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; 022 023import org.apache.commons.io.FilenameUtils; 024import org.apache.commons.io.IOCase; 025 026/** 027 * Compare the file name <b>extensions</b> for order 028 * (see {@link FilenameUtils#getExtension(String)}). 029 * <p> 030 * This comparator can be used to sort lists or arrays of files 031 * by their file extension either in a case-sensitive, case-insensitive or 032 * system dependent case sensitive way. A number of singleton instances 033 * are provided for the various case sensitivity options (using {@link IOCase}) 034 * and the reverse of those options. 035 * <p> 036 * Example of a <i>case-sensitive</i> file extension sort using the 037 * {@link #EXTENSION_COMPARATOR} singleton instance: 038 * <pre> 039 * List<File> list = ... 040 * ((AbstractFileComparator) ExtensionFileComparator.EXTENSION_COMPARATOR).sort(list); 041 * </pre> 042 * <p> 043 * Example of a <i>reverse case-insensitive</i> file extension sort using the 044 * {@link #EXTENSION_INSENSITIVE_REVERSE} singleton instance: 045 * <pre> 046 * File[] array = ... 047 * ((AbstractFileComparator) ExtensionFileComparator.EXTENSION_INSENSITIVE_REVERSE).sort(array); 048 * </pre> 049 * <p> 050 * 051 * @since 1.4 052 */ 053public class ExtensionFileComparator extends AbstractFileComparator implements Serializable { 054 055 private static final long serialVersionUID = 1928235200184222815L; 056 057 /** Case-sensitive extension comparator instance (see {@link IOCase#SENSITIVE}) */ 058 public static final Comparator<File> EXTENSION_COMPARATOR = new ExtensionFileComparator(); 059 060 /** Reverse case-sensitive extension comparator instance (see {@link IOCase#SENSITIVE}) */ 061 public static final Comparator<File> EXTENSION_REVERSE = new ReverseComparator(EXTENSION_COMPARATOR); 062 063 /** Case-insensitive extension comparator instance (see {@link IOCase#INSENSITIVE}) */ 064 public static final Comparator<File> EXTENSION_INSENSITIVE_COMPARATOR 065 = new ExtensionFileComparator(IOCase.INSENSITIVE); 066 067 /** Reverse case-insensitive extension comparator instance (see {@link IOCase#INSENSITIVE}) */ 068 public static final Comparator<File> EXTENSION_INSENSITIVE_REVERSE 069 = new ReverseComparator(EXTENSION_INSENSITIVE_COMPARATOR); 070 071 /** System sensitive extension comparator instance (see {@link IOCase#SYSTEM}) */ 072 public static final Comparator<File> EXTENSION_SYSTEM_COMPARATOR = new ExtensionFileComparator(IOCase.SYSTEM); 073 074 /** Reverse system sensitive path comparator instance (see {@link IOCase#SYSTEM}) */ 075 public static final Comparator<File> EXTENSION_SYSTEM_REVERSE = new ReverseComparator(EXTENSION_SYSTEM_COMPARATOR); 076 077 /** Whether the comparison is case sensitive. */ 078 private final IOCase caseSensitivity; 079 080 /** 081 * Construct a case sensitive file extension comparator instance. 082 */ 083 public ExtensionFileComparator() { 084 this.caseSensitivity = IOCase.SENSITIVE; 085 } 086 087 /** 088 * Construct a file extension comparator instance with the specified case-sensitivity. 089 * 090 * @param caseSensitivity how to handle case sensitivity, null means case-sensitive 091 */ 092 public ExtensionFileComparator(final IOCase caseSensitivity) { 093 this.caseSensitivity = caseSensitivity == null ? IOCase.SENSITIVE : caseSensitivity; 094 } 095 096 /** 097 * Compare the extensions of two files the specified case sensitivity. 098 * 099 * @param file1 The first file to compare 100 * @param file2 The second file to compare 101 * @return a negative value if the first file's extension 102 * is less than the second, zero if the extensions are the 103 * same and a positive value if the first files extension 104 * is greater than the second file. 105 * 106 */ 107 @Override 108 public int compare(final File file1, final File file2) { 109 final String suffix1 = FilenameUtils.getExtension(file1.getName()); 110 final String suffix2 = FilenameUtils.getExtension(file2.getName()); 111 return caseSensitivity.checkCompareTo(suffix1, suffix2); 112 } 113 114 /** 115 * String representation of this file comparator. 116 * 117 * @return String representation of this file comparator 118 */ 119 @Override 120 public String toString() { 121 return super.toString() + "[caseSensitivity=" + caseSensitivity + "]"; 122 } 123}