001    /*
002      Copyright (C) 2001 Laurent Martelli <laurent@aopsys.com>
003    
004      This program is free software; you can redistribute it and/or modify
005      it under the terms of the GNU Lesser General Public License as
006      published by the Free Software Foundation; either version 2 of the
007      License, or (at your option) any later version.
008    
009      This program is distributed in the hope that it will be useful,
010      but WITHOUT ANY WARRANTY; without even the implied warranty of
011      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
012      GNU Lesser General Public License for more details.
013    
014      You should have received a copy of the GNU Lesser General Public License
015      along with this program; if not, write to the Free Software
016      Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
017    
018    package org.objectweb.jac.util;
019    
020    import java.util.Collection;
021    import java.util.Iterator;
022    import java.util.List;
023    
024    
025    /**
026     * A Predicate class.
027     *
028     * @author <a href="mailto:laurent@aopsys.com">Laurent Martelli</a> 
029     */
030    
031    public abstract class Predicate {
032        public abstract boolean apply(Object object);
033        /**
034         * Keeps only the items matching the predicate from a collection
035         * @param in filter items from that collection
036         * @param out matching items are added to this collection
037         */
038        public void filter(Collection in, Collection out) {
039            Iterator i = in.iterator();
040            while (i.hasNext()) {
041                Object item = i.next();
042                if (apply(item)) {
043                    out.add(item);
044                }
045            }
046        }
047    }