    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}