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dl |
1.38 |
/* |
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* %W% %E% |
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* |
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jsr166 |
1.48 |
* Copyright 2004 Sun Microsystems, Inc. All rights reserved. |
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dl |
1.38 |
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
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*/ |
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package java.util; |
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tim |
1.1 |
|
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/** |
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dl |
1.41 |
* An unbounded priority {@linkplain Queue queue} based on a priority |
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* heap. This queue orders elements according to an order specified |
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* at construction time, which is specified either according to their |
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* <i>natural order</i> (see {@link Comparable}), or according to a |
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* {@link java.util.Comparator}, depending on which constructor is |
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* used. A priority queue does not permit <tt>null</tt> elements. |
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dl |
1.42 |
* A priority queue relying on natural ordering also does not |
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dl |
1.43 |
* permit insertion of non-comparable objects (doing so may result |
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dl |
1.42 |
* in <tt>ClassCastException</tt>). |
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dl |
1.40 |
* |
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dl |
1.41 |
* <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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dl |
1.42 |
* 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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tim |
1.14 |
* |
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dl |
1.41 |
* <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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dl |
1.40 |
* 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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tim |
1.2 |
* |
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dl |
1.41 |
* <p>This class implements all of the <em>optional</em> methods of |
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* the {@link Collection} and {@link Iterator} interfaces. The |
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* Iterator provided in method {@link #iterator()} is <em>not</em> |
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dl |
1.29 |
* guaranteed to traverse the elements of the PriorityQueue in any |
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* particular order. If you need ordered traversal, consider using |
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* <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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dholmes |
1.34 |
* java.util.concurrent.PriorityBlockingQueue} class. |
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dl |
1.29 |
* |
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* |
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dholmes |
1.11 |
* <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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tim |
1.2 |
* |
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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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dl |
1.7 |
* @since 1.5 |
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dl |
1.38 |
* @version %I%, %G% |
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dl |
1.7 |
* @author Josh Bloch |
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dl |
1.45 |
* @param <E> the type of elements held in this collection |
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tim |
1.2 |
*/ |
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public class PriorityQueue<E> extends AbstractQueue<E> |
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dl |
1.47 |
implements java.io.Serializable { |
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dholmes |
1.11 |
|
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dl |
1.31 |
private static final long serialVersionUID = -7720805057305804111L; |
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dl |
1.30 |
|
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tim |
