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package java.util; |
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/* |
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* @(#)PriorityQueue.java 1.8 05/08/27 |
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* |
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* Copyright 2005 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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import java.util.*; |
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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 (resizable) priority queue based on a priority |
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* heap.The take operation returns the least element with respect to |
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* the given ordering. (If more than one element is tied for least |
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* value, one of them is arbitrarily chosen to be returned -- no |
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* guarantees are made for ordering across ties.) Ordering follows the |
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* java.util.Collection conventions: Either the elements must be |
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* Comparable, or a Comparator must be supplied. Comparison failures |
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* throw ClassCastExceptions during insertions and extractions. |
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**/ |
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public class PriorityQueue<E> extends AbstractCollection<E> implements Queue<E> { |
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public PriorityQueue(int initialCapacity) {} |
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public PriorityQueue(int initialCapacity, Comparator comparator) {} |
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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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* |
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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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* 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()} 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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* |
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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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* 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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* |
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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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* Java Collections Framework</a>. |
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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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* @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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implements java.io.Serializable { |
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public PriorityQueue(int initialCapacity, Collection initialElements) {} |
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private static final long serialVersionUID = -7720805057305804111L; |
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public PriorityQueue(int initialCapacity, Comparator comparator, Collection initialElements) {} |
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private static final int DEFAULT_INITIAL_CAPACITY = 11; |
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public boolean add(E x) { |
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return false; |
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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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private transient Object[] queue; |
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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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|
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/** |
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* The comparator, or null if priority queue uses elements' |
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* natural ordering. |
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*/ |
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private final Comparator<? super E> comparator; |
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|
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/** |
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* The number of times this priority queue has been |
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* <i>structurally modified</i>. See AbstractList for gory details. |
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*/ |
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private transient int modCount = 0; |
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|
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/** |
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* Creates a <tt>PriorityQueue</tt> 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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public boolean offer(E x) { |
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return false; |
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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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* 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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*/ |
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public PriorityQueue(int initialCapacity) { |
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this(initialCapacity, null); |
