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 import java.util.function.IntFunction;
23 import java.util.stream.Stream;
24 import java.util.stream.StreamSupport;
25
26 /**
27 * Compare two files using a set of delegate file {@link Comparator}.
28 * <p>
29 * This comparator can be used to sort lists or arrays of files by combining a number of other comparators.
30 * <p>
31 * Example of sorting a list of files by type (i.e. directory or file) and then by name:
32 *
33 * <pre>
34 * CompositeFileComparator comparator = new CompositeFileComparator(
35 * DirectoryFileComparator.DIRECTORY_COMPARATOR,
36 * NameFileComparator.NAME_COMPARATOR);
37 * List<File> list = ...
38 * comparator.sort(list);
39 * </pre>
40 * <h2>Deprecating Serialization</h2>
41 * <p>
42 * <em>Serialization is deprecated and will be removed in 3.0.</em>
43 * </p>
44 *
45 * @since 2.0
46 */
47 public class CompositeFileComparator extends AbstractFileComparator implements Serializable {
48
49 private static final Comparator<?>[] EMPTY_COMPARATOR_ARRAY = {};
50 private static final long serialVersionUID = -2224170307287243428L;
51
52 /**
53 * Delegates.
54 */
55 private final Comparator<File>[] delegates;
56
57 /**
58 * Constructs a composite comparator for the set of delegate comparators.
59 *
60 * @param delegates The delegate file comparators
61 */
62 public CompositeFileComparator(@SuppressWarnings("unchecked") final Comparator<File>... delegates) {
63 this.delegates = delegates == null ? emptyArray() : delegates.clone();
64 }
65
66 /**
67 * Constructs a composite comparator for the set of delegate comparators.
68 *
69 * @param delegates The delegate file comparators
70 */
71 public CompositeFileComparator(final Iterable<Comparator<File>> delegates) {
72 this.delegates = delegates == null ? emptyArray()
73 : StreamSupport.stream(delegates.spliterator(), false).toArray((IntFunction<Comparator<File>[]>) Comparator[]::new);
74 }
75
76 /**
77 * Compares the two files using delegate comparators.
78 *
79 * @param file1 The first file to compare
80 * @param file2 The second file to compare
81 * @return the first non-zero result returned from the delegate comparators or zero.
82 */
83 @Override
84 public int compare(final File file1, final File file2) {
85 return Stream.of(delegates).map(delegate -> delegate.compare(file1, file2)).filter(r -> r != 0).findFirst().orElse(0);
86 }
87
88 @SuppressWarnings("unchecked") // types are already correct
89 private Comparator<File>[] emptyArray() {
90 return (Comparator<File>[]) EMPTY_COMPARATOR_ARRAY;
91 }
92
93 /**
94 * String representation of this file comparator.
95 *
96 * @return String representation of this file comparator
97 */
98 @Override
99 public String toString() {
100 final StringBuilder builder = new StringBuilder();
101 builder.append(super.toString());
102 builder.append('{');
103 for (int i = 0; i < delegates.length; i++) {
104 if (i > 0) {
105 builder.append(',');
106 }
107 builder.append(delegates[i]);
108 }
109 builder.append('}');
110 return builder.toString();
111 }
112 }