code: private static void onDataReceiveCallback(int fileDescriptor, byte[] data) {
  
          // notify event listeners
          if(listeners.containsKey(fileDescriptor)){
              SerialInterruptListener listener = listeners.get(fileDescriptor);
              if(listener != null) {
                  SerialInterruptEvent event = new SerialInterruptEvent(listener, fileDescriptor, data);
                  listener.onDataReceive(event);
              }
          }
  
          //System.out.println("SERIAL PORT [" + fileDescriptor + "] DATA LENGTH = " + data.length + " / " + new String(data));
      }
docs: <p>
  This method is provided as the callback handler for the Pi4J native library to invoke when a
  GPIO interrupt is detected. This method should not be called from any Java consumers. (Thus
  is is marked as a private method.)
  </p>
  
  @param fileDescriptor the serial file descriptor/handle
  //@param data byte array of data received on this event from the serial receive buffer