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