1.2 |
private static final int DEFAULT_INITIAL_CAPACITY = 11; |
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tim |
1.1 |
|
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tim |
1.2 |
/** |
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* Priority queue represented as a balanced binary heap: the two children |
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* of queue[n] are queue[2*n] and queue[2*n + 1]. The priority queue is |
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* ordered by comparator, or by the elements' natural ordering, if |
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brian |
1.6 |
* comparator is null: For each node n in the heap and each descendant d |
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* of n, n <= d. |
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tim |
1.2 |
* |
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brian |
1.6 |
* The element with the lowest value is in queue[1], assuming the queue is |
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* nonempty. (A one-based array is used in preference to the traditional |
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* zero-based array to simplify parent and child calculations.) |
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tim |
1.2 |
* |
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* queue.length must be >= 2, even if size == 0. |
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*/ |
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tim |
1.16 |
private transient Object[] queue; |
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tim |
1.1 |
|
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tim |
1.2 |
/** |
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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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tim |
1.1 |
|
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tim |
1.2 |
/** |
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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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tim |
1.16 |
private final Comparator<? super E> comparator; |
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tim |
1.2 |
|
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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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dl |
1.5 |
private transient int modCount = 0; |
102 |
tim |
1.2 |
|
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/** |
104 |
dholmes |
1.21 |
* Creates a <tt>PriorityQueue</tt> with the default initial capacity |
105 |
dl |
1.7 |
* (11) that orders its elements according to their natural |
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tim |
1.24 |
* ordering (using <tt>Comparable</tt>). |
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tim |
1.2 |
*/ |
108 |
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public PriorityQueue() { |
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dholmes |
1.11 |
this(DEFAULT_INITIAL_CAPACITY, null); |
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tim |
1.1 |
} |
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tim |
1.2 |
|
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/** |
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dholmes |
1.21 |
* Creates a <tt>PriorityQueue</tt> with the specified initial capacity |
114 |
dl |
1.7 |
* that orders its elements according to their natural ordering |
115 |
tim |
1.24 |
* (using <tt>Comparable</tt>). |
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tim |
1.2 |
* |
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* @param initialCapacity the initial capacity for this priority queue. |
118 |
dholmes |
1.23 |
* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less |
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* than 1 |
120 |
tim |
1.2 |
*/ |
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public PriorityQueue(int initialCapacity) { |
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this(initialCapacity, null); |
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tim |
1.1 |
} |
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tim |
1.2 |
|
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/** |
126 |
dholmes |
1.21 |
* Creates a <tt>PriorityQueue</tt> with the specified initial capacity |
127 |
tim |
1.2 |
* 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 used to order this priority queue. |
131 |
dholmes |
1.11 |
* If <tt>null</tt> then the order depends on the elements' natural |
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* ordering. |
133 |
dholmes |
1.15 |
* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less |
