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Commons Codec example source code file (Hex.java)

This example Commons Codec source code file (Hex.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons Codec tags/keywords

classcastexception, d, decoderexception, decoderexception, default_charset_name, digits_lower, digits_upper, hex, hex, io, object, object, string, string, unsupportedencodingexception

The Commons Codec Hex.java source code

/*
 * 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.binary;

import java.io.UnsupportedEncodingException;

import org.apache.commons.codec.BinaryDecoder;
import org.apache.commons.codec.BinaryEncoder;
import org.apache.commons.codec.CharEncoding;
import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.EncoderException;

/**
 * Hex encoder and decoder. The charset used for certain operation can be set, the default is set in
 * {@link #DEFAULT_CHARSET_NAME}
 * 
 * @since 1.1
 * @author Apache Software Foundation
 * @version $Id: Hex.java 801639 2009-08-06 13:15:10Z niallp $
 */
public class Hex implements BinaryEncoder, BinaryDecoder {

    /**
     * Default charset name is {@link CharEncoding#UTF_8}
     */
    public static final String DEFAULT_CHARSET_NAME = CharEncoding.UTF_8;

    /**
     * Used to build output as Hex
     */
    private static final char[] DIGITS_LOWER = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};

    /**
     * Used to build output as Hex
     */
    private static final char[] DIGITS_UPPER = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};

    /**
     * Converts an array of characters representing hexadecimal values into an array of bytes of those same values. The
     * returned array will be half the length of the passed array, as it takes two characters to represent any given
     * byte. An exception is thrown if the passed char array has an odd number of elements.
     * 
     * @param data
     *            An array of characters containing hexadecimal digits
     * @return A byte array containing binary data decoded from the supplied char array.
     * @throws DecoderException
     *             Thrown if an odd number or illegal of characters is supplied
     */
    public static byte[] decodeHex(char[] data) throws DecoderException {

        int len = data.length;

        if ((len & 0x01) != 0) {
            throw new DecoderException("Odd number of characters.");
        }

        byte[] out = new byte[len >> 1];

        // two characters form the hex value.
        for (int i = 0, j = 0; j < len; i++) {
            int f = toDigit(data[j], j) << 4;
            j++;
            f = f | toDigit(data[j], j);
            j++;
            out[i] = (byte) (f & 0xFF);
        }

        return out;
    }

    /**
     * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
     * The returned array will be double the length of the passed array, as it takes two characters to represent any
     * given byte.
     * 
     * @param data
     *            a byte[] to convert to Hex characters
     * @return A char[] containing hexadecimal characters
     */
    public static char[] encodeHex(byte[] data) {
        return encodeHex(data, true);
    }

    /**
     * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
     * The returned array will be double the length of the passed array, as it takes two characters to represent any
     * given byte.
     * 
     * @param data
     *            a byte[] to convert to Hex characters
     * @param toLowerCase
     *            <code>true converts to lowercase, false to uppercase
     * @return A char[] containing hexadecimal characters
     * @since 1.4
     */
    public static char[] encodeHex(byte[] data, boolean toLowerCase) {
        return encodeHex(data, toLowerCase ? DIGITS_LOWER : DIGITS_UPPER);
    }

    /**
     * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
     * The returned array will be double the length of the passed array, as it takes two characters to represent any
     * given byte.
     * 
     * @param data
     *            a byte[] to convert to Hex characters
     * @param toDigits
     *            the output alphabet
     * @return A char[] containing hexadecimal characters
     * @since 1.4
     */
    protected static char[] encodeHex(byte[] data, char[] toDigits) {
        int l = data.length;
        char[] out = new char[l << 1];
        // two characters form the hex value.
        for (int i = 0, j = 0; i < l; i++) {
            out[j++] = toDigits[(0xF0 & data[i]) >>> 4];
            out[j++] = toDigits[0x0F & data[i]];
        }
        return out;
    }

    /**
     * Converts an array of bytes into a String representing the hexadecimal values of each byte in order. The returned
     * String will be double the length of the passed array, as it takes two characters to represent any given byte.
     * 
     * @param data
     *            a byte[] to convert to Hex characters
     * @return A String containing hexadecimal characters
     * @since 1.4
     */
    public static String encodeHexString(byte[] data) {
        return new String(encodeHex(data));
    }

    /**
     * Converts a hexadecimal character to an integer.
     * 
     * @param ch
     *            A character to convert to an integer digit
     * @param index
     *            The index of the character in the source
     * @return An integer
     * @throws DecoderException
     *             Thrown if ch is an illegal hex character
     */
    protected static int toDigit(char ch, int index) throws DecoderException {
        int digit = Character.digit(ch, 16);
        if (digit == -1) {
            throw new DecoderException("Illegal hexadecimal charcter " + ch + " at index " + index);
        }
        return digit;
    }

    private final String charsetName;