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} |
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public boolean remove(Object x) { |
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return false; |
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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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* 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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* 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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public E remove() { |
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return null; |
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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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* |
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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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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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else { |
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comparator = null; |
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heapify(); |
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} |
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} |
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public Iterator<E> iterator() { |
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return 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 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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* 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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comparator = (Comparator<? super E>)c.comparator(); |
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initFromCollection(c); |
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} |
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public E element() { |
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return null; |
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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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* 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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comparator = (Comparator<? super E>)c.comparator(); |
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initFromCollection(c); |
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} |
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public E poll() { |
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return null; |
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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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* @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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} |
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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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// 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 * 3) / 2)); |
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if (newCapacity < minCapacity) |
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newCapacity = minCapacity; |
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queue = Arrays.copyOf(queue, newCapacity); |
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} |
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|
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/** |
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* Inserts the specified element into this priority queue. |
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* |
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* @return <tt>true</tt> (as specified by {@link Collection#add}) |
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* @throws ClassCastException if the specified element cannot be |
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* compared with elements currently in this priority queue |
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* according to the priority queue's ordering |
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* @throws NullPointerException if the specified element is null |
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*/ |
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public boolean add(E e) { |
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return offer(e); |
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} |
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|
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/** |
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* Inserts the specified element into this priority queue. |
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* |
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* @return <tt>true</tt> (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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size = i + 1; |
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if (i == 0) |
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queue[0] = e; |
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else |
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siftUp(i, e); |
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return true; |
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} |
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|
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public E peek() { |
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return null; |
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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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} |
