001/*
002 *  Licensed to the Apache Software Foundation (ASF) under one
003 *  or more contributor license agreements.  See the NOTICE file
004 *  distributed with this work for additional information
005 *  regarding copyright ownership.  The ASF licenses this file
006 *  to you under the Apache License, Version 2.0 (the
007 *  "License"); you may not use this file except in compliance
008 *  with the License.  You may obtain a copy of the License at
009 *
010 *    http://www.apache.org/licenses/LICENSE-2.0
011 *
012 *  Unless required by applicable law or agreed to in writing,
013 *  software distributed under the License is distributed on an
014 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 *  KIND, either express or implied.  See the License for the
016 *  specific language governing permissions and limitations
017 *  under the License.
018 *
019 */
020package org.apache.directory.mavibot.btree.comparator;
021
022
023import java.util.Comparator;
024
025
026/**
027 * Compares Strings
028 *
029 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
030 */
031public class StringComparator implements Comparator<String>
032{
033    /** A static instance of a StringComparator */
034    public static final StringComparator INSTANCE = new StringComparator();
035
036    /**
037     * A private constructor of the StringComparator class
038     */
039    private StringComparator()
040    {
041    }
042
043
044    /**
045     * Compare two Strings.
046     *
047     * @param string1 First String
048     * @param string2 Second String
049     * @return 1 if string1 > String2, 0 if string1 == String2, -1 if string1 < String2
050     */
051    public int compare( String string1, String string2 )
052    {
053        if ( string1 == string2 )
054        {
055            return 0;
056        }
057
058        if ( string1 == null )
059        {
060            return -1;
061        }
062        else if ( string2 == null )
063        {
064            return 1;
065        }
066
067        int result = string1.compareTo( string2 );
068
069        if ( result < 0 )
070        {
071            return -1;
072        }
073        else if ( result > 0 )
074        {
075            return 1;
076        }
077        else
078        {
079            return 0;
080        }
081    }
082}