code: private final void setFlagValue(byte flagBit, boolean value) {
          if (value) {
              flags = (byte) (getFlags() | flagBit);
          }
          else {
              flags = (byte) (getFlags() & (~flagBit));
          }
      }
docs: Set the boolean 'value' of one of the flags in the FLAGS field of th message.
  
  @param flagBit A byte with a single bit set on, marking the position
  of the required flag.
  @param value true if the required flag is to be set on, otherwise false