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    
018    package org.apache.commons.codec;
019    
020    import 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     */
034    public 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    }