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* than 1 |
135 |
tim |
1.2 |
*/ |
136 |
dholmes |
1.23 |
public PriorityQueue(int initialCapacity, |
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Comparator<? super E> comparator) { |
138 |
tim |
1.2 |
if (initialCapacity < 1) |
139 |
dholmes |
1.15 |
throw new IllegalArgumentException(); |
140 |
tim |
1.16 |
this.queue = new Object[initialCapacity + 1]; |
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tim |
1.2 |
this.comparator = comparator; |
142 |
tim |
1.1 |
} |
143 |
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144 |
tim |
1.2 |
/** |
145 |
dl |
1.22 |
* Common code to initialize underlying queue array across |
146 |
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* constructors below. |
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*/ |
148 |
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private void initializeArray(Collection<? extends E> c) { |
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int sz = c.size(); |
150 |
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int initialCapacity = (int)Math.min((sz * 110L) / 100, |
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Integer.MAX_VALUE - 1); |
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if (initialCapacity < 1) |
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initialCapacity = 1; |
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this.queue = new Object[initialCapacity + 1]; |
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} |
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/** |
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* Initially fill elements of the queue array under the |
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* knowledge that it is sorted or is another PQ, in which |
161 |
dl |
1.36 |
* case we can just place the elements in the order presented. |
162 |
dl |
1.22 |
*/ |
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private void fillFromSorted(Collection<? extends E> c) { |
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for (Iterator<? extends E> i = c.iterator(); i.hasNext(); ) |
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queue[++size] = i.next(); |
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} |
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/** |
169 |
dl |
1.36 |
* Initially fill elements of the queue array that is not to our knowledge |
170 |
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* sorted, so we must rearrange the elements to guarantee the heap |
171 |
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* invariant. |
172 |
dl |
1.22 |
*/ |
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private void fillFromUnsorted(Collection<? extends E> c) { |
174 |
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for (Iterator<? extends E> i = c.iterator(); i.hasNext(); ) |
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dl |
1.36 |
queue[++size] = i.next(); |
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heapify(); |
177 |
dl |
1.22 |
} |
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179 |
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/** |
180 |
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* Creates a <tt>PriorityQueue</tt> containing the elements in the |
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* specified collection. The priority queue has an initial |
182 |
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* capacity of 110% of the size of the specified collection or 1 |
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* if the collection is empty. If the specified collection is an |
184 |
tim |
1.25 |
* instance of a {@link java.util.SortedSet} or is another |
185 |
dl |
1.22 |
* <tt>PriorityQueue</tt>, the priority queue will be sorted |
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* according to the same comparator, or according to its elements' |
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* natural order if the collection is sorted according to its |
188 |
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* elements' natural order. Otherwise, the priority queue is |
189 |
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* ordered according to its elements' natural order. |
190 |
tim |
1.2 |
* |
191 |
dholmes |
1.15 |
* @param c the collection whose elements are to be placed |
192 |
tim |
1.2 |
* into this priority queue. |
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* @throws ClassCastException if elements of the specified collection |
194 |
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* cannot be compared to one another according to the priority |
195 |
