001 /* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.commons.collections.functors; 018 019 import java.io.Serializable; 020 import java.util.Map; 021 022 import org.apache.commons.collections.Transformer; 023 024 /** 025 * Transformer implementation that returns the value held in a specified map 026 * using the input parameter as a key. 027 * 028 * @since Commons Collections 3.0 029 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $ 030 * 031 * @author Stephen Colebourne 032 */ 033 public final class MapTransformer implements Transformer, Serializable { 034 035 /** Serial version UID */ 036 private static final long serialVersionUID = 862391807045468939L; 037 038 /** The map of data to lookup in */ 039 private final Map iMap; 040 041 /** 042 * Factory to create the transformer. 043 * <p> 044 * If the map is null, a transformer that always returns null is returned. 045 * 046 * @param map the map, not cloned 047 * @return the transformer 048 */ 049 public static Transformer getInstance(Map map) { 050 if (map == null) { 051 return ConstantTransformer.NULL_INSTANCE; 052 } 053 return new MapTransformer(map); 054 } 055 056 /** 057 * Constructor that performs no validation. 058 * Use <code>getInstance</code> if you want that. 059 * 060 * @param map the map to use for lookup, not cloned 061 */ 062 private MapTransformer(Map map) { 063 super(); 064 iMap = map; 065 } 066 067 /** 068 * Transforms the input to result by looking it up in a <code>Map</code>. 069 * 070 * @param input the input object to transform 071 * @return the transformed result 072 */ 073 public Object transform(Object input) { 074 return iMap.get(input); 075 } 076 077 /** 078 * Gets the map to lookup in. 079 * 080 * @return the map 081 * @since Commons Collections 3.1 082 */ 083 public Map getMap() { 084 return iMap; 085 } 086 087 }