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package java.util; |
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/** |
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* An unbounded priority queue based on a priority heap. This queue orders |
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* A priority queue based on a priority heap. This queue orders |
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* elements according to an order specified at construction time, which is |
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* specified in the same manner as {@link TreeSet} and {@link TreeMap}: elements are ordered |
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* specified in the same manner as {@link java.util.TreeSet} and |
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* {@link java.util.TreeMap}: elements are ordered |
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* either according to their <i>natural order</i> (see {@link Comparable}), or |
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* according to a {@link Comparator}, depending on which constructor is used. |
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* The {@link #peek}, {@link #poll}, and {@link #remove} methods return the |
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* minimal element with respect to the specified ordering. If multiple |
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* elements are tied for least value, no guarantees are made as to |
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* which of these elements is returned. |
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* according to a {@link java.util.Comparator}, depending on which |
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* constructor is used. |
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* <p>The <em>head</em> of this queue is the <em>least</em> element with |
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* respect to the specified ordering. |
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* If multiple elements are tied for least value, the |
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* head is one of those elements. A priority queue does not permit |
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* <tt>null</tt> elements. |
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* |
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* <p>The {@link #remove()} and {@link #poll()} methods remove and |
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* return the head of the queue. |
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* |
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* <p>The {@link #element()} and {@link #peek()} methods return, but do |
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* not delete, the head of the queue. |
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* |
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* <p>A priority queue has a <i>capacity</i>. The capacity is the |
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* size of the array used internally to store the elements on the |
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* queue. It is always at least as large as the queue size. As |
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* queue, and is limited to <tt>Integer.MAX_VALUE-1</tt>. |
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* It is always at least as large as the queue size. As |
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* elements are added to a priority queue, its capacity grows |
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* automatically. The details of the growth policy are not specified. |
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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 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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* @author Josh Bloch |
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*/ |
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public class PriorityQueue<E> extends AbstractQueue<E> |
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implements Queue<E>, |
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java.io.Serializable { |
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implements Sorted, Queue<E>, java.io.Serializable { |
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private static final int DEFAULT_INITIAL_CAPACITY = 11; |
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/** |
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* |
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* queue.length must be >= 2, even if size == 0. |
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*/ |
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private transient E[] queue; |
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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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* 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<E> comparator; |
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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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private transient int modCount = 0; |
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/** |
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* Create a new priority queue with the default initial capacity |
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* Create a <tt>PriorityQueue</tt> with the default initial capacity |
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* (11) that orders its elements according to their natural |
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* ordering (using <tt>Comparable</tt>.) |
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*/ |
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public PriorityQueue() { |
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this(DEFAULT_INITIAL_CAPACITY); |
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this(DEFAULT_INITIAL_CAPACITY, null); |
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} |
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/** |
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* Create a new priority queue with the specified initial capacity |
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* Create a <tt>PriorityQueue</tt> with the specified initial capacity |
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* that orders its elements according to their natural ordering |