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* queue's ordering. |
196 |
dholmes |
1.15 |
* @throws NullPointerException if <tt>c</tt> or any element within it |
197 |
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* is <tt>null</tt> |
198 |
tim |
1.2 |
*/ |
199 |
tim |
1.16 |
public PriorityQueue(Collection<? extends E> c) { |
200 |
dl |
1.22 |
initializeArray(c); |
201 |
dl |
1.27 |
if (c instanceof SortedSet) { |
202 |
dl |
1.46 |
SortedSet<? extends E> s = (SortedSet<? extends E>)c; |
203 |
dl |
1.22 |
comparator = (Comparator<? super E>)s.comparator(); |
204 |
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fillFromSorted(s); |
205 |
dl |
1.27 |
} else if (c instanceof PriorityQueue) { |
206 |
dl |
1.22 |
PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c; |
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comparator = (Comparator<? super E>)s.comparator(); |
208 |
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fillFromSorted(s); |
209 |
tim |
1.26 |
} else { |
210 |
tim |
1.2 |
comparator = null; |
211 |
dl |
1.22 |
fillFromUnsorted(c); |
212 |
tim |
1.2 |
} |
213 |
dl |
1.22 |
} |
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215 |
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/** |
216 |
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* Creates a <tt>PriorityQueue</tt> containing the elements in the |
217 |
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* specified collection. The priority queue has an initial |
218 |
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* capacity of 110% of the size of the specified collection or 1 |
219 |
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* if the collection is empty. This priority queue will be sorted |
220 |
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* according to the same comparator as the given collection, or |
221 |
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* according to its elements' natural order if the collection is |
222 |
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* sorted according to its elements' natural order. |
223 |
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* |
224 |
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* @param c the collection whose elements are to be placed |
225 |
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* into this priority queue. |
226 |
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* @throws ClassCastException if elements of the specified collection |
227 |
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* cannot be compared to one another according to the priority |
228 |
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* queue's ordering. |
229 |
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* @throws NullPointerException if <tt>c</tt> or any element within it |
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* is <tt>null</tt> |
231 |
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*/ |
232 |
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public PriorityQueue(PriorityQueue<? extends E> c) { |
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initializeArray(c); |
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comparator = (Comparator<? super E>)c.comparator(); |
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fillFromSorted(c); |
236 |
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} |
237 |
dholmes |
1.18 |
|
238 |
dl |
1.22 |
/** |
239 |
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* Creates a <tt>PriorityQueue</tt> containing the elements in the |
240 |
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* specified collection. The priority queue has an initial |
241 |
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* capacity of 110% of the size of the specified collection or 1 |
242 |
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* if the collection is empty. This priority queue will be sorted |
243 |
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* according to the same comparator as the given collection, or |
244 |
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* according to its elements' natural order if the collection is |
245 |
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* sorted according to its elements' natural order. |
246 |
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* |
247 |
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* @param c the collection whose elements are to be placed |
248 |
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* into this priority queue. |
249 |
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* @throws ClassCastException if elements of the specified collection |
250 |
