加密解密基础问题：字节数组和(16进制)字符串的相互转换（转）

    public byte[] getBytes(Charset charset) {
        if (charset == null) throw new NullPointerException();
        return StringCoding.encode(charset, value, 0, value.length);
    }

    /**
     * Encodes this {@code String} into a sequence of bytes using the
     * platform's default charset, storing the result into a new byte array.
     *
     * @return  The resultant byte array
     *
     * @since      JDK1.1
     */
    public byte[] getBytes() {
        return StringCoding.encode(value, 0, value.length);
    }

     /**
     * Constructs a new {@code String} by decoding the specified array of bytes
     * using the platform's default charset.  The length of the new {@code
     * String} is a function of the charset, and hence may not be equal to the
     * length of the byte array.
     *
     * <p> The behavior of this constructor when the given bytes are not valid
     * in the default charset is unspecified.  The {@link
     * java.nio.charset.CharsetDecoder} class should be used when more control
     * over the decoding process is required.*/
    public String(byte bytes[]) {
        this(bytes, 0, bytes.length);
    }

   /**
     * Constructs a new {@code String} by decoding the specified array of
     * bytes using the specified {@linkplain java.nio.charset.Charset charset}.
     * The length of the new {@code String} is a function of the charset, and
     * hence may not be equal to the length of the byte array.
     *
     * <p> This method always replaces malformed-input and unmappable-character
     * sequences with this charset's default replacement string.  The {@link
     * java.nio.charset.CharsetDecoder} class should be used when more control
     * over the decoding process is required.*/
    public String(byte bytes[], Charset charset) {
        this(bytes, 0, bytes.length, charset);
    }

public class HexUtil {
    private static final char[] DIGITS = {
            '0', '1', '2', '3', '4', '5', '6', '7',
            '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
    };

    public static String encodeToString(byte[] bytes) {
        char[] encodedChars = encode(bytes);
        return new String(encodedChars);
    }

    public static char[] encode(byte[] data) {
        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++] = DIGITS[(0xF0 & data[i]) >>> 4];
            out[j++] = DIGITS[0x0F & data[i]];
        }
        return out;
    }

    /**
     * Converts the specified Hex-encoded String into a raw byte array.  This is a
     * convenience method that merely delegates to {@link #decode(char[])} using the
     * argument's hex.toCharArray() value.
     *
     * @param hex a Hex-encoded String.
     * @return A byte array containing binary data decoded from the supplied String's char array.
     */
    public static byte[] decode(String hex) {
        return decode(hex.toCharArray());
    }
    /**
     * Converts an array of characters representing hexidecimal 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 hexidecimal digits
     * @return A byte array containing binary data decoded from
     *         the supplied char array.
     * @throws IllegalArgumentException if an odd number or illegal of characters
     *                                  is supplied
     */
    public static byte[] decode(char[] data) throws IllegalArgumentException {
        int len = data.length;
        if ((len & 0x01) != 0) {
            throw new IllegalArgumentException("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;
    }
    protected static int toDigit(char ch, int index) throws IllegalArgumentException {
        int digit = Character.digit(ch, 16);
        if (digit == -1) {
            throw new IllegalArgumentException("Illegal hexadecimal charcter " + ch + " at index " + index);
        }
        return digit;
    }

public class EncodeTest {
    public static void main(String[] args){
        String str = "???hello/sasewredfdd>>>. Hello 世界！"; 
        System.out.println("str.getBytes()=" + str.getBytes());
        System.out.println("Base64=" + Base64.encodeToString(str.getBytes()));
        
        String hexStr = HexUtil.encodeToString(str.getBytes());    //str.getBytes(Charset.forName("utf-8"));
        
        System.out.println("hexStr=" + hexStr);
        String orignalStr = new String(str.getBytes());     //new String(str.getBytes(), Charset.forName("utf-8"));
        System.out.println("orignalStr=" + orignalStr);
        String str2 = new String(HexUtil.decode(hexStr));
        System.out.println("str2=" + str2);
        System.out.println(str.equals(str2));
        
        String sha = new SimpleHash("sha-256", str, "11d23ccf28fc1e8cbab8fea97f101fc1d", 2).toString();
        System.out.println("sha=" + sha);
    }
}

str.getBytes()=[B@19e0bfd
Base64=Pz8/aGVsbG8vc2FzZXdyZWRmZGQ+Pj4uIEhlbGxvIOS4lueVjO+8gQ==
hexStr=3f3f3f68656c6c6f2f73617365777265646664643e3e3e2e2048656c6c6f20e4b896e7958cefbc81
orignalStr=???hello/sasewredfdd>>>. Hello 世界！
str2=???hello/sasewredfdd>>>. Hello 世界！
true
sha=37a9715fecb5e2f9812d4a02570636e3d5fe476fc67ac34bc824d6a8f835635d