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