Hello, everybody.
First I'm sorry if i posted it wrong, cause i do not know it better, but i will learn.
Second: I got an arduino board with a potentiometer on it and i wanna send this data to processing. Arduino works good but processing always crying with the NullPointerException. I've looked in other forums for it, but it isn't the same problem like mine (they sad systemfont Monaco is off, but ithat isn't my problem).
So here is the arduino code:

int ledPin1 = 13;


int potPin = 2;

int val = 0;

void setup()
{
Serial.begin(9600);
pinMode(ledPin1, OUTPUT);


}

void loop()
{
val = analogRead(potPin)/4;
Serial.println(val);
delay(20);


val = analogRead(potPin);
digitalWrite(ledPin1, HIGH);
delay(val);
digitalWrite(ledPin1, LOW);
delay(val);
}

and processing:
import processing.serial.*;
int potent = 0;
int linefeed = 10;
int ret = 13;
Serial port;





void setup(){
size(800,800);

port = new Serial(this, Serial.list()[Serial.list().length-1], 9600);
}
void draw(){
background(255);
if(port.available() > 0) {
String data = port.readStringUntil(linefeed);
println("String: " + data);

potent = int(data);
}
println(potent);
drawEllipse(potent, potent/10);
}



void drawEllipse(int sizeTemp, int flacker){
smooth();
//noFill();
fill(0);
strokeWeight(1);
ellipse(width/2,height/2, random(sizeTemp-flacker,sizeTemp), random(sizeTemp-flacker, sizeTemp));
}

and know processing is doing:
Stable Library
=========================================
Native lib Version = RXTX-2.1-7
Java lib Version   = RXTX-2.1-7
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
String: null

Exception in thread "Animation Thread" java.lang.NullPointerException
     at processing.core.PApplet.parseInt(PApplet.java:5617)
     at processing.core.PApplet.parseInt(PApplet.java:5608)
     at potent.draw(potent.java:40)
     at processing.core.PApplet.handleDraw(PApplet.java:1423)
     at processing.core.PApplet.run(PApplet.java:1328)
     at java.lang.Thread.run(Unknown Source)

and potent = int(data); is always marked.

I'm sorry for the bad english, but it will getting better next time

Thank you for your answer, now there is no error anymore, but the ellipse is not drawn, the sring i got is the same like arduino shows, but the interger, i need to draw, is always 0. Now my question is, how can i get  the nessesary data? I've tried to convert but it didn't work

Heres the Code:

import processing.serial.*;
int potent = 0;
int linefeed = 10;
int ret = 13;
String myString = null;
Serial port;





void setup(){
 size(800,800);
 //MouseX durch Arduino Werte ersetzen

 port = new Serial(this, Serial.list()[0], 9600);
 port.clear();
 myString = port.readStringUntil(linefeed);
 myString = null;
}
void draw(){
 background(255);
 while(port.available() > 0) {
   myString = port.readStringUntil(linefeed);
   if (myString != null){
     println(myString);
   }
   String myString = "23";
   int potent = Integer.parseInt(myString);
 }
 println(potent);
 drawEllipse(potent, potent/10);
}



void drawEllipse(int sizeTemp, int flacker){
 smooth();
 //noFill();
 fill(0);
 strokeWeight(1);
 ellipse(width/2,height/2, random(sizeTemp-flacker,sizeTemp), random(sizeTemp-flacker, sizeTemp));
}