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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}: |
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* 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 <em>head</em> of this queue is the least element with respect to the |
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* specified ordering. If multiple elements are tied for least value, the |
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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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* |
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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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* @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>, 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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* 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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* 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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* The number of times this priority queue has been |
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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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throw new IllegalArgumentException(); |
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queue = (E[]) new Object[initialCapacity + 1]; |
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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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* 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; or 1 if the collection is empty. |
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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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* @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> c) { |
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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 = (E[]) new Object[initialCapacity + 1]; |
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this.queue = new Object[initialCapacity + 1]; |
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// FIXME: if c is larger than Integer.MAX_VALUE we'll |
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// overflow the array |
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if (c instanceof Sorted) { |
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// FIXME: this code assumes too much |
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comparator = ((Sorted)c).comparator(); |
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for (Iterator<E> i = c.iterator(); i.hasNext(); ) |
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queue[++size] = i.next(); |
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} else { |
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comparator = null; |
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for (Iterator<E> i = c.iterator(); i.hasNext(); ) |
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add(i.next()); |
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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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* Add the specified element to this priority queue. |
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* |
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* @param element the element to add. |
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* @return <tt>true</tt> |
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* @throws ClassCastException if the specified element cannot be compared |
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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 null. |
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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 element) { |
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if (element == null) |
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public boolean offer(E o) { |
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if (o == null) |
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throw new NullPointerException(); |
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modCount++; |
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++size; |
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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? |
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while (size >= queue.length) { |
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E[] newQueue = (E[]) new Object[2 * 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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queue[size] = element; |
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queue[size] = o; |
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fixUp(size); |
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return true; |
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} |
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public E poll() { |
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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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public E peek() { |
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return queue[1]; |
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return (E) queue[1]; |
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} |
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// Collection Methods |
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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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*/ |
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public boolean add(E element) { |
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return super.add(element); |
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public boolean add(E o) { |
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return super.add(o); |
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} |
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/** |
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* @throws NullPointerException if any element is <tt>null</tt>. |
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* @throws ClassCastException if any element cannot be compared |
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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 <tt>c</tt> or any element in <tt>c</tt> |
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* is <tt>null</tt> |
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*/ |
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public boolean addAll(Collection<? extends E> c) { |
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return super.addAll(c); |
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if (comparator == null) { |
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for (int i = 1; i <= size; i++) { |
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if (((Comparable)queue[i]).compareTo(o) == 0) { |
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if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) { |
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remove(i); |
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return true; |
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} |
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} |
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} else { |
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for (int i = 1; i <= size; i++) { |
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if (comparator.compare(queue[i], (E)o) == 0) { |
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if (comparator.compare((E)queue[i], (E)o) == 0) { |
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remove(i); |
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return true; |
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} |
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checkForComodification(); |
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if (cursor > size) |
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throw new NoSuchElementException(); |
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E result = queue[cursor]; |
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E result = (E) queue[cursor]; |
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lastRet = cursor++; |
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return result; |
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} |
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assert i <= size; |
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modCount++; |
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E result = queue[i]; |
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E result = (E) queue[i]; |
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queue[i] = queue[size]; |
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queue[size--] = null; // Drop extra ref to prevent memory leak |
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if (i <= size) |
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if (comparator == null) { |
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while (k > 1) { |
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int j = k >> 1; |
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if (((Comparable)queue[j]).compareTo(queue[k]) <= 0) |
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if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0) |
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break; |
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E tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
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Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
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k = j; |
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} |
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} else { |
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while (k > 1) { |
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int j = k >> 1; |
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if (comparator.compare(queue[j], queue[k]) <= 0) |
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if (comparator.compare((E)queue[j], (E)queue[k]) <= 0) |
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break; |
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E tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
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Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
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k = j; |
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} |
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} |
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int j; |
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if (comparator == null) { |
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while ((j = k << 1) <= size) { |
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if (j<size && ((Comparable)queue[j]).compareTo(queue[j+1]) > 0) |
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if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0) |
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j++; // j indexes smallest kid |
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if (((Comparable)queue[k]).compareTo(queue[j]) <= 0) |
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if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0) |
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break; |
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E tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
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Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
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k = j; |
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} |
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} else { |
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while ((j = k << 1) <= size) { |
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if (j < size && comparator.compare(queue[j], queue[j+1]) > 0) |
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if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0) |
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j++; // j indexes smallest kid |
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if (comparator.compare(queue[k], queue[j]) <= 0) |
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if (comparator.compare((E)queue[k], (E)queue[j]) <= 0) |
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break; |
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E tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
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Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
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k = j; |
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} |
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} |
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} |
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public Comparator comparator() { |
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public Comparator<? super E> comparator() { |
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return comparator; |
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} |
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// Read in array length and allocate array |
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int arrayLength = s.readInt(); |
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queue = (E[]) new Object[arrayLength]; |
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queue = new Object[arrayLength]; |
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// Read in all elements in the proper order. |
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for (int i=0; i<size; i++) |
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queue[i] = (E)s.readObject(); |
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queue[i] = s.readObject(); |
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} |
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} |