001    /*
002     * Copyright (C) 2008-2010 by Holger Arndt
003     *
004     * This file is part of the Universal Java Matrix Package (UJMP).
005     * See the NOTICE file distributed with this work for additional
006     * information regarding copyright ownership and licensing.
007     *
008     * UJMP is free software; you can redistribute it and/or modify
009     * it under the terms of the GNU Lesser General Public License as
010     * published by the Free Software Foundation; either version 2
011     * of the License, or (at your option) any later version.
012     *
013     * UJMP is distributed in the hope that it will be useful,
014     * but WITHOUT ANY WARRANTY; without even the implied warranty of
015     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
016     * GNU Lesser General Public License for more details.
017     *
018     * You should have received a copy of the GNU Lesser General Public
019     * License along with UJMP; if not, write to the
020     * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
021     * Boston, MA  02110-1301  USA
022     */
023    
024    package org.ujmp.core.collections;
025    
026    import java.util.HashMap;
027    import java.util.Map;
028    import java.util.Set;
029    import java.util.concurrent.Callable;
030    
031    public class LazyMap<K, V> extends AbstractMap<K, V> {
032            private static final long serialVersionUID = -5970508001189550492L;
033    
034            private transient Map<K, Callable<V>> map = null;
035    
036            public LazyMap() {
037            }
038    
039            private Map<K, Callable<V>> getMap() {
040                    if (map == null) {
041                            map = new HashMap<K, Callable<V>>();
042                    }
043                    return map;
044            }
045    
046            public void clear() {
047                    getMap().clear();
048            }
049    
050            public V get(Object key) {
051                    Callable<V> cv = getMap().get(key);
052                    if (cv == null) {
053                            return null;
054                    }
055                    try {
056                            return cv.call();
057                    } catch (Exception e) {
058                            e.printStackTrace();
059                            return null;
060                    }
061            }
062    
063            public Set<K> keySet() {
064                    return getMap().keySet();
065            }
066    
067            public void put(K key, Callable<V> value) {
068                    getMap().put(key, value);
069            }
070    
071            public V put(K key, final V value) {
072                    put(key, new Callable<V>() {
073    
074                            public V call() throws Exception {
075                                    return value;
076                            }
077                    });
078                    return null;
079            }
080    
081            public V remove(Object key) {
082                    getMap().remove(key);
083                    return null;
084            }
085    
086            public int size() {
087                    return getMap().size();
088            }
089    
090    }