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/* |
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* %W% %E% |
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* |
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* Copyright 2005 Sun Microsystems, Inc. All rights reserved. |
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* Copyright 2007 Sun Microsystems, Inc. All rights reserved. |
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* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
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*/ |
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package java.util; |
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import java.util.*; // for javadoc (till 6280605 is fixed) |
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/** |
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* An unbounded priority {@linkplain Queue queue} based on a priority |
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* heap. The elements of the priority queue are ordered according to |
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* their {@linkplain Comparable natural ordering}, or by a {@link |
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* Comparator} provided at queue construction time, depending on which |
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* constructor is used. A priority queue does not permit |
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* <tt>null</tt> elements. A priority queue relying on natural |
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* ordering also does not permit insertion of non-comparable objects |
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* (doing so may result in <tt>ClassCastException</tt>). |
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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 <tt>poll</tt>, |
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* <tt>remove</tt>, <tt>peek</tt>, and <tt>element</tt> access the |
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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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* Iterator} interfaces. The Iterator provided in method {@link |
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* #iterator()} is <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 <tt>Arrays.sort(pq.toArray())</tt>. |
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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 <tt>PriorityQueue</tt> |
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* instance concurrently if any of the threads modifies the list |
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* structurally. Instead, use the thread-safe {@link |
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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 O(log(n)) time |
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* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>, |
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* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the |
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* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and |
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* constant time for the retrieval methods (<tt>peek</tt>, |
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* <tt>element</tt>, and <tt>size</tt>). |
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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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* ({@code offer}, {@code poll}, {@code remove()} and {@code add}); |
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* linear time for the {@code remove(Object)} and {@code contains(Object)} |
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* methods; and constant time for the retrieval methods |
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* ({@code peek}, {@code element}, and {@code size}). |
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* |
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* <p>This class is a member of the |
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* <a href="{@docRoot}/../guide/collections/index.html"> |
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* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
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* Java Collections Framework</a>. |
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* |
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* @since 1.5 |
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* @version 1.8, 08/27/05 |
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* @author Josh Bloch |
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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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*/ |
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public class PriorityQueue<E> extends AbstractQueue<E> |
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private transient int modCount = 0; |
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/** |
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* Creates a <tt>PriorityQueue</tt> with the default initial |
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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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} |
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/** |
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* Creates a <tt>PriorityQueue</tt> with the specified initial |
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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 <tt>initialCapacity</tt> is less |
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* than 1 |
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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 <tt>PriorityQueue</tt> with the specified initial capacity |
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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 |
