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 * 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 928559 2014-11-10 02:53:54Z ggregory $
030 */
031@SuppressWarnings("rawtypes")
032// TODO ought to implement Comparator<String> but that's not possible whilst maintaining binary compatibility.
033public 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}