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|
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< |
public boolean isEmpty() { |
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private int indexOf(Object o) { |
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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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} |
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return -1; |
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} |
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|
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/** |
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* Removes a single instance of the specified element from this queue, |
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* if it is present. More formally, removes an element <tt>e</tt> such |
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* that <tt>o.equals(e)</tt>, if this queue contains one or more such |
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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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* |
297 |
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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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*/ |
300 |
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public boolean remove(Object o) { |
301 |
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int i = indexOf(o); |
302 |
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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; |
307 |
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} |
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} |
309 |
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|
310 |
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/** |
311 |
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* Version of remove using reference equality, not equals. |
312 |
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* Needed by iterator.remove |
313 |
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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. |
316 |
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*/ |
317 |
> |
boolean removeEq(Object o) { |
318 |
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for (int i = 0; i < size; i++) { |
319 |
> |
if (o == queue[i]) { |
320 |
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removeAt(i); |
321 |
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return true; |
322 |
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} |
323 |
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} |
324 |
|
return false; |
325 |
|
} |
326 |
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public int size() { |
327 |
< |
return 0; |
326 |
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|
327 |
> |
/** |
328 |
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* Returns <tt>true</tt> if this queue contains the specified element. |
329 |
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* More formally, returns <tt>true</tt> if and only if this queue contains |
330 |
> |
* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>. |
331 |
> |
* |
332 |
> |
* @param o object to be checked for containment in this queue |
333 |
> |
* @return <tt>true</tt> if this queue contains the specified element |
334 |
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*/ |
335 |
> |
public boolean contains(Object o) { |
336 |
> |
return indexOf(o) != -1; |
337 |
|
} |
338 |
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|
339 |
+ |
/** |
340 |
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* Returns an array containing all of the elements in this queue, |
341 |
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* The elements are in no particular order. |
342 |
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* |
343 |
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* <p>The returned array will be "safe" in that no references to it are |
344 |
+ |
* maintained by this list. (In other words, this method must allocate |
345 |
+ |
* a new array). The caller is thus free to modify the returned array. |
346 |
+ |
* |
347 |
+ |
* @return an array containing all of the elements in this queue. |
348 |
+ |
*/ |
349 |
|
public Object[] toArray() { |
350 |
< |
return null; |
350 |
> |
return Arrays.copyOf(queue, size); |
351 |
> |
} |
352 |
> |
|
353 |
> |
/** |
354 |
> |
* Returns an array containing all of the elements in this queue. |
355 |
> |
* The elements are in no particular order. The runtime type of |
356 |
> |
* the returned array is that of the specified array. If the queue |
357 |
> |
* fits in the specified array, it is returned therein. |
358 |
> |
* Otherwise, a new array is allocated with the runtime type of |
359 |
> |
* the specified array and the size of this queue. |
360 |
> |
* |
361 |
> |
* <p>If the queue fits in the specified array with room to spare |
362 |
> |
* (i.e., the array has more elements than the queue), the element in |
363 |
> |
* the array immediately following the end of the collection is set to |
364 |
> |
* <tt>null</tt>. (This is useful in determining the length of the |
365 |
> |
* queue <i>only</i> if the caller knows that the queue does not contain |
366 |
> |
* any null elements.) |
367 |
> |
* |
368 |
> |
* @param a the array into which the elements of the queue are to |
369 |
> |
* be stored, if it is big enough; otherwise, a new array of the |
370 |
> |
* same runtime type is allocated for this purpose. |
371 |
> |
* @return an array containing the elements of the queue |
372 |
> |
* @throws ArrayStoreException if the runtime type of the specified array |
373 |
> |
* is not a supertype of the runtime type of every element in |
374 |
> |
* this queue |
375 |
> |
