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The Apache Commons Codec package contains simple encoder and decoders for various formats such as Base64 and Hexadecimal. In addition to these widely used encoders and decoders, the codec package also maintains a collection of phonetic encoding utilities.

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.codec;

import java.util.Comparator;

/**
 * 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 come in handy if one need to sort Strings by an encoded form of a name such
 * as Soundex.
 *
 * This class is immutable and thread-safe.
 *
 * @version $Id$
 */
@SuppressWarnings("rawtypes")
// TODO ought to implement Comparator but that's not possible whilst maintaining binary compatibility.
public class StringEncoderComparator implements Comparator {

    /**
     * Internal encoder instance.
     */
    private final StringEncoder stringEncoder;

    /**
     * Constructs a new instance.
     *
     * @deprecated Creating an instance without a {@link StringEncoder} leads to a {@link NullPointerException}. Will be
     *             removed in 2.0.
     */
    @Deprecated
    public StringEncoderComparator() {
        this.stringEncoder = null; // Trying to use this will cause things to break
    }

    /**
     * Constructs a new instance with the given algorithm.
     *
     * @param stringEncoder
     *            the StringEncoder used for comparisons.
     */
    public StringEncoderComparator(final StringEncoder stringEncoder) {
        this.stringEncoder = stringEncoder;
    }

    /**
     * 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.
     *
     * If an {@link EncoderException} is encountered, return 0.
     *
     * @param o1
     *            the object to compare
     * @param o2
     *            the object to compare to
     * @return the Comparable.compareTo() return code or 0 if an encoding error was caught.
     * @see Comparable
     */
    @Override
    public int compare(final Object o1, final Object o2) {

        int compareCode = 0;

        try {
            @SuppressWarnings("unchecked") // May fail with CCE if encode returns something that is not Comparable
            // However this was always the case.
            final Comparable> s1 = (Comparable>) this.stringEncoder.encode(o1);
            final Comparable s2 = (Comparable) this.stringEncoder.encode(o2);
            compareCode = s1.compareTo(s2);
        } catch (final EncoderException ee) {
            compareCode = 0;
        }
        return compareCode;
    }

}