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* (using <tt>Comparable</tt>.) |
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* |
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} |
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/** |
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* Create a new priority queue with the specified initial capacity (11) |
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* Create 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 used to order this priority queue. |
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* If <tt>null</tt> then the order depends on the elements' natural |
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* ordering. |
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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, Comparator<E> comparator) { |
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public PriorityQueue(int initialCapacity, Comparator<? super E> comparator) { |
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if (initialCapacity < 1) |
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initialCapacity = 1; |
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queue = new E[initialCapacity + 1]; |
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throw new IllegalArgumentException(); |
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this.queue = new Object[initialCapacity + 1]; |
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this.comparator = comparator; |
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} |
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|
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/** |
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* Create a new priority queue containing the elements in the specified |
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* Create a <tt>PriorityQueue</tt> containing the elements in the specified |
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* collection. The priority queue has an initial capacity of 110% of the |
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* size of the specified collection. If the specified collection |
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* size of the specified collection (bounded by |
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* <tt>Integer.MAX_VALUE-1</tt>); or 1 if the collection is empty. |
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* If the specified collection |
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* implements the {@link Sorted} interface, the priority queue will be |
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* sorted according to the same comparator, or according to its elements' |
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* natural order if the collection is sorted according to its elements' |
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* <tt>Sorted</tt>, the priority queue is ordered according to |
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* its elements' natural order. |
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* |
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* @param initialElements the collection whose elements are to be placed |
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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 an |
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* element of the specified collection is <tt>null</tt>. |
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* @throws NullPointerException if <tt>c</tt> or any element within it |
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* is <tt>null</tt> |
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*/ |
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public PriorityQueue(Collection<E> initialElements) { |
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int sz = initialElements.size(); |
139 |
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public PriorityQueue(Collection<? extends E> c) { |
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int sz = c.size(); |
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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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queue = new E[initialCapacity + 1]; |
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|
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this.queue = new Object[initialCapacity + 1]; |
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|
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if (initialElements instanceof Sorted) { |
149 |
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comparator = ((Sorted)initialElements).comparator(); |
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for (Iterator<E> i = initialElements.iterator(); i.hasNext(); ) |
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queue[++size] = i.next(); |
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// FIXME: if c is larger than Integer.MAX_VALUE we'll |
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// overflow the array |
150 |
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|
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if (c instanceof Sorted) { |
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comparator = ((Sorted)c).comparator(); |
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} else { |
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comparator = null; |
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for (Iterator<E> i = initialElements.iterator(); i.hasNext(); ) |
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add(i.next()); |
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} |
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|
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for (Iterator<? extends E> i = c.iterator(); i.hasNext(); ) |
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add(i.next()); |
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} |
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// Queue Methods |
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/** |
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* Remove and return the minimal element from this priority queue |
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* if it contains one or more elements, otherwise return |
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* <tt>null</tt>. The term <i>minimal</i> is defined according to |
