1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.functor.example.map;
18
19 import java.util.Map;
20
21 import org.apache.commons.functor.BinaryFunction;
22 import org.apache.commons.functor.UnaryFunction;
23
24 /**
25 * @version $Revision: 666157 $ $Date: 2008-06-10 17:34:23 +0200 (Tue, 10 Jun 2008) $
26 * @author Rodney Waldhoff
27 */
28 @SuppressWarnings("unchecked")
29 public class LazyMap extends FunctoredMap {
30 public LazyMap(Map map, final UnaryFunction factory) {
31 super(map);
32 setOnGet(new BinaryFunction() {
33 public Object evaluate(Object m, Object key) {
34 Map map = (Map) m;
35 if (map.containsKey(key)) {
36 return map.get(key);
37 } else {
38 Object value = factory.evaluate(key);
39 map.put(key,value);
40 return value;
41 }
42 }
43 });
44 }
45 }