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.io.comparator; 18 19 import java.io.Serializable; 20 import java.util.Comparator; 21 22 /** 23 * Reverses the result of comparing two objects using 24 * the delegate {@link Comparator}. 25 * 26 * @version $Revision: 609243 $ $Date: 2008-01-06 00:30:42 +0000 (Sun, 06 Jan 2008) $ 27 * @since Commons IO 1.4 28 */ 29 class ReverseComparator<T> implements Comparator<T>, Serializable { 30 31 private final Comparator<T> delegate; 32 33 /** 34 * Construct an instance with the sepecified delegate {@link Comparator}. 35 * 36 * @param delegate The comparator to delegate to 37 */ 38 public ReverseComparator(Comparator<T> delegate) { 39 if (delegate == null) { 40 throw new IllegalArgumentException("Delegate comparator is missing"); 41 } 42 this.delegate = delegate; 43 } 44 45 /** 46 * Compare using the delegate Comparator, but reversing the result. 47 * 48 * @param obj1 The first object to compare 49 * @param obj2 The second object to compare 50 * @return the result from the delegate {@link Comparator#compare(Object, Object)} 51 * reversing the value (i.e. positive becomes negative and vice versa) 52 */ 53 public int compare(T obj1, T obj2) { 54 return delegate.compare(obj2, obj1); // parameters switched round 55 } 56 57 } 58