    /**
     * Creates a new codec with the default charset name {@link #DEFAULT_CHARSET_NAME}
     */
    public Hex() {
        // use default encoding
        this.charsetName = DEFAULT_CHARSET_NAME;
    }

    /**
     * Creates a new codec with the given charset name.
     * 
     * @param csName
     *            the charset name.
     * @since 1.4
     */
    public Hex(String csName) {
        this.charsetName = csName;
    }

    /**
     * Converts an array of character bytes representing hexadecimal values into an array of bytes of those same values.
     * The returned array will be half the length of the passed array, as it takes two characters to represent any given
     * byte. An exception is thrown if the passed char array has an odd number of elements.
     * 
     * @param array
     *            An array of character bytes containing hexadecimal digits
     * @return A byte array containing binary data decoded from the supplied byte array (representing characters).
     * @throws DecoderException
     *             Thrown if an odd number of characters is supplied to this function
     * @see #decodeHex(char[])
     */
    public byte[] decode(byte[] array) throws DecoderException {
        try {
            return decodeHex(new String(array, getCharsetName()).toCharArray());
        } catch (UnsupportedEncodingException e) {
            throw new DecoderException(e.getMessage(), e);
        }
    }

    /**
     * Converts a String or an array of character bytes representing hexadecimal values into an array of bytes of those
     * same values. The returned array will be half the length of the passed String or array, as it takes two characters
     * to represent any given byte. An exception is thrown if the passed char array has an odd number of elements.
     * 
     * @param object
     *            A String or, an array of character bytes containing hexadecimal digits
     * @return A byte array containing binary data decoded from the supplied byte array (representing characters).
     * @throws DecoderException
     *             Thrown if an odd number of characters is supplied to this function or the object is not a String or
     *             char[]
     * @see #decodeHex(char[])
     */
    public Object decode(Object object) throws DecoderException {
        try {
            char[] charArray = object instanceof String ? ((String) object).toCharArray() : (char[]) object;
            return decodeHex(charArray);
        } catch (ClassCastException e) {
            throw new DecoderException(e.getMessage(), e);
        }
    }

    /**
     * Converts an array of bytes into an array of bytes for the characters representing the hexadecimal values of each
     * byte in order. The returned array will be double the length of the passed array, as it takes two characters to
     * represent any given byte.
     * <p>
     * The conversion from hexadecimal characters to the returned bytes is performed with the charset named by
     * {@link #getCharsetName()}.
     * </p>
     * 
     * @param array
     *            a byte[] to convert to Hex characters
     * @return A byte[] containing the bytes of the hexadecimal characters
     * @throws IllegalStateException
     *             if the charsetName is invalid. This API throws {@link IllegalStateException} instead of
     *             {@link UnsupportedEncodingException} for backward compatibility.
     * @see #encodeHex(byte[])
     */
    public byte[] encode(byte[] array) {
        return StringUtils.getBytesUnchecked(encodeHexString(array), getCharsetName());
    }

    /**
     * Converts a String or an array of bytes into an array of characters representing the hexadecimal values of each
     * byte in order. The returned array will be double the length of the passed String or array, as it takes two
     * characters to represent any given byte.
     * <p>
     * The conversion from hexadecimal characters to bytes to be encoded to performed with the charset named by
     * {@link #getCharsetName()}.
     * </p>
     * 
     * @param object
     *            a String, or byte[] to convert to Hex characters
     * @return A char[] containing hexadecimal characters
     * @throws EncoderException
     *             Thrown if the given object is not a String or byte[]
     * @see #encodeHex(byte[])
     */
    public Object encode(Object object) throws EncoderException {
        try {
            byte[] byteArray = object instanceof String ? ((String) object).getBytes(getCharsetName()) : (byte[]) object;
            return encodeHex(byteArray);
        } catch (ClassCastException e) {
            throw new EncoderException(e.getMessage(), e);
        } catch (UnsupportedEncodingException e) {
            throw new EncoderException(e.getMessage(), e);
        }
    }

    /**
     * Gets the charset name.
     * 
     * @return the charset name.
     * @since 1.4
     */
    public String getCharsetName() {
        return this.charsetName;
    }

    /**
     * Returns a string representation of the object, which includes the charset name.
     * 
     * @return a string representation of the object.
     */
    public String toString() {
        return super.toString() + "[charsetName=" + this.charsetName + "]";
    }
}

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