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* cannot be compared to one another according to the priority |
251 |
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* queue's ordering. |
252 |
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* @throws NullPointerException if <tt>c</tt> or any element within it |
253 |
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* is <tt>null</tt> |
254 |
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*/ |
255 |
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public PriorityQueue(SortedSet<? extends E> c) { |
256 |
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initializeArray(c); |
257 |
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comparator = (Comparator<? super E>)c.comparator(); |
258 |
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fillFromSorted(c); |
259 |
tim |
1.1 |
} |
260 |
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261 |
dl |
1.22 |
/** |
262 |
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* Resize array, if necessary, to be able to hold given index |
263 |
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*/ |
264 |
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private void grow(int index) { |
265 |
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int newlen = queue.length; |
266 |
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if (index < newlen) // don't need to grow |
267 |
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return; |
268 |
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if (index == Integer.MAX_VALUE) |
269 |
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throw new OutOfMemoryError(); |
270 |
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while (newlen <= index) { |
271 |
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if (newlen >= Integer.MAX_VALUE / 2) // avoid overflow |
272 |
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newlen = Integer.MAX_VALUE; |
273 |
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else |
274 |
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newlen <<= 2; |
275 |
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} |
276 |
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Object[] newQueue = new Object[newlen]; |
277 |
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System.arraycopy(queue, 0, newQueue, 0, queue.length); |
278 |
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queue = newQueue; |
279 |
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} |
280 |
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281 |
dl |
1.36 |
|
282 |
tim |
1.2 |
/** |
283 |
dl |
1.42 |
* Inserts the specified element into this priority queue. |
284 |
tim |
1.2 |
* |
285 |
dholmes |
1.11 |
* @return <tt>true</tt> |
286 |
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* @throws ClassCastException if the specified element cannot be compared |
287 |
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* with elements currently in the priority queue according |
288 |
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* to the priority queue's ordering. |
289 |
dholmes |
1.18 |
* @throws NullPointerException if the specified element is <tt>null</tt>. |
290 |
tim |
1.2 |
*/ |
291 |
dholmes |
1.18 |
public boolean offer(E o) { |
292 |
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if (o == null) |
293 |
dholmes |
1.11 |
throw new NullPointerException(); |
294 |
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modCount++; |
295 |
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++size; |
296 |
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|
297 |
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// Grow backing store if necessary |
298 |
dl |
1.22 |
if (size >= queue.length) |
299 |
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grow(size); |
300 |
dholmes |
1.11 |
|
301 |
dholmes |
1.18 |
queue[size] = o; |
302 |
dholmes |
1.11 |
fixUp(size); |
303 |
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return true; |
304 |
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} |
305 |
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|
306 |
dl |
1.40 |
public E peek() { |
307 |
tim |
1.2 |
if (size == 0) |
308 |
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return null; |
309 |
tim |
1.16 |
return (E) queue[1]; |
310 |
tim |
1.1 |
} |
311 |
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|
312 |
dholmes |
1.23 |
// Collection Methods - the first two override to update docs |
313 |
dholmes |
1.11 |
|
314 |
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/** |
315 |
dholmes |
1.23 |
* Adds the specified element to this queue. |
316 |
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* @return <tt>true</tt> (as per the general contract of |
