Arduino and Processing communication

  import processing.serial.*;
  Serial port;
  
  String data = "";
  String Power = "No Connect !";
  int index_Power = 0;
  int index_Alarme =0;
  
  void setup()
  {
   background(0,0,0);
   size(600,400);
   port = new Serial(this, "COM11", 57600);
   port.bufferUntil('.'); 
  }   
  
  void draw()
  {
  Etat_Arduino(Power,112,103); //print : "ERROR !" instead of "OK !"
  fill(46, 209, 2);
  text(Power, 70, 320);   //print : "1"
  }
  
  void serialEvent (Serial port)
  {
  data = port.readStringUntil('.');
  data = data.substring(0, data.length() - 1);
  index_Power = data.indexOf(",");
  Power = data.substring(0, index_Power );
  }
  
  void Etat_Arduino(String V,int X,int Y)
  {
  if (V == "1")
  {
  text("OK !",X,Y);   
  }
  else
  {
  text("ERROR !",X,Y);
  }
  }

I would also like to change the variable that the program of the arduino send me, for example, it sent me "Power = 1" and I want to "Power = 0" so I sent it 0, and I will add another variables, how can I do for the arduino to receive. and processing sent it?