Merged gcj-eclipse branch to trunk.
From-SVN: r120621
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Tom Tromey
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97b8365caf
17478 changed files with 606493 additions and 100744 deletions
335
libjava/classpath/java/util/PriorityQueue.java
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335
libjava/classpath/java/util/PriorityQueue.java
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/* PriorityQueue.java -- Unbounded priority queue
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Copyright (C) 2004, 2005 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.util;
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import java.io.Serializable;
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/**
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* @author Tom Tromey (tromey@redhat.com)
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* @author Andrew John Hughes (gnu_andrew@member.fsf.org)
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* @since 1.5
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*/
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public class PriorityQueue<E> extends AbstractQueue<E> implements Serializable
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{
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private static final int DEFAULT_CAPACITY = 11;
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private static final long serialVersionUID = -7720805057305804111L;
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/** Number of elements actually used in the storage array. */
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int used;
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/**
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* This is the storage for the underlying binomial heap.
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* The idea is, each node is less than or equal to its children.
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* A node at index N (0-based) has two direct children, at
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* nodes 2N+1 and 2N+2.
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*/
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E[] storage;
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/**
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* The comparator we're using, or null for natural ordering.
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*/
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Comparator<? super E> comparator;
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public PriorityQueue()
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{
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this(DEFAULT_CAPACITY, null);
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}
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public PriorityQueue(Collection<? extends E> c)
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{
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this(Math.max(1, (int) (1.1 * c.size())), null);
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// Special case where we can find the comparator to use.
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if (c instanceof SortedSet)
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{
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SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
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this.comparator = (Comparator<? super E>) ss.comparator();
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// We can insert the elements directly, since they are sorted.
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int i = 0;
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for (E val : ss)
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{
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if (val == null)
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throw new NullPointerException();
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storage[i++] = val;
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}
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}
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else if (c instanceof PriorityQueue)
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{
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PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
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this.comparator = (Comparator<? super E>)pq.comparator();
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// We can just copy the contents.
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System.arraycopy(pq.storage, 0, storage, 0, pq.storage.length);
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}
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addAll(c);
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}
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public PriorityQueue(int cap)
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{
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this(cap, null);
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}
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public PriorityQueue(int cap, Comparator<? super E> comp)
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{
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if (cap < 1)
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throw new IllegalArgumentException();
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this.used = 0;
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this.storage = (E[]) new Object[cap];
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this.comparator = comp;
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}
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public PriorityQueue(PriorityQueue<? extends E> c)
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{
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this(Math.max(1, (int) (1.1 * c.size())),
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(Comparator<? super E>)c.comparator());
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// We can just copy the contents.
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System.arraycopy(c.storage, 0, storage, 0, c.storage.length);
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}
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public PriorityQueue(SortedSet<? extends E> c)
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{
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this(Math.max(1, (int) (1.1 * c.size())),
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(Comparator<? super E>)c.comparator());
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// We can insert the elements directly, since they are sorted.
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int i = 0;
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for (E val : c)
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{
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if (val == null)
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throw new NullPointerException();
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storage[i++] = val;
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}
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}
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public void clear()
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{
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Arrays.fill(storage, null);
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used = 0;
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}
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public Comparator<? super E> comparator()
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{
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return comparator;
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}
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public Iterator<E> iterator()
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{
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return new Iterator<E>()
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{
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int index = -1;
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int count = 0;
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public boolean hasNext()
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{
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return count < used;
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}
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public E next()
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{
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while (storage[++index] == null)
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;
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++count;
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return storage[index];
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}
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public void remove()
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{
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PriorityQueue.this.remove(index);
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index--;
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}
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};
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}
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public boolean offer(E o)
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{
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if (o == null)
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throw new NullPointerException();
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int slot = findSlot(-1);
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storage[slot] = o;
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++used;
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bubbleUp(slot);
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return true;
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}
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public E peek()
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{
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return used == 0 ? null : storage[0];
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}
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public E poll()
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{
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if (used == 0)
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return null;
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E result = storage[0];
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remove(0);
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return result;
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}
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public boolean remove(Object o)
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{
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if (o != null)
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{
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for (int i = 0; i < storage.length; ++i)
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{
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if (o.equals(storage[i]))
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{
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remove(i);
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return true;
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}
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}
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}
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return false;
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}
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public int size()
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{
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return used;
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}
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// It is more efficient to implement this locally -- less searching
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// for free slots.
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public boolean addAll(Collection<? extends E> c)
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{
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if (c == this)
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throw new IllegalArgumentException();
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int newSlot = -1;
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int save = used;
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for (E val : c)
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{
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if (val == null)
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throw new NullPointerException();
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newSlot = findSlot(newSlot);
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storage[newSlot] = val;
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++used;
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bubbleUp(newSlot);
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}
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return save != used;
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}
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int findSlot(int start)
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{
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int slot;
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if (used == storage.length)
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{
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resize();
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slot = used;
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}
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else
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{
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for (slot = start + 1; slot < storage.length; ++slot)
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{
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if (storage[slot] == null)
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break;
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}
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// We'll always find a slot.
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}
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return slot;
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}
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void remove(int index)
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{
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// Remove the element at INDEX. We do this by finding the least
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// child and moving it into place, then iterating until we reach
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// the bottom of the tree.
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while (storage[index] != null)
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{
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int child = 2 * index + 1;
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// See if we went off the end.
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if (child >= storage.length)
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{
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storage[index] = null;
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break;
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}
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// Find which child we want to promote. If one is not null,
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// we pick it. If both are null, it doesn't matter, we're
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// about to leave. If neither is null, pick the lesser.
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if (child + 1 >= storage.length || storage[child + 1] == null)
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{
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// Nothing.
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}
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else if (storage[child] == null
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|| (Collections.compare(storage[child], storage[child + 1],
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comparator) > 0))
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++child;
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storage[index] = storage[child];
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index = child;
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}
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--used;
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}
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void bubbleUp(int index)
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{
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// The element at INDEX was inserted into a blank spot. Now move
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// it up the tree to its natural resting place.
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while (index > 0)
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{
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// This works regardless of whether we're at 2N+1 or 2N+2.
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int parent = (index - 1) / 2;
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if (Collections.compare(storage[parent], storage[index], comparator)
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<= 0)
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{
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// Parent is the same or smaller than this element, so the
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// invariant is preserved. Note that if the new element
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// is smaller than the parent, then it is necessarily
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// smaller than the parent's other child.
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break;
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}
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E temp = storage[index];
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storage[index] = storage[parent];
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storage[parent] = temp;
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index = parent;
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}
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}
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void resize()
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{
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E[] new_data = (E[]) new Object[2 * storage.length];
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System.arraycopy(storage, 0, new_data, 0, storage.length);
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storage = new_data;
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}
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}
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