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The Apache Commons Codec component contains encoders and decoders for various formats such as Base16, Base32, Base64, digest, and Hexadecimal. In addition to these widely used encoders and decoders, the codec package also maintains a collection of phonetic encoding utilities. This is a port for GWT, which enables program, to use Apache Commons Codec also in the frontend compiled by the gwt compiler to java-script.

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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.language;

import org.apache.commons.codec.EncoderException;
import org.apache.commons.codec.StringEncoder;

/**
 * Utility methods for {@link Soundex} and {@link RefinedSoundex} classes.
 *
 * This class is immutable and thread-safe.
 *
 * @since 1.3
 */
final class SoundexUtils {

    /**
     * Cleans up the input string before Soundex processing by only returning
     * upper case letters.
     *
     * @param str
     *                  The String to clean.
     * @return A clean String.
     */
    static String clean(final String str) {
        if (str == null || str.length() == 0) {
            return str;
        }
        final int len = str.length();
        final char[] chars = new char[len];
        int count = 0;
        for (int i = 0; i < len; i++) {
            if (Character.isLetter(str.charAt(i))) {
                chars[count++] = str.charAt(i);
            }
        }
        if (count == len) {
            return str.toUpperCase(java.util.Locale.ENGLISH);
        }
        return new String(chars, 0, count).toUpperCase(java.util.Locale.ENGLISH);
    }

    /**
     * Encodes the Strings and returns the number of characters in the two
     * encoded Strings that are the same.
     * 
     * For Soundex, this return value ranges from 0 through 4: 0 indicates
     * little or no similarity, and 4 indicates strong similarity or identical
     * values.
     * For refined Soundex, the return value can be greater than 4.
     * 
     *
     * @param encoder
     *                  The encoder to use to encode the Strings.
     * @param s1
     *                  A String that will be encoded and compared.
     * @param s2
     *                  A String that will be encoded and compared.
     * @return The number of characters in the two Soundex encoded Strings that
     *             are the same.
     *
     * @see #differenceEncoded(String,String)
     * @see 
     *          MS T-SQL DIFFERENCE
     *
     * @throws EncoderException
     *                  if an error occurs encoding one of the strings
     */
    static int difference(final StringEncoder encoder, final String s1, final String s2) throws EncoderException {
        return differenceEncoded(encoder.encode(s1), encoder.encode(s2));
    }

    /**
     * Returns the number of characters in the two Soundex encoded Strings that
     * are the same.
     * 
     * For Soundex, this return value ranges from 0 through 4: 0 indicates
     * little or no similarity, and 4 indicates strong similarity or identical
     * values.
     * For refined Soundex, the return value can be greater than 4.
     * 
     *
     * @param es1
     *                  An encoded String.
     * @param es2
     *                  An encoded String.
     * @return The number of characters in the two Soundex encoded Strings that
     *             are the same.
     *
     * @see 
     *          MS T-SQL DIFFERENCE
     */
    static int differenceEncoded(final String es1, final String es2) {

        if (es1 == null || es2 == null) {
            return 0;
        }
        final int lengthToMatch = Math.min(es1.length(), es2.length());
        int diff = 0;
        for (int i = 0; i < lengthToMatch; i++) {
            if (es1.charAt(i) == es2.charAt(i)) {
                diff++;
            }
        }
        return diff;
    }

}