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Commons IO example source code file (ExtensionFileComparator.java)

This example Commons IO source code file (ExtensionFileComparator.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons IO tags/keywords

comparator, comparator, extension_comparator, extension_reverse, extension_system_reverse, extensionfilecomparator, extensionfilecomparator, file, io, override, reversecomparator, reversecomparator, serializable, string, string, util

The Commons IO ExtensionFileComparator.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.io.comparator;

import java.io.File;
import java.io.Serializable;
import java.util.Comparator;

import org.apache.commons.io.FilenameUtils;
import org.apache.commons.io.IOCase;

/**
 * Compare the file name <b>extensions for order
 * (see {@link FilenameUtils#getExtension(String)}).
 * <p>
 * This comparator can be used to sort lists or arrays of files
 * by their file extension either in a case-sensitive, case-insensitive or
 * system dependant case sensitive way. A number of singleton instances
 * are provided for the various case sensitivity options (using {@link IOCase})
 * and the reverse of those options.
 * <p>
 * Example of a <i>case-sensitive file extension sort using the
 * {@link #EXTENSION_COMPARATOR} singleton instance:
 * <pre>
 *       List<File> list = ...
 *       ExtensionFileComparator.EXTENSION_COMPARATOR.sort(list);
 * </pre>
 * <p>
 * Example of a <i>reverse case-insensitive file extension sort using the
 * {@link #EXTENSION_INSENSITIVE_REVERSE} singleton instance:
 * <pre>
 *       File[] array = ...
 *       ExtensionFileComparator.EXTENSION_INSENSITIVE_REVERSE.sort(array);
 * </pre>
 * <p>
 *
 * @version $Revision: 1003216 $ $Date: 2010-09-30 20:39:21 +0100 (Thu, 30 Sep 2010) $
 * @since Commons IO 1.4
 */
public class ExtensionFileComparator extends AbstractFileComparator implements Serializable {

    /** Case-sensitive extension comparator instance (see {@link IOCase#SENSITIVE}) */
    public static final Comparator<File> EXTENSION_COMPARATOR = new ExtensionFileComparator();

    /** Reverse case-sensitive extension comparator instance (see {@link IOCase#SENSITIVE}) */
    public static final Comparator<File> EXTENSION_REVERSE = new ReverseComparator(EXTENSION_COMPARATOR);

    /** Case-insensitive extension comparator instance (see {@link IOCase#INSENSITIVE}) */
    public static final Comparator<File> EXTENSION_INSENSITIVE_COMPARATOR
                                                = new ExtensionFileComparator(IOCase.INSENSITIVE);

    /** Reverse case-insensitive extension comparator instance (see {@link IOCase#INSENSITIVE}) */
    public static final Comparator<File> EXTENSION_INSENSITIVE_REVERSE
                                                = new ReverseComparator(EXTENSION_INSENSITIVE_COMPARATOR);

    /** System sensitive extension comparator instance (see {@link IOCase#SYSTEM}) */
    public static final Comparator<File> EXTENSION_SYSTEM_COMPARATOR = new ExtensionFileComparator(IOCase.SYSTEM);

    /** Reverse system sensitive path comparator instance (see {@link IOCase#SYSTEM}) */
    public static final Comparator<File> EXTENSION_SYSTEM_REVERSE = new ReverseComparator(EXTENSION_SYSTEM_COMPARATOR);

    /** Whether the comparison is case sensitive. */
    private final IOCase caseSensitivity;

    /**
     * Construct a case sensitive file extension comparator instance.
     */
    public ExtensionFileComparator() {
        this.caseSensitivity = IOCase.SENSITIVE;
    }

    /**
     * Construct a file extension comparator instance with the specified case-sensitivity.
     *
     * @param caseSensitivity how to handle case sensitivity, null means case-sensitive
     */
    public ExtensionFileComparator(IOCase caseSensitivity) {
        this.caseSensitivity = caseSensitivity == null ? IOCase.SENSITIVE : caseSensitivity;
    }

    /**
     * Compare the extensions of two files the specified case sensitivity.
     * 
     * @param file1 The first file to compare
     * @param file2 The second file to compare
     * @return a negative value if the first file's extension
     * is less than the second, zero if the extensions are the
     * same and a positive value if the first files extension
     * is greater than the second file.
     * 
     */
    public int compare(File file1, File file2) {
        String suffix1 = FilenameUtils.getExtension(file1.getName());
        String suffix2 = FilenameUtils.getExtension(file2.getName());
        return caseSensitivity.checkCompareTo(suffix1, suffix2);
    }

    /**
     * String representation of this file comparator.
     *
     * @return String representation of this file comparator
     */
    @Override
    public String toString() {
        return super.toString() + "[caseSensitivity=" + caseSensitivity + "]";
    }
}

Other Commons IO examples (source code examples)

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