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.wiki.util.comparators;
021
022import org.apache.commons.lang3.StringUtils;
023
024import java.text.Collator;
025import java.util.Comparator;
026
027/**
028 * A comparator that sorts Strings using a Collator. This class is needed
029 * because, even though Collator implements
030 * <code>Comparator&lt;Object&gt;</code> and the required
031 * <code>compare(String, String)</code> method, you can't safely cast Collator
032 * to <code>Comparator&lt;String&gt;</code>.
033 * 
034 */
035public class CollatorComparator implements Comparator<String>
036{
037    // A special singleton instance for quick access
038    public static final Comparator<String> DEFAULT_LOCALE_COMPARATOR = new CollatorComparator();
039
040    protected Collator m_collator;
041
042    /**
043     * Default constructor uses the current locale's collator.
044     */
045    public CollatorComparator()
046    {
047        m_collator = Collator.getInstance();
048    }
049
050    /**
051     * Construct with a specific collator.
052     * 
053     * @param collator the collator to be used for comparisons
054     */
055    public CollatorComparator(final Collator collator )
056    {
057        m_collator = collator;
058    }
059
060    /*
061     * (non-Javadoc)
062     * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
063     */
064    public int compare(final String str1, final String str2 )
065    {
066        if( StringUtils.equals( str1, str2 ) ) {
067            return 0; // the same object
068        }
069        if( str1 == null ) {
070            return -1; // str1 is null and str2 isn't so str1 is smaller
071        }
072        if( str2 == null ) {
073            return 1; // str2 is null and str1 isn't so str1 is bigger
074        }
075        return m_collator.compare( str1, str2 );
076    }
077
078    /**
079     * Specify a new collator.
080     * 
081     * @param collator the collator to be used from now on
082     */
083    public void setCollator(final Collator collator )
084    {
085        m_collator = collator;
086    }
087}