317 |
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* <tt>Collection.add</tt>). |
318 |
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* |
319 |
dl |
1.40 |
* @throws NullPointerException if the specified element is <tt>null</tt>. |
320 |
dholmes |
1.15 |
* @throws ClassCastException if the specified element cannot be compared |
321 |
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* with elements currently in the priority queue according |
322 |
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* to the priority queue's ordering. |
323 |
dholmes |
1.11 |
*/ |
324 |
dholmes |
1.18 |
public boolean add(E o) { |
325 |
dl |
1.41 |
return offer(o); |
326 |
tim |
1.14 |
} |
327 |
dholmes |
1.11 |
|
328 |
dl |
1.49 |
/** |
329 |
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* Removes a single instance of the specified element from this |
330 |
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* collection, if it is present. |
331 |
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*/ |
332 |
dl |
1.12 |
public boolean remove(Object o) { |
333 |
dholmes |
1.11 |
if (o == null) |
334 |
dholmes |
1.15 |
return false; |
335 |
tim |
1.2 |
|
336 |
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if (comparator == null) { |
337 |
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for (int i = 1; i <= size; i++) { |
338 |
tim |
1.16 |
if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) { |
339 |
dl |
1.36 |
removeAt(i); |
340 |
tim |
1.2 |
return true; |
341 |
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} |
342 |
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} |
343 |
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} else { |
344 |
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for (int i = 1; i <= size; i++) { |
345 |
tim |
1.16 |
if (comparator.compare((E)queue[i], (E)o) == 0) { |
346 |
dl |
1.36 |
removeAt(i); |
347 |
tim |
1.2 |
return true; |
348 |
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} |
349 |
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} |
350 |
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} |
351 |
tim |
1.1 |
return false; |
352 |
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} |
353 |
tim |
1.2 |
|
354 |
dholmes |
1.23 |
/** |
355 |
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* Returns an iterator over the elements in this queue. The iterator |
356 |
|
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* does not return the elements in any particular order. |
357 |
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* |
358 |
|
|
* @return an iterator over the elements in this queue. |
359 |
|
|
*/ |
360 |
tim |
1.2 |
public Iterator<E> iterator() { |
361 |
dl |
1.7 |
return new Itr(); |
362 |
tim |
1.2 |
} |
363 |
|
|
|
364 |
|
|
private class Itr implements Iterator<E> { |
365 |
dl |
1.35 |
|
366 |
dl |
1.7 |
/** |
367 |
|
|
* Index (into queue array) of element to be returned by |
368 |
tim |
1.2 |
* subsequent call to next. |
369 |
dl |
1.7 |
*/ |
370 |
|
|
private int cursor = 1; |
371 |
tim |
1.2 |
|
372 |
dl |
1.7 |
/** |
373 |
dl |
1.36 |
* Index of element returned by most recent call to next, |
374 |
|
|
* unless that element came from the forgetMeNot list. |
375 |
|
|
* Reset to 0 if element is deleted by a call to remove. |
376 |
dl |
1.7 |
*/ |
377 |
|
|
private int lastRet = 0; |
378 |
|
|
|
379 |
|
|
/** |
380 |
|
|
* The modCount value that the iterator believes that the backing |
381 |
|
|
* List should have. If this expectation is violated, the iterator |
382 |
|
|
* has detected concurrent modification. |
383 |
|
|
*/ |
384 |
|
|
private int expectedModCount = modCount; |
385 |
tim |
1.2 |
|
386 |
dl |
1.36 |
/** |
387 |
|
|
* A list of elements that were moved from the unvisited portion of |
388 |
|
|
* the heap into the visited portion as a result of "unlucky" element |
389 |
|
|
* removals during the iteration. (Unlucky element removals are those |
390 |
|
|
* that require a fixup instead of a fixdown.) We must visit all of |
391 |
|
|
* the elements in this list to complete the iteration. We do this |
392 |
|
|
* after we've completed the "normal" iteration. |
393 |
|
|
* |
394 |
|
|
* We expect that most iterations, even those involving removals, |
395 |
|
|
* will not use need to store elements in this field. |
396 |
|
|
*/ |
397 |
|
|
private ArrayList<E> forgetMeNot = null; |
398 |
|
|
|
399 |
|
|
/** |
400 |
|
|
* Element returned by the most recent call to next iff that |
401 |
|
|
* element was drawn from the forgetMeNot list. |
402 |
|
|
*/ |
403 |
|
|
private Object lastRetElt = null; |
404 |
dl |
1.35 |
|
405 |
dl |
1.7 |
public boolean hasNext() { |
406 |
dl |
1.36 |
