; i++)
|
|
es[i] = s.readObject();
|
|
|
|
// Elements are guaranteed to be in "proper order", but the
|
|
// spec has never explained what that might be.
|
|
heapify();
|
|
}
|
|
|
|
/**
|
|
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
|
|
* and <em>fail-fast</em> {@link Spliterator} over the elements in this
|
|
* queue. The spliterator does not traverse elements in any particular order
|
|
* (the {@link Spliterator#ORDERED ORDERED} characteristic is not reported).
|
|
*
|
|
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
|
|
* {@link Spliterator#SUBSIZED}, and {@link Spliterator#NONNULL}.
|
|
* Overriding implementations should document the reporting of additional
|
|
* characteristic values.
|
|
*
|
|
* @return a {@code Spliterator} over the elements in this queue
|
|
* @since 1.8
|
|
*/
|
|
public final Spliterator<E> spliterator() {
|
|
return new PriorityQueueSpliterator(0, -1, 0);
|
|
}
|
|
|
|
final class PriorityQueueSpliterator implements Spliterator<E> {
|
|
private int index; // current index, modified on advance/split
|
|
private int fence; // -1 until first use
|
|
private int expectedModCount; // initialized when fence set
|
|
|
|
/** Creates new spliterator covering the given range. */
|
|
PriorityQueueSpliterator(int origin, int fence, int expectedModCount) {
|
|
this.index = origin;
|
|
this.fence = fence;
|
|
this.expectedModCount = expectedModCount;
|
|
}
|
|
|
|
private int getFence() { // initialize fence to size on first use
|
|
int hi;
|
|
if ((hi = fence) < 0) {
|
|
expectedModCount = modCount;
|
|
hi = fence = size;
|
|
}
|
|
return hi;
|
|
}
|
|
|
|
public PriorityQueueSpliterator trySplit() {
|
|
int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
|
|
return (lo >= mid) ? null :
|
|
new PriorityQueueSpliterator(lo, index = mid, expectedModCount);
|
|
}
|
|
|
|
public void forEachRemaining(Consumer<? super E> action) {
|
|
if (action == null)
|
|
throw new NullPointerException();
|
|
if (fence < 0) { fence = size; expectedModCount = modCount; }
|
|
final Object[] es = queue;
|
|
int i, hi; E e;
|
|
for (i = index, index = hi = fence; i < hi; i++) {
|
|
if ((e = (E) es[i]) == null)
|
|
break; // must be CME
|
|
action.accept(e);
|
|
}
|
|
if (modCount != expectedModCount)
|
|
throw new ConcurrentModificationException();
|
|
}
|
|
|
|
public boolean tryAdvance(Consumer<? super E> action) {
|
|
if (action == null)
|
|
throw new NullPointerException();
|
|
if (fence < 0) { fence = size; expectedModCount = modCount; }
|
|
int i;
|
|
if ((i = index) < fence) {
|
|
index = i + 1;
|
|
E e;
|
|
if ((e = (E) queue[i]) == null
|
|
|| modCount != expectedModCount)
|
|
throw new ConcurrentModificationException();
|
|
action.accept(e);
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
public long estimateSize() {
|
|
return getFence() - index;
|
|
}
|
|
|
|
public int characteristics() {
|
|
return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* @throws NullPointerException {@inheritDoc}
|
|
*/
|
|
public boolean removeIf(Predicate<? super E> filter) {
|
|
Objects.requireNonNull(filter);
|
|
return bulkRemove(filter);
|
|
}
|
|
|
|
/**
|
|
* @throws NullPointerException {@inheritDoc}
|
|
*/
|
|
public boolean removeAll(Collection<?> c) {
|
|
Objects.requireNonNull(c);
|
|
return bulkRemove(e -> c.contains(e));
|
|
}
|
|
|
|
/**
|
|
* @throws NullPointerException {@inheritDoc}
|
|
*/
|
|
public boolean retainAll(Collection<?> c) {
|
|
Objects.requireNonNull(c);
|
|
return bulkRemove(e -> !c.contains(e));
|
|
}
|
|
|
|
// A tiny bit set implementation
|
|
|
|
private static long[] nBits(int n) {
|
|
return new long[((n - 1) >> 6) + 1];
|
|
}
|
|
private static void setBit(long[] bits, int i) {
|
|
bits[i >> 6] |= 1L << i;
|
|
}
|
|
private static boolean isClear(long[] bits, int i) {
|
|
return (bits[i >> 6] & (1L << i)) == 0;
|
|
}
|
|
|
|
/** Implementation of bulk remove methods. */
|
|
private boolean bulkRemove(Predicate<? super E> filter) {
|
|
final int expectedModCount = ++modCount;
|
|
final Object[] es = queue;
|
|
final int end = size;
|
|
int i;
|
|
// Optimize for initial run of survivors
|
|
for (i = 0; i < end && !filter.test((E) es[i]); i++)
|
|
;
|
|
if (i >= end) {
|
|
if (modCount != expectedModCount)
|
|
throw new ConcurrentModificationException();
|
|
return false;
|
|
}
|
|
// Tolerate predicates that reentrantly access the collection for
|
|
// read (but writers still get CME), so traverse once to find
|
|
// elements to delete, a second pass to physically expunge.
|
|
final int beg = i;
|
|
final long[] deathRow = nBits(end - beg);
|
|
deathRow[0] = 1L; // set bit 0
|
|
for (i = beg + 1; i < end; i++)
|
|
if (filter.test((E) es[i]))
|
|
setBit(deathRow, i - beg);
|
|
if (modCount != expectedModCount)
|
|
throw new ConcurrentModificationException();
|
|
int w = beg;
|
|
for (i = beg; i < end; i++)
|
|
if (isClear(deathRow, i - beg))
|
|
es[w++] = es[i];
|
|
for (i = size = w; i < end; i++)
|
|
es[i] = null;
|
|
heapify();
|
|
return true;
|
|
}
|
|
|
|
/**
|
|
* @throws NullPointerException {@inheritDoc}
|
|
*/
|
|
public void forEach(Consumer<? super E> action) {
|
|
Objects.requireNonNull(action);
|
|
final int expectedModCount = modCount;
|
|
final Object[] es = queue;
|
|
for (int i = 0, n = size; i < n; i++)
|
|
action.accept((E) es[i]);
|
|
if (expectedModCount != modCount)
|
|
throw new ConcurrentModificationException();
|
|
}
|
|
|
|
// Android-added: Backward-compatible flag for offer() API.
|
|
/**
|
|
* Since Android 14, {@link PriorityQueue#offer(E)} requires all elements to be comparable if
|
|
* there was no comparator. Previously, the first element being added did not need to be
|
|
* comparable.
|
|
*
|
|
* This flag is enabled for apps targeting Android 14+.
|
|
*
|
|
* @hide
|
|
*/
|
|
@ChangeId
|
|
@EnabledSince(targetSdkVersion = VersionCodes.UPSIDE_DOWN_CAKE)
|
|
public static final long PRIORITY_QUEUE_OFFER_NON_COMPARABLE_ONE_ELEMENT = 289878283L;
|
|
}
|