/*
 *                 Sun Public License Notice
 * 
 * The contents of this file are subject to the Sun Public License
 * Version 1.0 (the "License"). You may not use this file except in
 * compliance with the License. A copy of the License is available at
 * http://www.sun.com/
 * 
 * The Original Code is NetBeans. The Initial Developer of the Original
 * Code is Sun Microsystems, Inc. Portions Copyright 1997-2001 Sun
 * Microsystems, Inc. All Rights Reserved.
 */

package org.netbeans.modules.vcscore.util;

import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.AbstractList;
import java.util.Collection;
import java.util.Iterator;

/**
 * A simple list wich holds only weak references to the original objects.
 * @author  Martin Entlicher
 */
public class WeakList extends AbstractList {
    
    private ArrayList items;

    /** Creates new WeakList */
    public WeakList() {
        items = new ArrayList();
    }
    
    public WeakList(Collection c) {
        items = new ArrayList();
        addAll(0, c);
    }
    
    public void add(int index, Object element) {
        items.add(index, new WeakReference(element));
    }
    
    public Iterator iterator() {
        return new WeakListIterator();
    }
    
    public int size() {
        removeReleased();
        return items.size();
    }    
    
    public java.lang.Object get(int index) {
        return ((WeakReference) items.get(index)).get();
    }
    
    private void removeReleased() {
        for (Iterator it = items.iterator(); it.hasNext(); ) {
            WeakReference ref = (WeakReference) it.next();
            if (ref.get() == null) items.remove(ref);
        }
    }
    
    private class WeakListIterator implements Iterator {
        
        private int n;
        private int i;
        
        public WeakListIterator() {
            n = size();
            i = 0;
        }
        
        public boolean hasNext() {
            return i < n;
        }
        
        public Object next() {
            return get(i++);
        }
        
        public void remove() {
            throw new UnsupportedOperationException();
        }
        
    }

}