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* this priority queue. If <tt>null</tt>, the <i>natural |
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* ordering</i> of the elements will be used. |
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* @throws IllegalArgumentException if <tt>initialCapacity</tt> is |
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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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} |
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/** |
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* Creates a <tt>PriorityQueue</tt> containing the elements in the |
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* specified collection. If the specified collection is an |
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* instance of a {@link java.util.SortedSet} or is another |
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* <tt>PriorityQueue</tt>, the priority queue will be ordered |
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* according to the same ordering. Otherwise, this priority queue |
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* will be ordered according to the natural ordering of its elements. |
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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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} |
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/** |
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* Creates a <tt>PriorityQueue</tt> containing the elements in the |
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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 <tt>c</tt> cannot be |
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* compared to one another according to <tt>c</tt>'s |
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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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/** |
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* Creates a <tt>PriorityQueue</tt> containing the elements in the |
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* specified sorted set. This priority queue will be ordered |
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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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* 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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} |
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/** |
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* Initialize queue array with elements from the given Collection. |
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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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/** |
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* Inserts the specified element into this priority queue. |
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* |
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* @return <tt>true</tt> (as specified by {@link Collection#add}) |
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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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/** |
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* Inserts the specified element into this priority queue. |
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* |
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* @return <tt>true</tt> (as specified by {@link Queue#offer}) |
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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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|
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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 <tt>e</tt> such |
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* that <tt>o.equals(e)</tt>, if this queue contains one or more such |
297 |
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* elements. Returns true if this queue contained the specified element |
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* (or equivalently, if this queue changed as a result of the call). |
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* if it is present. More formally, removes an element {@code e} such |
296 |
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* that {@code o.equals(e)}, if this queue contains one or more such |
297 |
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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 <tt>true</tt> if this queue changed as a result of the call |
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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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/** |
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* Version of remove using reference equality, not equals. |
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* Needed by iterator.remove |
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* Needed by iterator.remove. |
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* |
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* @param o element to be removed from this queue, if present |
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* @return <tt>true</tt> if removed. |
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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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} |
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/** |
332 |
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* Returns <tt>true</tt> if this queue contains the specified element. |
333 |
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* More formally, returns <tt>true</tt> if and only if this queue contains |
334 |
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* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>. |
332 |
> |
* Returns {@code true} if this queue contains the specified element. |
333 |
> |
* More formally, returns {@code true} if and only if this queue contains |