* @throws NullPointerException if the specified array is null |
376 |
> |
*/ |
377 |
> |
public <T> T[] toArray(T[] a) { |
378 |
> |
if (a.length < size) |
379 |
> |
// Make a new array of a's runtime type, but my contents: |
380 |
> |
return (T[]) Arrays.copyOf(queue, size, a.getClass()); |
381 |
> |
System.arraycopy(queue, 0, a, 0, size); |
382 |
> |
if (a.length > size) |
383 |
> |
a[size] = null; |
384 |
> |
return a; |
385 |
|
} |
386 |
|
|
387 |
< |
public <T> T[] toArray(T[] array) { |
387 |
> |
/** |
388 |
> |
* Returns an iterator over the elements in this queue. The iterator |
389 |
> |
* does not return the elements in any particular order. |
390 |
> |
* |
391 |
> |
* @return an iterator over the elements in this queue |
392 |
> |
*/ |
393 |
> |
public Iterator<E> iterator() { |
394 |
> |
return new Itr(); |
395 |
> |
} |
396 |
> |
|
397 |
> |
private final class Itr implements Iterator<E> { |
398 |
> |
/** |
399 |
> |
* Index (into queue array) of element to be returned by |
400 |
> |
* subsequent call to next. |
401 |
> |
*/ |
402 |
> |
private int cursor = 0; |
403 |
> |
|
404 |
> |
/** |
405 |
> |
* Index of element returned by most recent call to next, |
406 |
> |
* unless that element came from the forgetMeNot list. |
407 |
> |
* Set to -1 if element is deleted by a call to remove. |
408 |
> |
*/ |
409 |
> |
private int lastRet = -1; |
410 |
> |
|
411 |
> |
/** |
412 |
> |
* A queue of elements that were moved from the unvisited portion of |
413 |
> |
* the heap into the visited portion as a result of "unlucky" element |
414 |
> |
* removals during the iteration. (Unlucky element removals are those |
415 |
> |
* that require a siftup instead of a siftdown.) We must visit all of |
416 |
> |
* the elements in this list to complete the iteration. We do this |
417 |
> |
* after we've completed the "normal" iteration. |
418 |
> |
* |
419 |
> |
* We expect that most iterations, even those involving removals, |
420 |
> |
* will not use need to store elements in this field. |
421 |
> |
*/ |
422 |
> |
private ArrayDeque<E> forgetMeNot = null; |
423 |
> |
|
424 |
> |
/** |
425 |
> |
* Element returned by the most recent call to next iff that |
426 |
> |
* element was drawn from the forgetMeNot list. |
427 |
> |
*/ |
428 |
> |
private E lastRetElt = null; |
429 |
> |
|
430 |
> |
/** |
431 |
> |
* The modCount value that the iterator believes that the backing |
432 |
> |
* List should have. If this expectation is violated, the iterator |
433 |
> |
* has detected concurrent modification. |
434 |
> |
*/ |
435 |
> |
private int expectedModCount = modCount; |
436 |
> |
|
437 |
> |
public boolean hasNext() { |
438 |
> |
return cursor < size || |
439 |
> |
(forgetMeNot != null && !forgetMeNot.isEmpty()); |
440 |
> |
} |
441 |
> |
|
442 |
> |
public E next() { |
443 |
> |
if (expectedModCount != modCount) |
444 |
> |
throw new ConcurrentModificationException(); |
445 |
> |
if (cursor < size) |
446 |
> |
return (E) queue[lastRet = cursor++]; |
447 |
> |
if (forgetMeNot != null) { |
448 |
> |
lastRet = -1; |
449 |
> |
lastRetElt = forgetMeNot.poll(); |
450 |
> |
if (lastRetElt != null) |
451 |
> |
return lastRetElt; |
452 |
> |
} |
453 |
> |
throw new NoSuchElementException(); |
454 |
> |
} |
455 |
> |
|
456 |
> |
public void remove() { |
457 |
> |
if (expectedModCount != modCount) |
458 |
> |
throw new ConcurrentModificationException(); |
459 |
> |
if (lastRet == -1 && lastRetElt == null) |
460 |
> |
throw new IllegalStateException(); |
461 |
> |
if (lastRet != -1) { |
462 |
> |
E moved = PriorityQueue.this.removeAt(lastRet); |
463 |
> |
lastRet = -1; |
464 |
> |
if (moved == null) |
465 |
> |
cursor--; |
466 |
> |
else { |
467 |
> |
if (forgetMeNot == null) |
468 |
> |
forgetMeNot = new ArrayDeque<E>(); |
469 |
> |
forgetMeNot.add(moved); |
470 |
> |
} |
471 |
> |
} else { |
472 |
> |
PriorityQueue.this.removeEq(lastRetElt); |
473 |
> |
lastRetElt = null; |
474 |
> |
} |
475 |
> |
expectedModCount = modCount; |
476 |
> |
} |
477 |
> |
|
478 |
> |
} |
479 |
> |
|
480 |
> |
public int size() { |
481 |
> |
return size; |
482 |
> |
} |
483 |
> |
|
484 |
> |
/** |
485 |
> |
* Removes all of the elements from this priority queue. |
486 |
> |
* The queue will be empty after this call returns. |
487 |
> |
*/ |
488 |
> |
public void clear() { |
489 |
> |
modCount++; |
490 |
> |
for (int i = 0; i < size; i++) |
491 |
> |
queue[i] = null; |
492 |
> |
size = 0; |
493 |
> |
} |
494 |
> |
|
495 |
> |
public E poll() { |
496 |
> |
if (size == 0) |
497 |
> |
return null; |
498 |
> |
int s = --size; |
499 |
> |
modCount++; |
500 |
> |
E result = (E)queue[0]; |
501 |
> |
E x = (E)queue[s]; |
502 |
> |
queue[s] = null; |
503 |
> |
if (s != 0) |
504 |
> |
siftDown(0, x); |
505 |
> |
return result; |
506 |
> |
} |
507 |
> |
|
508 |
> |
/** |
509 |
> |
* Removes the ith element from queue. |
510 |
> |
* |
511 |
> |
* Normally this method leaves the elements at up to i-1, |
512 |
> |
* inclusive, untouched. Under these circumstances, it returns |
513 |
> |
* null. Occasionally, in order to maintain the heap invariant, |
514 |
> |
* it must swap a later element of the list with one earlier than |
515 |
> |
* i. Under these circumstances, this method returns the element |
516 |
> |
* that was previously at the end of the list and is now at some |
517 |
> |
* position before i. This fact is used by iterator.remove so as to |
518 |
> |
* avoid missing traverseing elements. |
519 |
> |
*/ |
520 |
> |
private E removeAt(int i) { |
521 |
> |
assert i >= 0 && i < size; |
522 |
> |
modCount++; |
523 |
> |
int s = --size; |
524 |
> |
if (s == i) // removed last element |
525 |
> |
queue[i] = null; |
526 |
> |
else { |
527 |
> |
E moved = (E) queue[s]; |
528 |
> |
queue[s] = null; |
529 |
> |
siftDown(i, moved); |
530 |
> |
if (queue[i] == moved) { |
531 |
> |
siftUp(i, moved); |
532 |
> |
if (queue[i] != moved) |
533 |
> |
return moved; |
534 |
> |
} |
535 |
> |
