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 */ 017package org.apache.commons.io.comparator; 018 019import java.io.File; 020import java.io.Serializable; 021import java.util.Comparator; 022import java.util.stream.Stream; 023import java.util.stream.StreamSupport; 024 025/** 026 * Compare two files using a set of delegate file {@link Comparator}. 027 * <p> 028 * This comparator can be used to sort lists or arrays of files by combining a number of other comparators. 029 * <p> 030 * Example of sorting a list of files by type (i.e. directory or file) and then by name: 031 * 032 * <pre> 033 * CompositeFileComparator comparator = new CompositeFileComparator( 034 * DirectoryFileComparator.DIRECTORY_COMPARATOR, 035 * NameFileComparator.NAME_COMPARATOR); 036 * List<File> list = ... 037 * comparator.sort(list); 038 * </pre> 039 * <h2>Deprecating Serialization</h2> 040 * <p> 041 * <em>Serialization is deprecated and will be removed in 3.0.</em> 042 * </p> 043 * 044 * @since 2.0 045 */ 046public class CompositeFileComparator extends AbstractFileComparator implements Serializable { 047 048 private static final Comparator<?>[] EMPTY_COMPARATOR_ARRAY = {}; 049 private static final long serialVersionUID = -2224170307287243428L; 050 051 private final Comparator<File>[] delegates; 052 053 /** 054 * Constructs a composite comparator for the set of delegate comparators. 055 * 056 * @param delegates The delegate file comparators 057 */ 058 public CompositeFileComparator(@SuppressWarnings("unchecked") final Comparator<File>... delegates) { 059 this.delegates = delegates == null ? emptyArray() : delegates.clone(); 060 } 061 062 /** 063 * Constructs a composite comparator for the set of delegate comparators. 064 * 065 * @param delegates The delegate file comparators 066 */ 067 public CompositeFileComparator(final Iterable<Comparator<File>> delegates) { 068 this.delegates = delegates == null ? emptyArray() : StreamSupport.stream(delegates.spliterator(), false).toArray(Comparator[]::new); 069 } 070 071 /** 072 * Compares the two files using delegate comparators. 073 * 074 * @param file1 The first file to compare 075 * @param file2 The second file to compare 076 * @return the first non-zero result returned from the delegate comparators or zero. 077 */ 078 @Override 079 public int compare(final File file1, final File file2) { 080 return Stream.of(delegates).map(delegate -> delegate.compare(file1, file2)).filter(r -> r != 0).findFirst().orElse(0); 081 } 082 083 @SuppressWarnings("unchecked") // types are already correct 084 private Comparator<File>[] emptyArray() { 085 return (Comparator<File>[]) EMPTY_COMPARATOR_ARRAY; 086 } 087 088 /** 089 * String representation of this file comparator. 090 * 091 * @return String representation of this file comparator 092 */ 093 @Override 094 public String toString() { 095 final StringBuilder builder = new StringBuilder(); 096 builder.append(super.toString()); 097 builder.append('{'); 098 for (int i = 0; i < delegates.length; i++) { 099 if (i > 0) { 100 builder.append(','); 101 } 102 builder.append(delegates[i]); 103 } 104 builder.append('}'); 105 return builder.toString(); 106 } 107}