334 |
> |
* 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 |
337 |
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* @return <tt>true</tt> if this queue contains the specified element |
337 |
> |
* @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; |
341 |
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} |
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/** |
344 |
< |
* Returns an array containing all of the elements in this queue, |
344 |
> |
* 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 |
348 |
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* maintained by this list. (In other words, this method must allocate |
348 |
> |
* maintained by this queue. (In other words, this method must allocate |
349 |
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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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* @return an array containing all of the elements in this queue. |
351 |
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* <p>This method acts as bridge between array-based and collection-based |
352 |
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* APIs. |
353 |
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* |
354 |
> |
* @return an array containing all of the elements in this queue |
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*/ |
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public Object[] toArray() { |
357 |
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return Arrays.copyOf(queue, size); |
358 |
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} |
359 |
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/** |
361 |
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* Returns an array containing all of the elements in this queue. |
362 |
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* The elements are in no particular order. The runtime type of |
363 |
< |
* the returned array is that of the specified array. If the queue |
364 |
< |
* fits in the specified array, it is returned therein. |
365 |
< |
* Otherwise, a new array is allocated with the runtime type of |
366 |
< |
* the specified array and the size of this queue. |
361 |
> |
* Returns an array containing all of the elements in this queue; the |
362 |
> |
* runtime type of the returned array is that of the specified array. |
363 |
> |
* The returned array elements are in no particular order. |
364 |
> |
* If the queue fits in the specified array, it is returned therein. |
365 |
> |
* Otherwise, a new array is allocated with the runtime type of the |
366 |
> |
* specified array and the size of this queue. |
367 |
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* |
368 |
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* <p>If the queue fits in the specified array with room to spare |
369 |
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* (i.e., the array has more elements than the queue), the element in |
370 |
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* the array immediately following the end of the collection is set to |
371 |
< |
* <tt>null</tt>. (This is useful in determining the length of the |
372 |
< |
* queue <i>only</i> if the caller knows that the queue does not contain |
373 |
< |
* any null elements.) |
371 |
> |
* {@code null}. |
372 |
> |
* |
373 |
> |
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
374 |
> |
* array-based and collection-based APIs. Further, this method allows |
375 |
> |
* precise control over the runtime type of the output array, and may, |
376 |
> |
* under certain circumstances, be used to save allocation costs. |
377 |
> |
* |
378 |
> |
* <p>Suppose <tt>x</tt> is a queue known to contain only strings. |
379 |
> |
* The following code can be used to dump the queue into a newly |
380 |
> |
* allocated array of <tt>String</tt>: |
381 |
> |
* |
382 |
> |
* <pre> |
383 |
> |
* String[] y = x.toArray(new String[0]);</pre> |
384 |
> |
* |
385 |
> |
* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
386 |
> |
* <tt>toArray()</tt>. |
387 |
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* |
388 |
|
* @param a the array into which the elements of the queue are to |
389 |
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* be stored, if it is big enough; otherwise, a new array of the |
390 |
|
* same runtime type is allocated for this purpose. |
391 |
< |
* @return an array containing the elements of the queue |
391 |
> |
* @return an array containing all of the elements in this queue |
392 |
|
* @throws ArrayStoreException if the runtime type of the specified array |
393 |
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* is not a supertype of the runtime type of every element in |
394 |
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* this queue |
437 |
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* after we've completed the "normal" iteration. |
438 |
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* |
439 |
|
* We expect that most iterations, even those involving removals, |
440 |
< |
* will not use need to store elements in this field. |
440 |
> |
* will not need to store elements in this field. |
441 |
|
*/ |
442 |
|
private ArrayDeque<E> forgetMeNot = null; |
443 |
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|
449 |
|
|
450 |
|
/** |
451 |
|
* The modCount value that the iterator believes that the backing |
452 |
< |
* List should have. If this expectation is violated, the iterator |
452 |
> |
* Queue should have. If this expectation is violated, the iterator |
453 |
|
* has detected concurrent modification. |
454 |
|
*/ |
455 |
|
private int expectedModCount = modCount; |
476 |
|
public void remove() { |
477 |
|
if (expectedModCount != modCount) |
478 |
|
throw new ConcurrentModificationException(); |
461 |
– |
if (lastRet == -1 && lastRetElt == null) |
462 |
– |
throw new IllegalStateException(); |
479 |
|
if (lastRet != -1) { |
480 |
|
E moved = PriorityQueue.this.removeAt(lastRet); |
481 |
|
lastRet = -1; |
486 |
|
forgetMeNot = new ArrayDeque<E>(); |
487 |
|
forgetMeNot.add(moved); |
