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/* |
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* %W% %E% |
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* Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* Copyright 2006 Sun Microsystems, Inc. All rights reserved. |
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* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. Oracle designates this |
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* particular file as subject to the "Classpath" exception as provided |
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* by Oracle in the LICENSE file that accompanied this code. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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*/ |
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|
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package java.util; |
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|
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import java.util.function.Consumer; |
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|
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/** |
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* An unbounded priority {@linkplain Queue queue} based on a priority heap. |
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* The elements of the priority queue are ordered according to their |
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* the priority queue in any particular order. If you need ordered |
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* traversal, consider using {@code Arrays.sort(pq.toArray())}. |
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* |
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* <p> <strong>Note that this implementation is not synchronized.</strong> |
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* <p><strong>Note that this implementation is not synchronized.</strong> |
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* Multiple threads should not access a {@code PriorityQueue} |
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* instance concurrently if any of the threads modifies the queue. |
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* Instead, use the thread-safe {@link |
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* java.util.concurrent.PriorityBlockingQueue} class. |
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* |
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* <p>Implementation note: this implementation provides |
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* O(log(n)) time for the enqueing and dequeing methods |
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* O(log(n)) time for the enqueuing and dequeuing methods |
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* ({@code offer}, {@code poll}, {@code remove()} and {@code add}); |
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* linear time for the {@code remove(Object)} and {@code contains(Object)} |
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* methods; and constant time for the retrieval methods |
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* Java Collections Framework</a>. |
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* |
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* @since 1.5 |
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– |
* @version %I%, %G% |
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* @author Josh Bloch, Doug Lea |
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* @param <E> the type of elements held in this collection |
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* @param <E> the type of elements held in this queue |
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*/ |
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public class PriorityQueue<E> extends AbstractQueue<E> |
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implements java.io.Serializable { |
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* heap and each descendant d of n, n <= d. The element with the |
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* lowest value is in queue[0], assuming the queue is nonempty. |
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*/ |
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private transient Object[] queue; |
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transient Object[] queue; // non-private to simplify nested class access |
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|
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/** |
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* The number of elements in the priority queue. |
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*/ |
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private int size = 0; |
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private int size; |
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|
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/** |
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* The comparator, or null if priority queue uses elements' |
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* The number of times this priority queue has been |
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* <i>structurally modified</i>. See AbstractList for gory details. |
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*/ |
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private transient int modCount = 0; |
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transient int modCount; // non-private for 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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* @throws NullPointerException if the specified collection or any |
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* of its elements are null |
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*/ |
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@SuppressWarnings("unchecked") |
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public PriorityQueue(Collection<? extends E> c) { |
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initFromCollection(c); |
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if (c instanceof SortedSet) |
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comparator = (Comparator<? super E>) |
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((SortedSet<? extends E>)c).comparator(); |
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else if (c instanceof PriorityQueue) |
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comparator = (Comparator<? super E>) |
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((PriorityQueue<? extends E>)c).comparator(); |
