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 }