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 * Reverses the result of comparing two objects using
25 * the delegate {@link Comparator}.
26 *
27 * @since 1.4
28 */
29 class ReverseComparator extends AbstractFileComparator implements Serializable {
30
31 private static final long serialVersionUID = -4808255005272229056L;
32 private final Comparator<File> delegate;
33
34 /**
35 * Construct an instance with the specified delegate {@link Comparator}.
36 *
37 * @param delegate The comparator to delegate to
38 */
39 public ReverseComparator(final Comparator<File> delegate) {
40 if (delegate == null) {
41 throw new IllegalArgumentException("Delegate comparator is missing");
42 }
43 this.delegate = delegate;
44 }
45
46 /**
47 * Compare using the delegate Comparator, but reversing the result.
48 *
49 * @param file1 The first file to compare
50 * @param file2 The second file to compare
51 * @return the result from the delegate {@link Comparator#compare(Object, Object)}
52 * reversing the value (i.e. positive becomes negative and vice versa)
53 */
54 @Override
55 public int compare(final File file1, final File file2) {
56 return delegate.compare(file2, file1); // parameters switched round
57 }
58
59 /**
60 * String representation of this file comparator.
61 *
62 * @return String representation of this file comparator
63 */
64 @Override
65 public String toString() {
66 return super.toString() + "[" + delegate.toString() + "]";
67 }
68
69 }