I'm a new Arduino user, as well as new to Processing. I'm working on an example sketch named Graph, which uses both languages. The sketch involves loading and running a segment using Arduino as follows:

void setup() {
  Serial.begin(9600);
}
void loop() {
  Serial.println(analogRead(A0));
  delay(10);
}
This segment is compiled and uploaded to an Arduino Uno. Next, a segment is written in Processing as follows:

 import processing.serial.*;

 Serial myPort;      
  int xPos = 1;       

  void setup () {
   size(400, 300);       
   println(Serial.list());
   myPort = new Serial(this, Serial.list()[0], 9600);
  myPort.bufferUntil('\n');
   background(0);
  }
  void draw () {
  }
 
 void serialEvent (Serial myPort) {
   String inString = myPort.readStringUntil('\n');
 if (inString != null) {
   inString = trim(inString);
  float inByte = float(inString);
  inByte = map(inByte, 0, 1023, 0, height);
   stroke(127,34,255);
  line(xPos, height, xPos, height - inByte);
   if (xPos >= width) {
  xPos = 0;
  background(0);
  }
  else {
   xPos++;
  }
  }
  }
 
This is then compiled and uploaded to the Arduino, which is already running the Arduino segment.
The problem is that this segment will not compile correctly. The error message I get is
     "Error inside Serial.<init>()"
When the error appears, the line beginning
     myPort=new Serial(this,.......
is highlighted.
Can someone offer suggestions on what I'm doing wrong?