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* this priority queue's order. |
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* Add the specified element to this priority queue. |
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* |
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* @return the minimal element from this priority queue if it contains |
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* one or more elements, otherwise <tt>null</tt>. |
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* @return <tt>true</tt> |
167 |
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* @throws ClassCastException if the specified element cannot be compared |
168 |
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* with elements currently in the priority queue according |
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* to the priority queue's ordering. |
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* @throws NullPointerException if the specified element is <tt>null</tt>. |
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*/ |
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public boolean offer(E o) { |
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if (o == null) |
174 |
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throw new NullPointerException(); |
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modCount++; |
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++size; |
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|
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// Grow backing store if necessary |
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// FIXME: watch for overflow |
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// FIXME: what if we're full? |
181 |
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while (size >= queue.length) { |
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Object[] newQueue = new Object[2 * queue.length]; |
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System.arraycopy(queue, 0, newQueue, 0, queue.length); |
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queue = newQueue; |
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} |
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|
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queue[size] = o; |
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fixUp(size); |
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return true; |
190 |
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} |
191 |
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|
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public E poll() { |
193 |
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if (size == 0) |
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return null; |
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return remove(1); |
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> |
return (E) remove(1); |
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} |
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|
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/** |
161 |
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* Return, but do not remove, the minimal element from the |
162 |
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* priority queue, or return <tt>null</tt> if the queue is empty. |
163 |
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* The term <i>minimal</i> is defined according to this priority |
164 |
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* queue's order. This method returns the same object reference |
165 |
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* that would be returned by by the <tt>poll</tt> method. The two |
166 |
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* methods differ in that this method does not remove the element |
167 |
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* from the priority queue. |
168 |
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* |
169 |
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* @return the minimal element from this priority queue if it contains |
170 |
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* one or more elements, otherwise <tt>null</tt>. |
171 |
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*/ |
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public E peek() { |
199 |
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return queue[1]; |
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> |
return (E) queue[1]; |
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} |
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|
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// Collection Methods |
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|
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// these first two override just to get the throws docs |
205 |
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|
206 |
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/** |
207 |
< |
* Removes a single instance of the specified element from this priority |
180 |
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* queue, if it is present. Returns true if this collection contained the |
181 |
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* specified element (or equivalently, if this collection changed as a |
182 |
< |
* result of the call). |
183 |
< |
* |
184 |
< |
* @param element the element to be removed from this collection, |
185 |
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* if present. |
186 |
< |
* @return <tt>true</tt> if this collection changed as a result of the |
187 |
< |
* call |
207 |
> |
* @throws NullPointerException if the specified element is <tt>null</tt>. |
208 |
|
* @throws ClassCastException if the specified element cannot be compared |
209 |
< |
* with elements currently in the priority queue according |
210 |
< |
* to the priority queue's ordering. |
191 |
< |
* @throws NullPointerException if the specified element is null. |
209 |
> |
* with elements currently in the priority queue according |
210 |
> |
* to the priority queue's ordering. |
211 |
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*/ |
212 |
< |
public boolean remove(Object element) { |
213 |
< |
if (element == null) |
214 |
< |
throw new NullPointerException(); |
212 |
> |
public boolean add(E o) { |
213 |
> |
return super.add(o); |
214 |
> |
} |
215 |
> |
|
216 |
> |
/** |
217 |
> |
* @throws ClassCastException if any element cannot be compared |
218 |
> |
* with elements currently in the priority queue according |
