import processing.serial.*;

Serial port;  // Create object from Serial class
int sensorValue;  // Data received from the serial port

void setup() {
  size(600, 600);
  noStroke();
  // List all the available serial ports in the output pane.
  // I use port #9.
  println(Serial.list());

  // Make sure to open port 9 the same speed Arduino is using (9600bps)
  port = new Serial(this, Serial.list()[9], 9600);
}

void draw() {
  if (0 < port.available()) {   // If data is available to read,
    sensorValue = port.read();  // read it and store it in val
  }
  background(0);              // Clear background
  line(40,sensorValue/.4,560,sensorValue/.4);  // Draw a line with Y value according to sensor
  stroke(0, 100, 139);  // Set color
  strokeCap(SQUARE);  // Set cap style
  strokeWeight(400/(sensorValue+1));       // Set weight with the value reading
}