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 import org.apache.commons.io.FilenameUtils; 24 import org.apache.commons.io.IOCase; 25 26 /** 27 * Compare the file name <b>extensions</b> for order 28 * (see {@link FilenameUtils#getExtension(String)}). 29 * <p> 30 * This comparator can be used to sort lists or arrays of files 31 * by their file extension either in a case-sensitive, case-insensitive or 32 * system dependant case sensitive way. A number of singleton instances 33 * are provided for the various case sensitivity options (using {@link IOCase}) 34 * and the reverse of those options. 35 * <p> 36 * Example of a <i>case-sensitive</i> file extension sort using the 37 * {@link #EXTENSION_COMPARATOR} singleton instance: 38 * <pre> 39 * List<File> list = ... 40 * Collections.sort(list, ExtensionFileComparator.EXTENSION_COMPARATOR); 41 * </pre> 42 * <p> 43 * Example of a <i>reverse case-insensitive</i> file extension sort using the 44 * {@link #EXTENSION_INSENSITIVE_REVERSE} singleton instance: 45 * <pre> 46 * File[] array = ... 47 * Arrays.sort(array, ExtensionFileComparator.EXTENSION_INSENSITIVE_REVERSE); 48 * </pre> 49 * <p> 50 * 51 * @version $Revision: 609243 $ $Date: 2008-01-06 00:30:42 +0000 (Sun, 06 Jan 2008) $ 52 * @since Commons IO 1.4 53 */ 54 public class ExtensionFileComparator implements Comparator<File>, Serializable { 55 56 /** Case-sensitive extension comparator instance (see {@link IOCase#SENSITIVE}) */ 57 public static final Comparator<File> EXTENSION_COMPARATOR = new ExtensionFileComparator(); 58 59 /** Reverse case-sensitive extension comparator instance (see {@link IOCase#SENSITIVE}) */ 60 public static final Comparator<File> EXTENSION_REVERSE = new ReverseComparator<File>(EXTENSION_COMPARATOR); 61 62 /** Case-insensitive extension comparator instance (see {@link IOCase#INSENSITIVE}) */ 63 public static final Comparator<File> EXTENSION_INSENSITIVE_COMPARATOR = new ExtensionFileComparator(IOCase.INSENSITIVE); 64 65 /** Reverse case-insensitive extension comparator instance (see {@link IOCase#INSENSITIVE}) */ 66 public static final Comparator<File> EXTENSION_INSENSITIVE_REVERSE 67 = new ReverseComparator<File>(EXTENSION_INSENSITIVE_COMPARATOR); 68 69 /** System sensitive extension comparator instance (see {@link IOCase#SYSTEM}) */ 70 public static final Comparator<File> EXTENSION_SYSTEM_COMPARATOR = new ExtensionFileComparator(IOCase.SYSTEM); 71 72 /** Reverse system sensitive path comparator instance (see {@link IOCase#SYSTEM}) */ 73 public static final Comparator<File> EXTENSION_SYSTEM_REVERSE = new ReverseComparator<File>(EXTENSION_SYSTEM_COMPARATOR); 74 75 /** Whether the comparison is case sensitive. */ 76 private final IOCase caseSensitivity; 77 78 /** 79 * Construct a case sensitive file extension comparator instance. 80 */ 81 public ExtensionFileComparator() { 82 this.caseSensitivity = IOCase.SENSITIVE; 83 } 84 85 /** 86 * Construct a file extension comparator instance with the specified case-sensitivity. 87 * 88 * @param caseSensitivity how to handle case sensitivity, null means case-sensitive 89 */ 90 public ExtensionFileComparator(IOCase caseSensitivity) { 91 this.caseSensitivity = caseSensitivity == null ? IOCase.SENSITIVE : caseSensitivity; 92 } 93 94 /** 95 * Compare the extensions of two files the specified case sensitivity. 96 * 97 * @param obj1 The first file to compare 98 * @param obj2 The second file to compare 99 * @return a negative value if the first file's extension 100 * is less than the second, zero if the extensions are the 101 * same and a positive value if the first files extension 102 * is greater than the second file. 103 * 104 */ 105 public int compare(File file1, File file2) { 106 String suffix1 = FilenameUtils.getExtension(file1.getName()); 107 String suffix2 = FilenameUtils.getExtension(file2.getName()); 108 return caseSensitivity.checkCompareTo(suffix1, suffix2); 109 } 110 } 111