Convert a base16 string into a byte array. : Byte Array « File « Java Tutorial

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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.    
 */

/**
 * Base 16 encoder.
 *
 * @author Marc Prud'hommeaux
 * @nojavadoc
 */
 class Base16Encoder {

    private final static char[] HEX = new char[]{
        '0', '1', '2', '3', '4', '5', '6', '7',
        '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

    /**
     * Convert bytes to a base16 string.
     */
    public static String encode(byte[] byteArray) {
        StringBuffer hexBuffer = new StringBuffer(byteArray.length * 2);
        for (int i = 0; i < byteArray.length; i++)
            for (int j = 1; j >= 0; j--)
                hexBuffer.append(HEX[(byteArray[i] >> (j * 4)) & 0xF]);
        return hexBuffer.toString();
    }

    /**
     * Convert a base16 string into a byte array.
     */
    public static byte[] decode(String s) {
        int len = s.length();
        byte[] r = new byte[len / 2];
        for (int i = 0; i < r.length; i++) {
            int digit1 = s.charAt(i * 2), digit2 = s.charAt(i * 2 + 1);
            if (digit1 >= '0' && digit1 <= '9')
                digit1 -= '0';
            else if (digit1 >= 'A' && digit1 <= 'F')
                digit1 -= 'A' - 10;
            if (digit2 >= '0' && digit2 <= '9')
                digit2 -= '0';
            else if (digit2 >= 'A' && digit2 <= 'F')
                digit2 -= 'A' - 10;

            r[i] = (byte) ((digit1 << 4) + digit2);
        }
        return r;
    }
}