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if (c instanceof SortedSet<?>) { |
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SortedSet<? extends E> ss = (SortedSet<? extends E>) c; |
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this.comparator = (Comparator<? super E>) ss.comparator(); |
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initElementsFromCollection(ss); |
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} |
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else if (c instanceof PriorityQueue<?>) { |
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PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c; |
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this.comparator = (Comparator<? super E>) pq.comparator(); |
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initFromPriorityQueue(pq); |
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} |
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else { |
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comparator = null; |
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heapify(); |
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this.comparator = null; |
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initFromCollection(c); |
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} |
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} |
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|
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* @throws NullPointerException if the specified priority queue or any |
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* of its elements are null |
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*/ |
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@SuppressWarnings("unchecked") |
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public PriorityQueue(PriorityQueue<? extends E> c) { |
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comparator = (Comparator<? super E>)c.comparator(); |
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initFromCollection(c); |
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this.comparator = (Comparator<? super E>) c.comparator(); |
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initFromPriorityQueue(c); |
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} |
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|
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/** |
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* @throws NullPointerException if the specified sorted set or any |
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* of its elements are null |
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*/ |
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@SuppressWarnings("unchecked") |
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public PriorityQueue(SortedSet<? extends E> c) { |
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comparator = (Comparator<? super E>)c.comparator(); |
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initFromCollection(c); |
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this.comparator = (Comparator<? super E>) c.comparator(); |
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initElementsFromCollection(c); |
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} |
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|
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private void initFromPriorityQueue(PriorityQueue<? extends E> c) { |
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> |
if (c.getClass() == PriorityQueue.class) { |
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this.queue = c.toArray(); |
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> |
this.size = c.size(); |
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} else { |
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initFromCollection(c); |
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} |
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} |
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|
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private void initElementsFromCollection(Collection<? extends E> c) { |
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Object[] a = c.toArray(); |
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// If c.toArray incorrectly doesn't return Object[], copy it. |
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if (a.getClass() != Object[].class) |
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a = Arrays.copyOf(a, a.length, Object[].class); |
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> |
int len = a.length; |
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> |
if (len == 1 || this.comparator != null) |
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> |
for (int i = 0; i < len; i++) |
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> |
if (a[i] == null) |
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throw new NullPointerException(); |
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> |
this.queue = a; |
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> |
this.size = a.length; |
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} |
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|
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/** |
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* @param c the collection |
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*/ |
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private void initFromCollection(Collection<? extends E> c) { |
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Object[] a = c.toArray(); |
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< |
// If c.toArray incorrectly doesn't return Object[], copy it. |
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if (a.getClass() != Object[].class) |
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< |
a = Arrays.copyOf(a, a.length, Object[].class); |
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queue = a; |
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size = a.length; |
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> |
initElementsFromCollection(c); |
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> |
heapify(); |
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} |
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|
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/** |
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* The maximum size of array to allocate. |
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* Some VMs reserve some header words in an array. |
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* Attempts to allocate larger arrays may result in |
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* OutOfMemoryError: Requested array size exceeds VM limit |
