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 * Compare two files using the {@link File#isDirectory()} method.
25 * <p>
26 * This comparator can be used to sort lists or arrays by directories and files.
27 * </p>
28 * <p>
29 * Example of sorting a list of files/directories using the {@link #DIRECTORY_COMPARATOR} singleton instance:
30 * </p>
31 *
32 * <pre>
33 * List<File> list = ...
34 * ((AbstractFileComparator) DirectoryFileComparator.DIRECTORY_COMPARATOR).sort(list);
35 * </pre>
36 * <p>
37 * Example of doing a <em>reverse</em> sort of an array of files/directories using the {@link #DIRECTORY_REVERSE}
38 * singleton instance:
39 * </p>
40 *
41 * <pre>
42 * File[] array = ...
43 * ((AbstractFileComparator) DirectoryFileComparator.DIRECTORY_REVERSE).sort(array);
44 * </pre>
45 * <h2>Deprecating Serialization</h2>
46 * <p>
47 * <em>Serialization is deprecated and will be removed in 3.0.</em>
48 * </p>
49 *
50 * @since 2.0
51 */
52 public class DirectoryFileComparator extends AbstractFileComparator implements Serializable {
53
54 private static final int TYPE_FILE = 2;
55
56 private static final int TYPE_DIRECTORY = 1;
57
58 private static final long serialVersionUID = 296132640160964395L;
59
60 /** Singleton default comparator instance */
61 public static final Comparator<File> DIRECTORY_COMPARATOR = new DirectoryFileComparator();
62
63 /** Singleton reverse default comparator instance */
64 public static final Comparator<File> DIRECTORY_REVERSE = new ReverseFileComparator(DIRECTORY_COMPARATOR);
65
66 /**
67 * Construct a new instance.
68 */
69 public DirectoryFileComparator() {
70 // empty
71 }
72
73 /**
74 * Compares the two files using the {@link File#isDirectory()} method.
75 *
76 * @param file1 The first file to compare.
77 * @param file2 The second file to compare.
78 * @return the result of calling file1's {@link File#compareTo(File)} with file2 as the parameter.
79 */
80 @Override
81 public int compare(final File file1, final File file2) {
82 return getType(file1) - getType(file2);
83 }
84
85 /**
86 * Converts type to numeric value.
87 *
88 * @param file The file.
89 * @return 1 for directories and 2 for files.
90 */
91 private int getType(final File file) {
92 return file.isDirectory() ? TYPE_DIRECTORY : TYPE_FILE;
93 }
94 }