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 */
017
018package org.apache.commons.codec;
019
020import java.util.Comparator;
021
022/**
023 * Strings are comparable, and this comparator allows 
024 * you to configure it with an instance of a class
025 * which implements StringEncoder.  This comparator
026 * is used to sort Strings by an encoding scheme such
027 * as Soundex, Metaphone, etc.  This class can come in
028 * handy if one need to sort Strings by an encoded
029 * form of a name such as Soundex.
030 *
031 * @author Apache Software Foundation
032 * @version $Id: StringEncoderComparator.java 793391 2009-07-12 18:38:08Z ggregory $
033 */
034public class StringEncoderComparator implements Comparator {
035
036    /**
037     * Internal encoder instance.
038     */
039    private final StringEncoder stringEncoder;
040
041    /**
042     * Constructs a new instance.
043     * @deprecated as creating without a StringEncoder will lead to a 
044     *             broken NullPointerException creating comparator.
045     */
046    public StringEncoderComparator() {
047        this.stringEncoder = null;   // Trying to use this will cause things to break
048    }
049
050    /**
051     * Constructs a new instance with the given algorithm.
052     * @param stringEncoder the StringEncoder used for comparisons.
053     */
054    public StringEncoderComparator(StringEncoder stringEncoder) {
055        this.stringEncoder = stringEncoder;
056    }
057
058    /**
059     * Compares two strings based not on the strings 
060     * themselves, but on an encoding of the two 
061     * strings using the StringEncoder this Comparator
062     * was created with.
063     * 
064     * If an {@link EncoderException} is encountered, return <code>0</code>.
065     * 
066     * @param o1 the object to compare
067     * @param o2 the object to compare to
068     * @return the Comparable.compareTo() return code or 0 if an encoding error was caught.
069     * @see Comparable
070     */
071    public int compare(Object o1, Object o2) {
072
073        int compareCode = 0;
074
075        try {
076            Comparable s1 = (Comparable) this.stringEncoder.encode(o1);
077            Comparable s2 = (Comparable) this.stringEncoder.encode(o2);
078            compareCode = s1.compareTo(s2);
079        } 
080        catch (EncoderException ee) {
081            compareCode = 0;
082        }
083        return compareCode;
084    }
085
086}