001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.io.comparator;
018
019import java.io.File;
020import java.io.Serializable;
021import java.util.Comparator;
022
023import org.apache.commons.io.IOCase;
024
025/**
026 * Compare the <b>names</b> of two files for order (see {@link File#getName()}).
027 * <p>
028 * This comparator can be used to sort lists or arrays of files
029 * by their name either in a case-sensitive, case-insensitive or
030 * system dependent case-sensitive way. A number of singleton instances
031 * are provided for the various case sensitivity options (using {@link IOCase})
032 * and the reverse of those options.
033 * </p>
034 * <p>
035 * Example of a <i>case-sensitive</i> file name sort using the
036 * {@link #NAME_COMPARATOR} singleton instance:
037 * </p>
038 * <pre>
039 *       List&lt;File&gt; list = ...
040 *       ((AbstractFileComparator) NameFileComparator.NAME_COMPARATOR).sort(list);
041 * </pre>
042 * <p>
043 * Example of a <i>reverse case-insensitive</i> file name sort using the
044 * {@link #NAME_INSENSITIVE_REVERSE} singleton instance:
045 * </p>
046 * <pre>
047 *       File[] array = ...
048 *       ((AbstractFileComparator) NameFileComparator.NAME_INSENSITIVE_REVERSE).sort(array);
049 * </pre>
050 * <h2>Deprecating Serialization</h2>
051 * <p>
052 * <em>Serialization is deprecated and will be removed in 3.0.</em>
053 * </p>
054 *
055 * @since 1.4
056 */
057public class NameFileComparator extends AbstractFileComparator implements Serializable {
058
059    private static final long serialVersionUID = 8397947749814525798L;
060
061    /** Case-sensitive name comparator instance (see {@link IOCase#SENSITIVE}) */
062    public static final Comparator<File> NAME_COMPARATOR = new NameFileComparator();
063
064    /** Reverse case-sensitive name comparator instance (see {@link IOCase#SENSITIVE}) */
065    public static final Comparator<File> NAME_REVERSE = new ReverseFileComparator(NAME_COMPARATOR);
066
067    /** Case-insensitive name comparator instance (see {@link IOCase#INSENSITIVE}) */
068    public static final Comparator<File> NAME_INSENSITIVE_COMPARATOR = new NameFileComparator(IOCase.INSENSITIVE);
069
070    /** Reverse case-insensitive name comparator instance (see {@link IOCase#INSENSITIVE}) */
071    public static final Comparator<File> NAME_INSENSITIVE_REVERSE = new ReverseFileComparator(NAME_INSENSITIVE_COMPARATOR);
072
073    /** System sensitive name comparator instance (see {@link IOCase#SYSTEM}) */
074    public static final Comparator<File> NAME_SYSTEM_COMPARATOR = new NameFileComparator(IOCase.SYSTEM);
075
076    /** Reverse system sensitive name comparator instance (see {@link IOCase#SYSTEM}) */
077    public static final Comparator<File> NAME_SYSTEM_REVERSE = new ReverseFileComparator(NAME_SYSTEM_COMPARATOR);
078
079    /** Whether the comparison is case-sensitive. */
080    private final IOCase ioCase;
081
082    /**
083     * Constructs a case-sensitive file name comparator instance.
084     */
085    public NameFileComparator() {
086        this.ioCase = IOCase.SENSITIVE;
087    }
088
089    /**
090     * Constructs a file name comparator instance with the specified case-sensitivity.
091     *
092     * @param ioCase  how to handle case sensitivity, null means case-sensitive
093     */
094    public NameFileComparator(final IOCase ioCase) {
095        this.ioCase = IOCase.value(ioCase, IOCase.SENSITIVE);
096    }
097
098    /**
099     * Compares the names of two files with the specified case sensitivity.
100     *
101     * @param file1 The first file to compare
102     * @param file2 The second file to compare
103     * @return a negative value if the first file's name
104     * is less than the second, zero if the names are the
105     * same and a positive value if the first files name
106     * is greater than the second file.
107     */
108    @Override
109    public int compare(final File file1, final File file2) {
110        return ioCase.checkCompareTo(file1.getName(), file2.getName());
111    }
112
113    /**
114     * String representation of this file comparator.
115     *
116     * @return String representation of this file comparator
117     */
118    @Override
119    public String toString() {
120        return super.toString() + "[ioCase=" + ioCase + "]";
121    }
122}