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.File; 20 import java.io.Serializable; 21 import java.util.Comparator; 22 23 /** 24 * Reverses the result of comparing two objects using 25 * the delegate {@link Comparator}. 26 * 27 * @since 1.4 28 */ 29 class ReverseComparator extends AbstractFileComparator implements Serializable { 30 31 private static final long serialVersionUID = -4808255005272229056L; 32 private final Comparator<File> delegate; 33 34 /** 35 * Construct an instance with the specified delegate {@link Comparator}. 36 * 37 * @param delegate The comparator to delegate to 38 */ 39 public ReverseComparator(final Comparator<File> delegate) { 40 if (delegate == null) { 41 throw new IllegalArgumentException("Delegate comparator is missing"); 42 } 43 this.delegate = delegate; 44 } 45 46 /** 47 * Compare using the delegate Comparator, but reversing the result. 48 * 49 * @param file1 The first file to compare 50 * @param file2 The second file to compare 51 * @return the result from the delegate {@link Comparator#compare(Object, Object)} 52 * reversing the value (i.e. positive becomes negative and vice versa) 53 */ 54 @Override 55 public int compare(final File file1, final File file2) { 56 return delegate.compare(file2, file1); // parameters switched round 57 } 58 59 /** 60 * String representation of this file comparator. 61 * 62 * @return String representation of this file comparator 63 */ 64 @Override 65 public String toString() { 66 return super.toString() + "[" + delegate.toString() + "]"; 67 } 68 69 }