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*/ |
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+ |
private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; |
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+ |
|
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+ |
/** |
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* Increases the capacity of the array. |
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* |
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* @param minCapacity the desired minimum capacity |
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*/ |
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private void grow(int minCapacity) { |
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< |
if (minCapacity < 0) // overflow |
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throw new OutOfMemoryError(); |
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< |
int oldCapacity = queue.length; |
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> |
int oldCapacity = queue.length; |
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// Double size if small; else grow by 50% |
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< |
int newCapacity = ((oldCapacity < 64)? |
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< |
((oldCapacity + 1) * 2): |
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< |
((oldCapacity / 2) * 3)); |
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< |
if (newCapacity < 0) // overflow |
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< |
newCapacity = Integer.MAX_VALUE; |
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< |
if (newCapacity < minCapacity) |
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newCapacity = minCapacity; |
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> |
int newCapacity = oldCapacity + ((oldCapacity < 64) ? |
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> |
(oldCapacity + 2) : |
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> |
(oldCapacity >> 1)); |
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> |
// overflow-conscious code |
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> |
if (newCapacity - MAX_ARRAY_SIZE > 0) |
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> |
newCapacity = hugeCapacity(minCapacity); |
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queue = Arrays.copyOf(queue, newCapacity); |
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} |
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|
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+ |
private static int hugeCapacity(int minCapacity) { |
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if (minCapacity < 0) // overflow |
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+ |
throw new OutOfMemoryError(); |
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+ |
return (minCapacity > MAX_ARRAY_SIZE) ? |
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Integer.MAX_VALUE : |
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+ |
MAX_ARRAY_SIZE; |
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} |
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|
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/** |
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* Inserts the specified element into this priority queue. |
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* |
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return true; |
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} |
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|
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+ |
@SuppressWarnings("unchecked") |
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public E peek() { |
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< |
if (size == 0) |
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< |
return null; |
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< |
return (E) queue[0]; |
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> |
return (size == 0) ? null : (E) queue[0]; |
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} |
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|
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private int indexOf(Object o) { |
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< |
if (o != null) { |
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> |
if (o != null) { |
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for (int i = 0; i < size; i++) |
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if (o.equals(queue[i])) |
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return i; |
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* @return {@code true} if this queue changed as a result of the call |
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*/ |
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public boolean remove(Object o) { |
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< |
int i = indexOf(o); |
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< |
if (i == -1) |
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< |
return false; |
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< |
else { |
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< |
removeAt(i); |
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< |
return true; |
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< |
} |
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> |
int i = indexOf(o); |
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> |
if (i == -1) |
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> |
return false; |
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> |
else { |
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> |
removeAt(i); |
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> |
return true; |
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> |
} |
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} |
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|
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/** |
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* @return {@code true} if removed |
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*/ |
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boolean removeEq(Object o) { |
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< |
for (int i = 0; i < size; i++) { |
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< |
if (o == queue[i]) { |
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> |
for (int i = 0; i < size; i++) { |
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> |
if (o == queue[i]) { |
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removeAt(i); |