return cursor <= size || forgetMeNot != null; |
407 |
dl |
1.7 |
} |
408 |
|
|
|
409 |
|
|
public E next() { |
410 |
tim |
1.2 |
checkForComodification(); |
411 |
dl |
1.36 |
E result; |
412 |
|
|
if (cursor <= size) { |
413 |
|
|
result = (E) queue[cursor]; |
414 |
|
|
lastRet = cursor++; |
415 |
|
|
} |
416 |
|
|
else if (forgetMeNot == null) |
417 |
dl |
1.7 |
throw new NoSuchElementException(); |
418 |
dl |
1.36 |
else { |
419 |
|
|
int remaining = forgetMeNot.size(); |
420 |
|
|
result = forgetMeNot.remove(remaining - 1); |
421 |
|
|
if (remaining == 1) |
422 |
|
|
forgetMeNot = null; |
423 |
|
|
lastRet = 0; |
424 |
|
|
lastRetElt = result; |
425 |
|
|
} |
426 |
tim |
1.2 |
return result; |
427 |
dl |
1.7 |
} |
428 |
tim |
1.2 |
|
429 |
dl |
1.7 |
public void remove() { |
430 |
tim |
1.2 |
checkForComodification(); |
431 |
|
|
|
432 |
dl |
1.36 |
if (lastRet != 0) { |
433 |
|
|
E moved = PriorityQueue.this.removeAt(lastRet); |
434 |
|
|
lastRet = 0; |
435 |
|
|
if (moved == null) { |
436 |
|
|
cursor--; |
437 |
|
|
} else { |
438 |
|
|
if (forgetMeNot == null) |
439 |
dl |
1.37 |
forgetMeNot = new ArrayList<E>(); |
440 |
dl |
1.36 |
forgetMeNot.add(moved); |
441 |
|
|
} |
442 |
|
|
} else if (lastRetElt != null) { |
443 |
|
|
PriorityQueue.this.remove(lastRetElt); |
444 |
|
|
lastRetElt = null; |
445 |
|
|
} else { |
446 |
|
|
throw new IllegalStateException(); |
447 |
dl |
1.35 |
} |
448 |
|
|
|
449 |
tim |
1.2 |
expectedModCount = modCount; |
450 |
dl |
1.7 |
} |
451 |
tim |
1.2 |
|
452 |
dl |
1.7 |
final void checkForComodification() { |
453 |
|
|
if (modCount != expectedModCount) |
454 |
|
|
throw new ConcurrentModificationException(); |
455 |
|
|
} |
456 |
tim |
1.2 |
} |
457 |
|
|
|
458 |
tim |
1.1 |
public int size() { |
459 |
tim |
1.2 |
return size; |
460 |
tim |
1.1 |
} |
461 |
tim |
1.2 |
|
462 |
|
|
/** |
463 |
dl |
1.49 |
* Removes all elements from the priority queue. |
464 |
|
|
* The queue will be empty after this call returns. |
465 |
tim |
1.2 |
*/ |
466 |
|
|
public void clear() { |
467 |
|
|
modCount++; |
468 |
|
|
|
469 |
|
|
// Null out element references to prevent memory leak |
470 |
|
|
for (int i=1; i<=size; i++) |
471 |
|
|
queue[i] = null; |
472 |
|
|
|
473 |
|
|
size = 0; |
474 |
|
|
} |
475 |
|
|
|
476 |
dl |
1.40 |
public E poll() { |
477 |
dl |
1.36 |
if (size == 0) |
478 |
dl |
1.40 |
return null; |
479 |
dl |
1.36 |
modCount++; |
480 |
|
|
|
481 |
|
|
E result = (E) queue[1]; |
482 |
|
|
queue[1] = queue[size]; |
483 |
|
|
queue[size--] = null; // Drop extra ref to prevent memory leak |
484 |
|
|
if (size > 1) |
485 |
|
|
fixDown(1); |
486 |
|
|
|
487 |
|
|
return result; |
488 |
|
|
} |
489 |
|
|
|
490 |
|
|
/** |
491 |
|
|
* Removes and returns the ith element from queue. (Recall that queue |
492 |
|
|
* is one-based, so 1 <= i <= size.) |
493 |
tim |
1.2 |
* |
494 |
dl |
1.36 |
* Normally this method leaves the elements at positions from 1 up to i-1, |
495 |
|
|
* inclusive, untouched. Under these circumstances, it returns null. |
496 |
|
|
* Occasionally, in order to maintain the heap invariant, it must move |
497 |
|
|
* the last element of the list to some index in the range [2, i-1], |
498 |
|
|
* and move the element previously at position (i/2) to position i. |
499 |
|
|
* Under these circumstances, this method returns the element that was |
500 |
|
|
* previously at the end of the list and is now at some position between |
501 |
|
|
* 2 and i-1 inclusive. |
502 |
tim |
1.2 |
*/ |
503 |
dl |
1.36 |
private E removeAt(int i) { |
504 |
|
|
assert i > 0 && i <= size; |
505 |
tim |
1.2 |
modCount++; |
506 |
|
|
|
507 |
dl |
1.36 |
E moved = (E) queue[size]; |
508 |
|
|
queue[i] = moved; |
509 |
tim |
1.2 |
queue[size--] = null; // Drop extra ref to prevent memory leak |
510 |
dl |
1.35 |
if (i <= size) { |
511 |
tim |
1.2 |
fixDown(i); |
512 |
dl |
1.36 |
if (queue[i] == moved) { |
513 |
|
|
fixUp(i); |
514 |
|
|
if (queue[i] != moved) |
515 |
|
|
return moved; |
516 |
|
|
} |
517 |
dl |
1.35 |
} |
518 |
dl |
1.36 |
return null; |
519 |
tim |
1.1 |
} |
520 |
|
|
|
521 |
tim |
1.2 |
/** |
522 |
|
|
* Establishes the heap invariant (described above) assuming the heap |
523 |
|
|
* satisfies the invariant except possibly for the leaf-node indexed by k |
524 |
|
|
* (which may have a nextExecutionTime less than its parent's). |
525 |
|
|
* |
526 |
|
|
* This method functions by "promoting" queue[k] up the hierarchy |
527 |
|
|
* (by swapping it with its parent) repeatedly until queue[k] |
528 |
|
|
* is greater than or equal to its parent. |
529 |
|
|
*/ |
530 |
|
|
private void fixUp(int k) { |
531 |
|
|
if (comparator == null) { |
532 |
|
|
while (k > 1) { |
533 |
|
|
int j = k >> 1; |
534 |
tim |
1.16 |