488 |
|
} |
489 |
< |
} else { |
489 |
> |
} else if (lastRetElt != null) { |
490 |
|
PriorityQueue.this.removeEq(lastRetElt); |
491 |
|
lastRetElt = null; |
492 |
< |
} |
492 |
> |
} else { |
493 |
> |
throw new IllegalStateException(); |
494 |
> |
} |
495 |
|
expectedModCount = modCount; |
496 |
|
} |
479 |
– |
|
497 |
|
} |
498 |
|
|
499 |
|
public int size() { |
516 |
|
return null; |
517 |
|
int s = --size; |
518 |
|
modCount++; |
519 |
< |
E result = (E)queue[0]; |
520 |
< |
E x = (E)queue[s]; |
519 |
> |
E result = (E) queue[0]; |
520 |
> |
E x = (E) queue[s]; |
521 |
|
queue[s] = null; |
522 |
|
if (s != 0) |
523 |
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siftDown(0, x); |
534 |
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* i. Under these circumstances, this method returns the element |
535 |
|
* that was previously at the end of the list and is now at some |
536 |
|
* position before i. This fact is used by iterator.remove so as to |
537 |
< |
* avoid missing traverseing elements. |
537 |
> |
* avoid missing traversing elements. |
538 |
|
*/ |
539 |
|
private E removeAt(int i) { |
540 |
|
assert i >= 0 && i < size; |
579 |
|
while (k > 0) { |
580 |
|
int parent = (k - 1) >>> 1; |
581 |
|
Object e = queue[parent]; |
582 |
< |
if (key.compareTo((E)e) >= 0) |
582 |
> |
if (key.compareTo((E) e) >= 0) |
583 |
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break; |
584 |
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queue[k] = e; |
585 |
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k = parent; |
591 |
|
while (k > 0) { |
592 |
|
int parent = (k - 1) >>> 1; |
593 |
|
Object e = queue[parent]; |
594 |
< |
if (comparator.compare(x, (E)e) >= 0) |
594 |
> |
if (comparator.compare(x, (E) e) >= 0) |
595 |
|
break; |
596 |
|
queue[k] = e; |
597 |
|
k = parent; |
622 |
|
Object c = queue[child]; |
623 |
|
int right = child + 1; |
624 |
|
if (right < size && |
625 |
< |
((Comparable<? super E>)c).compareTo((E)queue[right]) > 0) |
625 |
> |
((Comparable<? super E>) c).compareTo((E) queue[right]) > 0) |
626 |
|
c = queue[child = right]; |
627 |
< |
if (key.compareTo((E)c) <= 0) |
627 |
> |
if (key.compareTo((E) c) <= 0) |
628 |
|
break; |
629 |
|
queue[k] = c; |
630 |
|
k = child; |
639 |
|
Object c = queue[child]; |
640 |
|
int right = child + 1; |
641 |
|
if (right < size && |
642 |
< |
comparator.compare((E)c, (E)queue[right]) > 0) |
642 |
> |
comparator.compare((E) c, (E) queue[right]) > 0) |
643 |
|
c = queue[child = right]; |
644 |
< |
if (comparator.compare(x, (E)c) <= 0) |
644 |
> |
if (comparator.compare(x, (E) c) <= 0) |
645 |
|
break; |
646 |
|
queue[k] = c; |
647 |
|
k = child; |
655 |
|
*/ |
656 |
|
private void heapify() { |
657 |
|
for (int i = (size >>> 1) - 1; i >= 0; i--) |
658 |
< |
siftDown(i, (E)queue[i]); |
658 |
> |
siftDown(i, (E) queue[i]); |
659 |
|
} |
660 |
|
|
661 |
|
/** |
662 |
|
* Returns the comparator used to order the elements in this |
663 |
< |
* queue, or <tt>null</tt> if this queue is sorted according to |
663 |
> |
* queue, or {@code null} if this queue is sorted according to |
664 |
|
* the {@linkplain Comparable natural ordering} of its elements. |
665 |
|
* |
666 |
|
* @return the comparator used to order this queue, or |
667 |
< |
* <tt>null</tt> if this queue is sorted according to the |
668 |
< |
* natural ordering of its elements. |
667 |
> |
* {@code null} if this queue is sorted according to the |
668 |
> |
* natural ordering of its elements |
669 |
|
*/ |
670 |
|
public Comparator<? super E> comparator() { |
671 |
|
return comparator; |
672 |
|
} |
673 |
|
|
674 |
|
/** |
675 |
< |
* Save the state of the instance to a stream (that |
676 |
< |
* is, serialize it). |
675 |
> |
* Saves the state of the instance to a stream (that |
676 |
> |
* is, serializes it). |
677 |
|
* |
678 |
|
* @serialData The length of the array backing the instance is |
679 |
< |
* emitted (int), followed by all of its elements (each an |
680 |
< |
* <tt>Object</tt>) in the proper order. |
679 |
> |
* emitted (int), followed by all of its elements |
680 |
> |
* (each an {@code Object}) in the proper order. |
681 |
|
* @param s the stream |
682 |
|
*/ |
683 |
|
private void writeObject(java.io.ObjectOutputStream s) |
685 |
|
// Write out element count, and any hidden stuff |
686 |
|
s.defaultWriteObject(); |
687 |
|
|
688 |
< |
// Write out array length |
689 |
< |
// For compatibility with 1.5 version, must be at least 2. |
673 |
< |
s.writeInt(Math.max(2, queue.length)); |
688 |
> |
// Write out array length, for compatibility with 1.5 version |
689 |
> |
s.writeInt(Math.max(2, size + 1)); |
690 |
|
|
691 |
< |
// Write out all elements in the proper order. |
692 |
< |
for (int i=0; i<size; i++) |
691 |
> |
// Write out all elements in the "proper order". |
692 |
> |
for (int i = 0; i < size; i++) |
693 |
|
s.writeObject(queue[i]); |
694 |
|
} |
695 |
|
|
696 |
|
/** |
697 |
< |
* Reconstitute the <tt>PriorityQueue</tt> instance from a stream |
698 |
< |
* (that is, deserialize it). |
697 |
> |
* Reconstitutes the {@code PriorityQueue} instance from a stream |
698 |
> |
* (that is, deserializes it). |
699 |
> |
* |
700 |
|
* @param s the stream |
701 |
|
*/ |
702 |
|
private void readObject(java.io.ObjectInputStream s) |
704 |
|
// Read in size, and any hidden stuff |
705 |
|
s.defaultReadObject(); |
706 |
|
|
707 |
< |
// Read in array length and allocate array |
708 |
< |
int arrayLength = s.readInt(); |
709 |
< |
queue = new Object[arrayLength]; |
710 |
< |
|
694 |
< |
// Read in all elements in the proper order. |
695 |
< |
for (int i=0; i<size; i++) |
696 |
< |
queue[i] = (E) s.readObject(); |
697 |
< |
} |
707 |
> |
// Read in (and discard) array length |
708 |
> |
s.readInt(); |
709 |
> |
|
710 |
> |
queue = new Object[size]; |
711 |
|
|
712 |
+ |
// Read in all elements. |
713 |
+ |
for (int i = 0; i < size; i++) |
714 |
+ |
queue[i] = s.readObject(); |
715 |
+ |
|
716 |
+ |
// Elements are guaranteed to be in "proper order", but the |
717 |
+ |
// spec has never explained what that might be. |
718 |
+ |
heapify(); |
719 |
+ |
} |
720 |
|
} |