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return true; |
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} |
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* @return {@code true} if this queue contains the specified element |
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*/ |
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public boolean contains(Object o) { |
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< |
return indexOf(o) != -1; |
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> |
return indexOf(o) >= 0; |
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} |
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|
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/** |
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* precise control over the runtime type of the output array, and may, |
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* under certain circumstances, be used to save allocation costs. |
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* |
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< |
* <p>Suppose <tt>x</tt> is a queue known to contain only strings. |
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> |
* <p>Suppose {@code x} is a queue known to contain only strings. |
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* The following code can be used to dump the queue into a newly |
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< |
* allocated array of <tt>String</tt>: |
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> |
* allocated array of {@code String}: |
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* |
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< |
* <pre> |
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< |
* String[] y = x.toArray(new String[0]);</pre> |
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> |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
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|
* |
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< |
* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
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< |
* <tt>toArray()</tt>. |
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> |
* Note that {@code toArray(new Object[0])} is identical in function to |
| 441 |
> |
* {@code toArray()}. |
| 442 |
|
* |
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|
* @param a the array into which the elements of the queue are to |
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* be stored, if it is big enough; otherwise, a new array of the |
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* this queue |
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* @throws NullPointerException if the specified array is null |
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*/ |
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+ |
@SuppressWarnings("unchecked") |
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|
public <T> T[] toArray(T[] a) { |
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+ |
final int size = this.size; |
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|
if (a.length < size) |
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|
// Make a new array of a's runtime type, but my contents: |
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|
return (T[]) Arrays.copyOf(queue, size, a.getClass()); |
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< |
System.arraycopy(queue, 0, a, 0, size); |
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> |
System.arraycopy(queue, 0, a, 0, size); |
| 459 |
|
if (a.length > size) |
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|
a[size] = null; |
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|
return a; |
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|
* Index (into queue array) of element to be returned by |
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|
* subsequent call to next. |
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|
*/ |
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< |
private int cursor = 0; |
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> |
private int cursor; |
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|
|
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|
/** |
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|
* Index of element returned by most recent call to next, |
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|
* We expect that most iterations, even those involving removals, |
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|
* will not need to store elements in this field. |
| 498 |
|
*/ |
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< |
private ArrayDeque<E> forgetMeNot = null; |
| 499 |
> |
private ArrayDeque<E> forgetMeNot; |
| 500 |
|
|
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|
/** |
| 502 |
|
* Element returned by the most recent call to next iff that |
| 503 |
|
* element was drawn from the forgetMeNot list. |
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|
*/ |
| 505 |
< |
private E lastRetElt = null; |
| 505 |
> |
private E lastRetElt; |
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|
|
| 507 |
|
/** |
| 508 |
|
* The modCount value that the iterator believes that the backing |
| 516 |
|
(forgetMeNot != null && !forgetMeNot.isEmpty()); |
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|
} |
| 518 |
|
|
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+ |
@SuppressWarnings("unchecked") |
| 520 |
|
public E next() { |
| 521 |
|
if (expectedModCount != modCount) |
| 522 |
|
throw new ConcurrentModificationException(); |
| 541 |
|
cursor--; |
| 542 |
|
else { |
| 543 |
|
if (forgetMeNot == null) |
| 544 |
< |
forgetMeNot = new ArrayDeque<E>(); |
| 544 |
> |
forgetMeNot = new ArrayDeque<>(); |
| 545 |
|
forgetMeNot.add(moved); |
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|
} |
| 547 |
|
} else if (lastRetElt != null) { |
| 549 |
|
lastRetElt = null; |
| 550 |
|
} else { |
| 551 |
|
throw new IllegalStateException(); |
| 552 |
< |
} |
| 552 |
> |
} |
| 553 |
|
expectedModCount = modCount; |
| 554 |
|
} |
| 555 |
|
} |
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|
size = 0; |
| 570 |
|
} |
| 571 |
|
|
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+ |
@SuppressWarnings("unchecked") |
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|
public E poll() { |
| 574 |
|
if (size == 0) |
| 575 |
|
return null; |
| 595 |
|
* position before i. This fact is used by iterator.remove so as to |
| 596 |
|
* avoid missing traversing elements. |
| 597 |
|
*/ |
| 598 |
+ |
@SuppressWarnings("unchecked") |
| 599 |
|
private E removeAt(int i) { |
| 600 |
< |
assert i >= 0 && i < size; |
| 600 |
> |
// assert i >= 0 && i < size; |
| 601 |
|
modCount++; |
| 602 |
|