} |
536 |
|
return null; |
537 |
|
} |
538 |
|
|
539 |
+ |
/** |
540 |
+ |
* Inserts item x at position k, maintaining heap invariant by |
541 |
+ |
* promoting x up the tree until it is greater than or equal to |
542 |
+ |
* its parent, or is the root. |
543 |
+ |
* |
544 |
+ |
* To simplify and speed up coercions and comparisons. the |
545 |
+ |
* Comparable and Comparator versions are separated into different |
546 |
+ |
* methods that are otherwise identical. (Similarly for siftDown.) |
547 |
+ |
* |
548 |
+ |
* @param k the position to fill |
549 |
+ |
* @param x the item to insert |
550 |
+ |
*/ |
551 |
+ |
private void siftUp(int k, E x) { |
552 |
+ |
if (comparator != null) |
553 |
+ |
siftUpUsingComparator(k, x); |
554 |
+ |
else |
555 |
+ |
siftUpComparable(k, x); |
556 |
+ |
} |
557 |
+ |
|
558 |
+ |
private void siftUpComparable(int k, E x) { |
559 |
+ |
Comparable<? super E> key = (Comparable<? super E>) x; |
560 |
+ |
while (k > 0) { |
561 |
+ |
int parent = (k - 1) >>> 1; |
562 |
+ |
Object e = queue[parent]; |
563 |
+ |
if (key.compareTo((E)e) >= 0) |
564 |
+ |
break; |
565 |
+ |
queue[k] = e; |
566 |
+ |
k = parent; |
567 |
+ |
} |
568 |
+ |
queue[k] = key; |
569 |
+ |
} |
570 |
+ |
|
571 |
+ |
private void siftUpUsingComparator(int k, E x) { |
572 |
+ |
while (k > 0) { |
573 |
+ |
int parent = (k - 1) >>> 1; |
574 |
+ |
Object e = queue[parent]; |
575 |
+ |
if (comparator.compare(x, (E)e) >= 0) |
576 |
+ |
break; |
577 |
+ |
queue[k] = e; |
578 |
+ |
k = parent; |
579 |
+ |
} |
580 |
+ |
queue[k] = x; |
581 |
+ |
} |
582 |
+ |
|
583 |
+ |
/** |
584 |
+ |
* Inserts item x at position k, maintaining heap invariant by |
585 |
+ |
* demoting x down the tree repeatedly until it is less than or |
586 |
+ |
* equal to its children or is a leaf. |
587 |
+ |
* |
588 |
+ |
* @param k the position to fill |
589 |
+ |
* @param x the item to insert |
590 |
+ |
*/ |
591 |
+ |
private void siftDown(int k, E x) { |
592 |
+ |
if (comparator != null) |
593 |
+ |
siftDownUsingComparator(k, x); |
594 |
+ |
else |
595 |
+ |
siftDownComparable(k, x); |
596 |
+ |
} |
597 |
+ |
|
598 |
+ |
private void siftDownComparable(int k, E x) { |
599 |
+ |
Comparable<? super E> key = (Comparable<? super E>)x; |
600 |
+ |
int half = size >>> 1; // loop while a non-leaf |
601 |
+ |
while (k < half) { |
602 |
+ |
int child = (k << 1) + 1; // assume left child is least |
603 |
+ |
Object c = queue[child]; |
604 |
+ |
int right = child + 1; |
605 |
+ |
if (right < size && |
606 |
+ |
((Comparable<? super E>)c).compareTo((E)queue[right]) > 0) |
607 |
+ |
c = queue[child = right]; |
608 |
+ |
if (key.compareTo((E)c) <= 0) |
609 |
+ |
break; |
610 |
+ |
queue[k] = c; |
611 |
+ |
k = child; |
612 |
+ |
} |
613 |
+ |
queue[k] = key; |
614 |
+ |
} |
615 |
+ |
|
616 |
+ |
private void siftDownUsingComparator(int k, E x) { |
617 |
+ |
int half = size >>> 1; |
618 |
+ |
while (k < half) { |
619 |
+ |
int child = (k << 1) + 1; |
620 |
+ |
Object c = queue[child]; |
621 |
+ |
int right = child + 1; |
622 |
+ |
if (right < size && |
623 |
+ |
comparator.compare((E)c, (E)queue[right]) > 0) |
624 |
+ |
c = queue[child = right]; |
625 |
+ |
if (comparator.compare(x, (E)c) <= 0) |
626 |
+ |
break; |
627 |
+ |
queue[k] = c; |
628 |
+ |
k = child; |
629 |
+ |
} |
630 |
+ |
queue[k] = x; |
631 |
+ |
} |
632 |
+ |
|
633 |
+ |
/** |
634 |
+ |
* Establishes the heap invariant (described above) in the entire tree, |
635 |
+ |
* assuming nothing about the order of the elements prior to the call. |
636 |
+ |
*/ |
637 |
+ |
private void heapify() { |
638 |
+ |
for (int i = (size >>> 1) - 1; i >= 0; i--) |
639 |
+ |
siftDown(i, (E)queue[i]); |
640 |
+ |
} |
641 |
+ |
|
642 |
+ |
/** |
643 |
+ |
* Returns the comparator used to order the elements in this |
644 |
+ |
* queue, or <tt>null</tt> if this queue is sorted according to |
645 |
+ |
* the {@linkplain Comparable natural ordering} of its elements. |
646 |
+ |
* |
647 |
+ |
* @return the comparator used to order this queue, or |
648 |
+ |
* <tt>null</tt> if this queue is sorted according to the |
649 |
+ |
* natural ordering of its elements. |
650 |
+ |
*/ |
651 |
+ |
public Comparator<? super E> comparator() { |
652 |
+ |
return comparator; |
653 |
+ |
} |
654 |
+ |
|
655 |
+ |
/** |
656 |
+ |
* Save the state of the instance to a stream (that |
657 |
+ |
* is, serialize it). |
658 |
+ |
* |
659 |
+ |
* @serialData The length of the array backing the instance is |
660 |
+ |
* emitted (int), followed by all of its elements (each an |
661 |
+ |
* <tt>Object</tt>) in the proper order. |
662 |
+ |
* @param s the stream |
663 |
+ |
*/ |
664 |
+ |
private void writeObject(java.io.ObjectOutputStream s) |
665 |
+ |
throws java.io.IOException{ |
666 |
+ |
// Write out element count, and any hidden stuff |
667 |
+ |
s.defaultWriteObject(); |
668 |
+ |
|
669 |
+ |
// Write out array length |
670 |
+ |
// For compatibility with 1.5 version, must be at least 2. |
671 |
+ |
s.writeInt(Math.max(2, queue.length)); |
672 |
+ |
|
673 |
+ |
// Write out all elements in the proper order. |
674 |
+ |
for (int i=0; i<size; i++) |
675 |
+ |
s.writeObject(queue[i]); |
676 |
+ |
} |
677 |
+ |
|
678 |
+ |
/** |
679 |
+ |
* Reconstitute the <tt>PriorityQueue</tt> instance from a stream |
680 |
+ |
* (that is, deserialize it). |
681 |
+ |
* @param s the stream |
682 |
+ |
*/ |
683 |
+ |
private void readObject(java.io.ObjectInputStream s) |
684 |
+ |
throws java.io.IOException, ClassNotFoundException { |
685 |
+ |
// Read in size, and any hidden stuff |
686 |
+ |
s.defaultReadObject(); |
687 |
+ |
|
688 |
+ |
// Read in array length and allocate array |
689 |
+ |
int arrayLength = s.readInt(); |
690 |
+ |
queue = new Object[arrayLength]; |
691 |
+ |
|
692 |
+ |
// Read in all elements in the proper order. |
693 |
+ |
for (int i=0; i<size; i++) |
694 |
+ |
queue[i] = (E) s.readObject(); |
695 |
+ |
} |
696 |
+ |
|
697 |
|
} |