code: public static byte[] fromHex(String hex) {
  		char[] c = hex.toCharArray();
  		byte[] b = new byte[c.length / 2];
  		for (int i = 0; i < b.length; i ++) {
  			b[i] = (byte) (HEX_DECODE_CHAR[c[i * 2] & 0xFF] * 16 +
  					HEX_DECODE_CHAR[c[i * 2 + 1] & 0xFF]);
  		}
  		return b;
  	}
docs: Decode from hexadecimal