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     * Compares Strings using a {@link StringEncoder}. This comparator is used to sort Strings by an encoding scheme such as
024     * Soundex, Metaphone, etc. This class can come in handy if one need to sort Strings by an encoded form of a name such
025     * as Soundex.
026     *
027     * <p>This class is immutable and thread-safe.</p>
028     *
029     * @version $Id: StringEncoderComparator.html 889935 2013-12-11 05:05:13Z ggregory $
030     */
031    @SuppressWarnings("rawtypes")
032    // TODO ought to implement Comparator<String> but that's not possible whilst maintaining binary compatibility.
033    public class StringEncoderComparator implements Comparator {
034    
035        /**
036         * Internal encoder instance.
037         */
038        private final StringEncoder stringEncoder;
039    
040        /**
041         * Constructs a new instance.
042         *
043         * @deprecated Creating an instance without a {@link StringEncoder} leads to a {@link NullPointerException}. Will be
044         *             removed in 2.0.
045         */
046        @Deprecated
047        public StringEncoderComparator() {
048            this.stringEncoder = null; // Trying to use this will cause things to break
049        }
050    
051        /**
052         * Constructs a new instance with the given algorithm.
053         *
054         * @param stringEncoder
055         *            the StringEncoder used for comparisons.
056         */
057        public StringEncoderComparator(final StringEncoder stringEncoder) {
058            this.stringEncoder = stringEncoder;
059        }
060    
061        /**
062         * Compares two strings based not on the strings themselves, but on an encoding of the two strings using the
063         * StringEncoder this Comparator was created with.
064         *
065         * If an {@link EncoderException} is encountered, return <code>0</code>.
066         *
067         * @param o1
068         *            the object to compare
069         * @param o2
070         *            the object to compare to
071         * @return the Comparable.compareTo() return code or 0 if an encoding error was caught.
072         * @see Comparable
073         */
074        @Override
075        public int compare(final Object o1, final Object o2) {
076    
077            int compareCode = 0;
078    
079            try {
080                @SuppressWarnings("unchecked") // May fail with CCE if encode returns something that is not Comparable
081                // However this was always the case.
082                final Comparable<Comparable<?>> s1 = (Comparable<Comparable<?>>) this.stringEncoder.encode(o1);
083                final Comparable<?> s2 = (Comparable<?>) this.stringEncoder.encode(o2);
084                compareCode = s1.compareTo(s2);
085            } catch (final EncoderException ee) {
086                compareCode = 0;
087            }
088            return compareCode;
089        }
090    
091    }