219 |
> |
* to the priority queue's ordering. |
220 |
> |
* @throws NullPointerException if <tt>c</tt> or any element in <tt>c</tt> |
221 |
> |
* is <tt>null</tt> |
222 |
> |
*/ |
223 |
> |
public boolean addAll(Collection<? extends E> c) { |
224 |
> |
return super.addAll(c); |
225 |
> |
} |
226 |
> |
|
227 |
> |
public boolean remove(Object o) { |
228 |
> |
if (o == null) |
229 |
> |
return false; |
230 |
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|
231 |
|
if (comparator == null) { |
232 |
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for (int i = 1; i <= size; i++) { |
233 |
< |
if (((Comparable)queue[i]).compareTo(element) == 0) { |
233 |
> |
if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) { |
234 |
|
remove(i); |
235 |
|
return true; |
236 |
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} |
237 |
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} |
238 |
|
} else { |
239 |
|
for (int i = 1; i <= size; i++) { |
240 |
< |
if (comparator.compare(queue[i], (E) element) == 0) { |
240 |
> |
if (comparator.compare((E)queue[i], (E)o) == 0) { |
241 |
|
remove(i); |
242 |
|
return true; |
243 |
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} |
246 |
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return false; |
247 |
|
} |
248 |
|
|
215 |
– |
/** |
216 |
– |
* Returns an iterator over the elements in this priority queue. The |
217 |
– |
* elements of the priority queue will be returned by this iterator in the |
218 |
– |
* order specified by the queue, which is to say the order they would be |
219 |
– |
* returned by repeated calls to <tt>poll</tt>. |
220 |
– |
* |
221 |
– |
* @return an <tt>Iterator</tt> over the elements in this priority queue. |
222 |
– |
*/ |
249 |
|
public Iterator<E> iterator() { |
250 |
|
return new Itr(); |
251 |
|
} |
279 |
|
checkForComodification(); |
280 |
|
if (cursor > size) |
281 |
|
throw new NoSuchElementException(); |
282 |
< |
E result = queue[cursor]; |
282 |
> |
E result = (E) queue[cursor]; |
283 |
|
lastRet = cursor++; |
284 |
|
return result; |
285 |
|
} |
304 |
|
|
305 |
|
/** |
306 |
|
* Returns the number of elements in this priority queue. |
307 |
< |
* |
307 |
> |
* |
308 |
|
* @return the number of elements in this priority queue. |
309 |
|
*/ |
310 |
|
public int size() { |
312 |
|
} |
313 |
|
|
314 |
|
/** |
289 |
– |
* Add the specified element to this priority queue. |
290 |
– |
* |
291 |
– |
* @param element the element to add. |
292 |
– |
* @return true |
293 |
– |
* @throws ClassCastException if the specified element cannot be compared |
294 |
– |
* with elements currently in the priority queue according |
295 |
– |
* to the priority queue's ordering. |
296 |
– |
* @throws NullPointerException if the specified element is null. |
297 |
– |
*/ |
298 |
– |
public boolean offer(E element) { |
299 |
– |
if (element == null) |
300 |
– |
throw new NullPointerException(); |
301 |
– |
modCount++; |
302 |
– |
++size; |
303 |
– |
|
304 |
– |
// Grow backing store if necessary |
305 |
– |
while (size >= queue.length) { |
306 |
– |
E[] newQueue = new E[2 * queue.length]; |
307 |
– |
System.arraycopy(queue, 0, newQueue, 0, queue.length); |
308 |
– |
queue = newQueue; |
309 |
– |
} |
310 |
– |
|
311 |
– |
queue[size] = element; |
312 |
– |
fixUp(size); |
313 |
– |
return true; |
314 |
– |
} |
315 |
– |
|
316 |
– |
/** |
315 |
|
* Remove all elements from the priority queue. |
316 |
|
*/ |
317 |
|
public void clear() { |
335 |
|
assert i <= size; |
336 |
|
modCount++; |
337 |
|
|
338 |
< |
E result = queue[i]; |
338 |
> |
E result = (E) queue[i]; |
339 |
|
queue[i] = queue[size]; |
340 |
|
queue[size--] = null; // Drop extra ref to prevent memory leak |
341 |
|
if (i <= size) |
356 |
|
if (comparator == null) { |
357 |
|
while (k > 1) { |
358 |
|
int j = k >> 1; |
359 |
< |
if (((Comparable)queue[j]).compareTo(queue[k]) <= 0) |
359 |
> |
if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0) |
360 |
|
break; |
361 |
< |
E tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
361 |
> |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
362 |
|
k = j; |
363 |
|
} |
364 |
|
} else { |
365 |
|
while (k > 1) { |
366 |
|
int j = k >> 1; |
367 |
< |
if (comparator.compare(queue[j], queue[k]) <= 0) |
367 |
> |
if (comparator.compare((E)queue[j], (E)queue[k]) <= 0) |
368 |
|
break; |
369 |
< |
E tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
369 |
> |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
370 |
|
k = j; |
371 |
|
} |
372 |
|
} |
385 |
|
int j; |
386 |
|
if (comparator == null) { |
387 |
|
while ((j = k << 1) <= size) { |
388 |
< |
if (j<size && ((Comparable)queue[j]).compareTo(queue[j+1]) > 0) |
388 |
> |
if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0) |
389 |
|
j++; // j indexes smallest kid |
390 |
< |
if (((Comparable)queue[k]).compareTo(queue[j]) <= 0) |
390 |
> |
if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0) |
391 |
|
break; |
392 |
< |
E tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
392 |
> |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
393 |
|
k = j; |
394 |
|
} |
395 |
|
} else { |
396 |
|
while ((j = k << 1) <= size) { |
397 |
< |
if (j < size && comparator.compare(queue[j], queue[j+1]) > 0) |
397 |
> |
if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0) |
398 |
|
j++; // j indexes smallest kid |
399 |
< |
if (comparator.compare(queue[k], queue[j]) <= 0) |
399 |
> |
if (comparator.compare((E)queue[k], (E)queue[j]) <= 0) |
400 |
|
break; |
401 |
< |
E tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
401 |
> |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
402 |
|
k = j; |
403 |
|
} |
404 |
|
} |
405 |
|
} |
406 |
|
|
407 |
< |
/** |
410 |
< |
* Returns the comparator associated with this priority queue, or |
411 |
< |
* <tt>null</tt> if it uses its elements' natural ordering. |
412 |
< |
* |
413 |
< |
* @return the comparator associated with this priority queue, or |
414 |
< |
* <tt>null</tt> if it uses its elements' natural ordering. |
415 |
< |
*/ |
416 |
< |
public Comparator comparator() { |
407 |
> |
public Comparator<? super E> comparator() { |
408 |
|
return comparator; |
409 |
|
} |
410 |
|
|
442 |
|
|
443 |
|
// Read in array length and allocate array |
444 |
|
int arrayLength = s.readInt(); |
445 |
< |
queue = new E[arrayLength]; |
445 |
> |
queue = new Object[arrayLength]; |
446 |
|
|
447 |
|
// Read in all elements in the proper order. |
448 |
|
for (int i=0; i<size; i++) |
449 |
< |
queue[i] = (E)s.readObject(); |
449 |
> |
queue[i] = s.readObject(); |
450 |
|
} |
451 |
|
|
452 |
|
} |
453 |
+ |
|