SoftSet.java Source code

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Here is the source code for SoftSet.java

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/*
 * JBoss, Home of Professional Open Source
 * Copyright 2005, JBoss Inc., and individual contributors as indicated
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.lang.reflect.Array;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;

/**
 * An implementation of Set that manages a map of soft references to the set
 * values. The map is keyed by the value hashCode and so this is only useful for
 * value whose hashCode is a valid identity representation (String, primative
 * wrappers, etc).
 * 
 * @author Scott.Stark@jboss.org
 * @version $Revision: 2787 $
 */
@SuppressWarnings("unchecked")
public class SoftSet implements Set {
    private HashMap map = new HashMap();

    /** The queue of garbage collected soft references */
    private ReferenceQueue gcqueue = new ReferenceQueue();

    static class ComparableSoftReference extends SoftReference {
        private Integer key;

        ComparableSoftReference(Integer key, Object o, ReferenceQueue q) {
            super(o, q);
            this.key = key;
        }

        Integer getKey() {
            return key;
        }
    }

    static class ComparableSoftReferenceIterator implements Iterator {
        Iterator theIter;

        ComparableSoftReferenceIterator(Iterator theIter) {
            this.theIter = theIter;
        }

        public boolean hasNext() {
            return theIter.hasNext();
        }

        public Object next() {
            ComparableSoftReference csr = (ComparableSoftReference) theIter.next();
            return csr.get();
        }

        public void remove() {
            theIter.remove();
        }
    }

    /**
     * 
     */
    public SoftSet() {
    }

    public int size() {
        processQueue();
        return map.size();
    }

    public boolean isEmpty() {
        processQueue();
        return map.isEmpty();
    }

    public boolean contains(Object o) {
        processQueue();
        Integer key = new Integer(o.hashCode());
        boolean contains = map.containsKey(key);
        return contains;
    }

    public Iterator iterator() {
        processQueue();
        Iterator theIter = map.values().iterator();
        return new ComparableSoftReferenceIterator(theIter);
    }

    public Object[] toArray() {
        processQueue();
        return toArray(new Object[0]);
    }

    public Object[] toArray(Object[] a) {
        processQueue();
        int size = map.size();
        Object[] array = {};
        if (a.length >= size)
            array = a;
        Iterator iter = map.values().iterator();
        int index = 0;
        while (iter.hasNext()) {
            ComparableSoftReference csr = (ComparableSoftReference) iter.next();
            Object value = csr.get();
            // Create the correct array type
            if (array.length == 0) {
                if (value == null) {
                    index++;
                    continue;
                }
                Array.newInstance(value.getClass(), size);
            }
            array[index] = value;
            index++;
        }
        return array;
    }

    public boolean add(Object o) {
        processQueue();
        Integer key = new Integer(o.hashCode());
        ComparableSoftReference sr = new ComparableSoftReference(key, o, gcqueue);
        return map.put(key, sr) == null;
    }

    public boolean remove(Object o) {
        processQueue();
        Integer key = new Integer(o.hashCode());
        return map.remove(key) != null;
    }

    public boolean containsAll(Collection c) {
        processQueue();
        Iterator iter = c.iterator();
        boolean contains = true;
        while (iter.hasNext()) {
            Object value = iter.next();
            Integer key = new Integer(value.hashCode());
            contains &= map.containsKey(key);
        }
        return contains;
    }

    public boolean addAll(Collection c) {
        processQueue();
        Iterator iter = c.iterator();
        boolean added = false;
        while (iter.hasNext()) {
            Object value = iter.next();
            Integer key = new Integer(value.hashCode());
            ComparableSoftReference sr = new ComparableSoftReference(key, value, gcqueue);
            added |= map.put(key, sr) == null;
        }
        return added;
    }

    public boolean retainAll(Collection c) {
        Iterator iter = iterator();
        boolean removed = false;
        while (iter.hasNext()) {
            Object value = iter.next();
            if (c.contains(value) == false) {
                iter.remove();
                removed = true;
            }
        }
        return removed;
    }

    public boolean removeAll(Collection c) {
        processQueue();
        Iterator iter = c.iterator();
        boolean removed = false;
        while (iter.hasNext()) {
            Object value = iter.next();
            removed |= remove(value);
        }
        return removed;
    }

    public void clear() {
        while (gcqueue.poll() != null)
            ;
        map.clear();
    }

    public boolean equals(Object o) {
        return map.equals(o);
    }

    public int hashCode() {
        return map.hashCode();
    }

    /**
     * Iterate through the gcqueue for for any cleared reference, remove the
     * associated value from the underlying set.
     */
    private void processQueue() {
        ComparableSoftReference cr;
        while ((cr = (ComparableSoftReference) gcqueue.poll()) != null) {
            map.remove(cr.getKey());
        }
    }

}