int s = --size; |
| 603 |
|
if (s == i) // removed last element |
| 634 |
|
siftUpComparable(k, x); |
| 635 |
|
} |
| 636 |
|
|
| 637 |
+ |
@SuppressWarnings("unchecked") |
| 638 |
|
private void siftUpComparable(int k, E x) { |
| 639 |
|
Comparable<? super E> key = (Comparable<? super E>) x; |
| 640 |
|
while (k > 0) { |
| 648 |
|
queue[k] = key; |
| 649 |
|
} |
| 650 |
|
|
| 651 |
+ |
@SuppressWarnings("unchecked") |
| 652 |
|
private void siftUpUsingComparator(int k, E x) { |
| 653 |
|
while (k > 0) { |
| 654 |
|
int parent = (k - 1) >>> 1; |
| 676 |
|
siftDownComparable(k, x); |
| 677 |
|
} |
| 678 |
|
|
| 679 |
+ |
@SuppressWarnings("unchecked") |
| 680 |
|
private void siftDownComparable(int k, E x) { |
| 681 |
|
Comparable<? super E> key = (Comparable<? super E>)x; |
| 682 |
|
int half = size >>> 1; // loop while a non-leaf |
| 695 |
|
queue[k] = key; |
| 696 |
|
} |
| 697 |
|
|
| 698 |
+ |
@SuppressWarnings("unchecked") |
| 699 |
|
private void siftDownUsingComparator(int k, E x) { |
| 700 |
|
int half = size >>> 1; |
| 701 |
|
while (k < half) { |
| 717 |
|
* Establishes the heap invariant (described above) in the entire tree, |
| 718 |
|
* assuming nothing about the order of the elements prior to the call. |
| 719 |
|
*/ |
| 720 |
+ |
@SuppressWarnings("unchecked") |
| 721 |
|
private void heapify() { |
| 722 |
|
for (int i = (size >>> 1) - 1; i >= 0; i--) |
| 723 |
|
siftDown(i, (E) queue[i]); |
| 737 |
|
} |
| 738 |
|
|
| 739 |
|
/** |
| 740 |
< |
* Saves the state of the instance to a stream (that |
| 676 |
< |
* is, serializes it). |
| 740 |
> |
* Saves this queue to a stream (that is, serializes it). |
| 741 |
|
* |
| 742 |
|
* @serialData The length of the array backing the instance is |
| 743 |
|
* emitted (int), followed by all of its elements |
| 744 |
|
* (each an {@code Object}) in the proper order. |
| 745 |
|
* @param s the stream |
| 746 |
+ |
* @throws java.io.IOException if an I/O error occurs |
| 747 |
|
*/ |
| 748 |
|
private void writeObject(java.io.ObjectOutputStream s) |
| 749 |
< |
throws java.io.IOException{ |
| 749 |
> |
throws java.io.IOException { |
| 750 |
|
// Write out element count, and any hidden stuff |
| 751 |
|
s.defaultWriteObject(); |
| 752 |
|
|
| 763 |
|
* (that is, deserializes it). |
| 764 |
|
* |
| 765 |
|
* @param s the stream |
| 766 |
+ |
* @throws ClassNotFoundException if the class of a serialized object |
| 767 |
+ |
* could not be found |
| 768 |
+ |
* @throws java.io.IOException if an I/O error occurs |
| 769 |
|
*/ |
| 770 |
|
private void readObject(java.io.ObjectInputStream s) |
| 771 |
|
throws java.io.IOException, ClassNotFoundException { |
| 775 |
|
// Read in (and discard) array length |
| 776 |
|
s.readInt(); |
| 777 |
|
|
| 778 |
< |
queue = new Object[size]; |
| 778 |
> |
queue = new Object[size]; |
| 779 |
|
|
| 780 |
|
// Read in all elements. |
| 781 |
|
for (int i = 0; i < size; i++) |
| 782 |
|
queue[i] = s.readObject(); |
| 783 |
|
|
| 784 |
< |
// Elements are guaranteed to be in "proper order", but the |
| 785 |
< |
// spec has never explained what that might be. |
| 786 |
< |
heapify(); |
| 784 |
> |
// Elements are guaranteed to be in "proper order", but the |
| 785 |
> |
// spec has never explained what that might be. |
| 786 |
> |
heapify(); |
| 787 |
> |
} |
| 788 |
> |
|
| 789 |
> |
public Spliterator<E> spliterator() { |
| 790 |
> |
return new PriorityQueueSpliterator<E>(this, 0, -1, 0); |
| 791 |
> |
} |
| 792 |
> |
|
| 793 |
> |
/** |
| 794 |
> |
* This is very similar to ArrayList Spliterator, except for extra |
| 795 |
> |
* null checks. |
| 796 |
> |
*/ |
| 797 |
> |
static final class PriorityQueueSpliterator<E> implements Spliterator<E> { |
| 798 |
> |
private final PriorityQueue<E> pq; |
| 799 |
> |
private int index; // current index, modified on advance/split |
| 800 |
> |
private int fence; // -1 until first use |
| 801 |
> |
private int expectedModCount; // initialized when fence set |
| 802 |
> |
|
| 803 |
> |
/** Creates new spliterator covering the given range */ |
| 804 |
> |
PriorityQueueSpliterator(PriorityQueue<E> pq, int origin, int fence, |
| 805 |
> |
int expectedModCount) { |
| 806 |
> |
this.pq = pq; |
| 807 |
> |
this.index = origin; |
| 808 |
> |
this.fence = fence; |
| 809 |
> |
this.expectedModCount = expectedModCount; |
| 810 |
> |
} |
| 811 |
> |
|
| 812 |
> |
private int getFence() { // initialize fence to size on first use |
| 813 |
> |
int hi; |
| 814 |
> |
if ((hi = fence) < 0) { |
| 815 |
> |
expectedModCount = pq.modCount; |
| 816 |
> |
hi = fence = pq.size; |
| 817 |
> |
} |
| 818 |
> |
return hi; |
| 819 |
> |
} |
| 820 |
> |
|
| 821 |
> |
public Spliterator<E> trySplit() { |
| 822 |
> |
int hi = getFence(), lo = index, mid = (lo + hi) >>> 1; |
| 823 |
> |
return (lo >= mid) ? null : |
| 824 |
> |
new PriorityQueueSpliterator<E>(pq, lo, index = mid, |
| 825 |
> |
expectedModCount); |
| 826 |
> |
} |
| 827 |
> |
|
| 828 |
> |
@SuppressWarnings("unchecked") |
| 829 |
> |
public void forEachRemaining(Consumer<? super E> action) { |
| 830 |
> |
int i, hi, mc; // hoist accesses and checks from loop |
| 831 |
> |
PriorityQueue<E> q; Object[] a; |
| 832 |
> |
if (action == null) |
| 833 |
> |
throw new NullPointerException(); |
| 834 |
> |
if ((q = pq) != null && (a = q.queue) != null) { |
| 835 |
> |
if ((hi = fence) < 0) { |
| 836 |
> |
mc = q.modCount; |
| 837 |
> |
hi = q.size; |
| 838 |
> |
} |
| 839 |
> |
else |
| 840 |
> |
mc = expectedModCount; |
| 841 |
> |
if ((i = index) >= 0 && (index = hi) <= a.length) { |
| 842 |
> |
for (E e;; ++i) { |
| 843 |
> |
if (i < hi) { |
| 844 |
> |
if ((e = (E) a[i]) == null) // must be CME |
| 845 |
> |
break; |
| 846 |
> |
action.accept(e); |
| 847 |
> |
} |
| 848 |
> |
else if (q.modCount != mc) |
| 849 |
> |
break; |
| 850 |
> |
else |
| 851 |
> |
return; |
| 852 |
> |
} |
| 853 |
> |
} |
| 854 |
> |
} |
| 855 |
> |
throw new ConcurrentModificationException(); |
| 856 |
> |
} |
| 857 |
> |
|
| 858 |
> |
public boolean tryAdvance(Consumer<? super E> action) { |
| 859 |
> |
int hi = getFence(), lo = index; |
| 860 |
> |
if (lo >= 0 && lo < hi) { |
| 861 |
> |
index = lo + 1; |
| 862 |
> |
@SuppressWarnings("unchecked") E e = (E)pq.queue[lo]; |
| 863 |
> |
if (e == null) |
| 864 |
> |
throw new ConcurrentModificationException(); |
| 865 |
> |
action.accept(e); |
| 866 |
> |
if (pq.modCount != expectedModCount) |
| 867 |
> |
throw new ConcurrentModificationException(); |
| 868 |
> |
return true; |
| 869 |
> |
} |
| 870 |
> |
return false; |
| 871 |
> |
} |
| 872 |
> |
|
| 873 |
> |
public long estimateSize() { |
| 874 |
> |
return (long) (getFence() - index); |
| 875 |
> |
} |
| 876 |
> |
|
| 877 |
> |
public int characteristics() { |
| 878 |
> |
return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL; |
| 879 |
> |
} |
| 880 |
|
} |
| 881 |
|
} |
