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 * Example of a <i>case-sensitive</i> file name sort using the
035 * {@link #NAME_COMPARATOR} singleton instance:
036 * <pre>
037 *       List&lt;File&gt; list = ...
038 *       ((AbstractFileComparator) NameFileComparator.NAME_COMPARATOR).sort(list);
039 * </pre>
040 * <p>
041 * Example of a <i>reverse case-insensitive</i> file name sort using the
042 * {@link #NAME_INSENSITIVE_REVERSE} singleton instance:
043 * <pre>
044 *       File[] array = ...
045 *       ((AbstractFileComparator) NameFileComparator.NAME_INSENSITIVE_REVERSE).sort(array);
046 * </pre>
047 * <p>
048 *
049 * @since 1.4
050 */
051public class NameFileComparator extends AbstractFileComparator implements Serializable {
052
053    private static final long serialVersionUID = 8397947749814525798L;
054
055    /** Case-sensitive name comparator instance (see {@link IOCase#SENSITIVE}) */
056    public static final Comparator<File> NAME_COMPARATOR = new NameFileComparator();
057
058    /** Reverse case-sensitive name comparator instance (see {@link IOCase#SENSITIVE}) */
059    public static final Comparator<File> NAME_REVERSE = new ReverseFileComparator(NAME_COMPARATOR);
060
061    /** Case-insensitive name comparator instance (see {@link IOCase#INSENSITIVE}) */
062    public static final Comparator<File> NAME_INSENSITIVE_COMPARATOR = new NameFileComparator(IOCase.INSENSITIVE);
063
064    /** Reverse case-insensitive name comparator instance (see {@link IOCase#INSENSITIVE}) */
065    public static final Comparator<File> NAME_INSENSITIVE_REVERSE = new ReverseFileComparator(NAME_INSENSITIVE_COMPARATOR);
066
067    /** System sensitive name comparator instance (see {@link IOCase#SYSTEM}) */
068    public static final Comparator<File> NAME_SYSTEM_COMPARATOR = new NameFileComparator(IOCase.SYSTEM);
069
070    /** Reverse system sensitive name comparator instance (see {@link IOCase#SYSTEM}) */
071    public static final Comparator<File> NAME_SYSTEM_REVERSE = new ReverseFileComparator(NAME_SYSTEM_COMPARATOR);
072
073    /** Whether the comparison is case sensitive. */
074    private final IOCase caseSensitivity;
075
076    /**
077     * Construct a case sensitive file name comparator instance.
078     */
079    public NameFileComparator() {
080        this.caseSensitivity = IOCase.SENSITIVE;
081    }
082
083    /**
084     * Construct a file name comparator instance with the specified case-sensitivity.
085     *
086     * @param caseSensitivity  how to handle case sensitivity, null means case-sensitive
087     */
088    public NameFileComparator(final IOCase caseSensitivity) {
089        this.caseSensitivity = caseSensitivity == null ? IOCase.SENSITIVE : caseSensitivity;
090    }
091
092    /**
093     * Compare the names of two files with the specified case sensitivity.
094     *
095     * @param file1 The first file to compare
096     * @param file2 The second file to compare
097     * @return a negative value if the first file's name
098     * is less than the second, zero if the names are the
099     * same and a positive value if the first files name
100     * is greater than the second file.
101     */
102    @Override
103    public int compare(final File file1, final File file2) {
104        return caseSensitivity.checkCompareTo(file1.getName(), file2.getName());
105    }
106
107    /**
108     * String representation of this file comparator.
109     *
110     * @return String representation of this file comparator
111     */
112    @Override
113    public String toString() {
114        return super.toString() + "[caseSensitivity=" + caseSensitivity + "]";
115    }
116}