if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0) |
535 |
tim |
1.2 |
break; |
536 |
tim |
1.16 |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
537 |
tim |
1.2 |
k = j; |
538 |
|
|
} |
539 |
|
|
} else { |
540 |
|
|
while (k > 1) { |
541 |
dl |
1.35 |
int j = k >>> 1; |
542 |
tim |
1.16 |
if (comparator.compare((E)queue[j], (E)queue[k]) <= 0) |
543 |
tim |
1.2 |
break; |
544 |
tim |
1.16 |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
545 |
tim |
1.2 |
k = j; |
546 |
|
|
} |
547 |
|
|
} |
548 |
|
|
} |
549 |
|
|
|
550 |
|
|
/** |
551 |
|
|
* Establishes the heap invariant (described above) in the subtree |
552 |
|
|
* rooted at k, which is assumed to satisfy the heap invariant except |
553 |
|
|
* possibly for node k itself (which may be greater than its children). |
554 |
|
|
* |
555 |
|
|
* This method functions by "demoting" queue[k] down the hierarchy |
556 |
|
|
* (by swapping it with its smaller child) repeatedly until queue[k] |
557 |
|
|
* is less than or equal to its children. |
558 |
|
|
*/ |
559 |
|
|
private void fixDown(int k) { |
560 |
|
|
int j; |
561 |
|
|
if (comparator == null) { |
562 |
dl |
1.33 |
while ((j = k << 1) <= size && (j > 0)) { |
563 |
dl |
1.35 |
if (j<size && |
564 |
|
|
((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0) |
565 |
tim |
1.2 |
j++; // j indexes smallest kid |
566 |
dl |
1.35 |
|
567 |
tim |
1.16 |
if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0) |
568 |
tim |
1.2 |
break; |
569 |
tim |
1.16 |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
570 |
tim |
1.2 |
k = j; |
571 |
|
|
} |
572 |
|
|
} else { |
573 |
dl |
1.33 |
while ((j = k << 1) <= size && (j > 0)) { |
574 |
dl |
1.35 |
if (j<size && |
575 |
|
|
comparator.compare((E)queue[j], (E)queue[j+1]) > 0) |
576 |
tim |
1.2 |
j++; // j indexes smallest kid |
577 |
tim |
1.16 |
if (comparator.compare((E)queue[k], (E)queue[j]) <= 0) |
578 |
tim |
1.2 |
break; |
579 |
tim |
1.16 |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
580 |
tim |
1.2 |
k = j; |
581 |
|
|
} |
582 |
|
|
} |
583 |
dl |
1.36 |
} |
584 |
dl |
1.35 |
|
585 |
dl |
1.36 |
/** |
586 |
|
|
* Establishes the heap invariant (described above) in the entire tree, |
587 |
|
|
* assuming nothing about the order of the elements prior to the call. |
588 |
|
|
*/ |
589 |
|
|
private void heapify() { |
590 |
|
|
for (int i = size/2; i >= 1; i--) |
591 |
|
|
fixDown(i); |
592 |
tim |
1.2 |
} |
593 |
|
|
|
594 |
dholmes |
1.23 |
/** |
595 |
|
|
* Returns the comparator used to order this collection, or <tt>null</tt> |
596 |
|
|
* if this collection is sorted according to its elements natural ordering |
597 |
tim |
1.24 |
* (using <tt>Comparable</tt>). |
598 |
dholmes |
1.23 |
* |
599 |
|
|
* @return the comparator used to order this collection, or <tt>null</tt> |
600 |
|
|
* if this collection is sorted according to its elements natural ordering. |
601 |
|
|
*/ |
602 |
tim |
1.16 |
public Comparator<? super E> comparator() { |
603 |
tim |
1.2 |
return comparator; |
604 |
|
|
} |
605 |
dl |
1.5 |
|
606 |
|
|
/** |
607 |
|
|
* Save the state of the instance to a stream (that |
608 |
|
|
* is, serialize it). |
609 |
|
|
* |
610 |
|
|
* @serialData The length of the array backing the instance is |
611 |
|
|
* emitted (int), followed by all of its elements (each an |
612 |
|
|
* <tt>Object</tt>) in the proper order. |
613 |
dl |
1.7 |
* @param s the stream |
614 |
dl |
1.5 |
*/ |
615 |
dl |
1.22 |
private void writeObject(java.io.ObjectOutputStream s) |
616 |
dl |
1.5 |
throws java.io.IOException{ |
617 |
dl |
1.7 |
// Write out element count, and any hidden stuff |
618 |
|
|
s.defaultWriteObject(); |
619 |
dl |
1.5 |
|
620 |
|
|
// Write out array length |
621 |
|
|
s.writeInt(queue.length); |
622 |
|
|
|
623 |
dl |
1.7 |
// Write out all elements in the proper order. |
624 |
dl |
1.39 |
for (int i=1; i<=size; i++) |
625 |
dl |
1.5 |
s.writeObject(queue[i]); |
626 |
|
|
} |
627 |
|
|
|
628 |
|
|
/** |
629 |
|
|
* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is, |
630 |
|
|
* deserialize it). |
631 |
dl |
1.7 |
* @param s the stream |
632 |
dl |
1.5 |
*/ |
633 |
dl |
1.22 |
private void readObject(java.io.ObjectInputStream s) |
634 |
dl |
1.5 |
throws java.io.IOException, ClassNotFoundException { |
635 |
dl |
1.7 |
// Read in size, and any hidden stuff |
636 |
|
|
s.defaultReadObject(); |
637 |
dl |
1.5 |
|
638 |
|
|
// Read in array length and allocate array |
639 |
|
|
int arrayLength = s.readInt(); |
640 |
tim |
1.16 |
queue = new Object[arrayLength]; |
641 |
dl |
1.5 |
|
642 |
dl |
1.7 |
// Read in all elements in the proper order. |
643 |
dl |
1.39 |
for (int i=1; i<=size; i++) |
644 |
dl |
1.37 |
queue[i] = (E) s.readObject(); |
645 |
dl |
1.5 |
} |
646 |
|
|
|
647 |
tim |
1.1 |
} |