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.comparators; 018 019 import java.util.Comparator; 020 021 import org.apache.commons.collections.Transformer; 022 023 /** 024 * Decorates another Comparator with transformation behavior. That is, the 025 * return value from the transform operation will be passed to the decorated 026 * {@link Comparator#compare(Object,Object) compare} method. 027 * 028 * @since Commons Collections 2.0 (?) 029 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $ 030 * 031 * @see org.apache.commons.collections.Transformer 032 * @see org.apache.commons.collections.comparators.ComparableComparator 033 */ 034 public class TransformingComparator implements Comparator { 035 036 /** The decorated comparator. */ 037 protected Comparator decorated; 038 /** The transformer being used. */ 039 protected Transformer transformer; 040 041 //----------------------------------------------------------------------- 042 /** 043 * Constructs an instance with the given Transformer and a 044 * {@link ComparableComparator ComparableComparator}. 045 * 046 * @param transformer what will transform the arguments to <code>compare</code> 047 */ 048 public TransformingComparator(Transformer transformer) { 049 this(transformer, new ComparableComparator()); 050 } 051 052 /** 053 * Constructs an instance with the given Transformer and Comparator. 054 * 055 * @param transformer what will transform the arguments to <code>compare</code> 056 * @param decorated the decorated Comparator 057 */ 058 public TransformingComparator(Transformer transformer, Comparator decorated) { 059 this.decorated = decorated; 060 this.transformer = transformer; 061 } 062 063 //----------------------------------------------------------------------- 064 /** 065 * Returns the result of comparing the values from the transform operation. 066 * 067 * @param obj1 the first object to transform then compare 068 * @param obj2 the second object to transform then compare 069 * @return negative if obj1 is less, positive if greater, zero if equal 070 */ 071 public int compare(Object obj1, Object obj2) { 072 Object value1 = this.transformer.transform(obj1); 073 Object value2 = this.transformer.transform(obj2); 074 return this.decorated.compare(value1, value2); 075 } 076 077 } 078