code: static void checkSignedByte(final int value, final String msg) {
          if (value < Byte.MIN_VALUE || value > Byte.MAX_VALUE) {
              throw new IllegalArgumentException(msg
                      + " (must be a signed byte): " + value);
          }
      }
docs: Checks that the given value is a signed byte.
  
  @param value
  the value to be checked.
  @param msg
  an message to be used in case of error.