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 *      https://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;
021import java.util.Objects;
022
023/**
024 * Compares Strings using a {@link StringEncoder}. This comparator is used to sort Strings by an encoding scheme such as Soundex, Metaphone, etc. This class can
025 * come in handy if one need to sort Strings by an encoded form of a name such as Soundex.
026 * <p>
027 * This class is immutable and thread-safe.
028 * </p>
029 */
030@SuppressWarnings("rawtypes")
031// TODO ought to implement Comparator<String> but that's not possible whilst maintaining binary compatibility.
032public class StringEncoderComparator implements Comparator {
033
034    /**
035     * Internal encoder instance.
036     */
037    private final StringEncoder stringEncoder;
038
039    /**
040     * Constructs a new instance.
041     *
042     * @deprecated Creating an instance without a {@link StringEncoder} leads to a {@link NullPointerException}. Will be removed in 2.0.
043     */
044    @Deprecated
045    public StringEncoderComparator() {
046        this.stringEncoder = null; // Trying to use this will cause things to break
047    }
048
049    /**
050     * Constructs a new instance with the given algorithm.
051     *
052     * @param stringEncoder the StringEncoder used for comparisons.
053     * @throws NullPointerException if the StringEncoder is null.
054     */
055    public StringEncoderComparator(final StringEncoder stringEncoder) {
056        this.stringEncoder = Objects.requireNonNull(stringEncoder, "stringEncoder");
057    }
058
059    /**
060     * Compares two strings based not on the strings themselves, but on an encoding of the two strings using the StringEncoder this Comparator was created with.
061     * If an {@link EncoderException} is encountered, return {@code 0}.
062     *
063     * @param o1 the object to compare.
064     * @param o2 the object to compare to.
065     * @return The Comparable.compareTo() return code or 0 if an encoding error was caught.
066     * @see Comparable
067     */
068    @Override
069    public int compare(final Object o1, final Object o2) {
070        int compareCode = 0;
071        try {
072            @SuppressWarnings("unchecked") // May fail with CCE if encode returns something that is not Comparable
073            // However this was always the case.
074            final Comparable<Comparable<?>> s1 = (Comparable<Comparable<?>>) stringEncoder.encode(o1);
075            final Comparable<?> s2 = (Comparable<?>) stringEncoder.encode(o2);
076            compareCode = s1.compareTo(s2);
077        } catch (final EncoderException ee) {
078            compareCode = 0;
079        }
080        return compareCode;
081    }
082}