Hello guys,

DOES ANYBODY KNOW HOW TO USE PVECTOR IN ECLIPSE IN A CLASS?
I just try to build an app with some strings but i dont have any look creating it in eclipse using pvector, here is the code:

the main mathod:

////////////////////
import processing.core.*;

public class main extends PApplet{
   
    public static void main(String args[])  {
        PApplet.main(new String[] { "main" });
    }
   
    PSpring spring;
    PVector startpos = new PVector(0,0);

   
    public void setup(){
        spring = new PSpring(startpos, 700.0f, 10.0f, 0.7f, 0.7f, this);
        //println(pp);
       
    }
   
    public void draw(){
        spring.update(mouseX, mouseY);
       
    }

}
//////////////

the spring class :



import processing.core.PApplet;
import processing.core.PVector;


public class PSpring{
    //Vars
   
     PVector velocity;
     PVector position;
    float mass;
    float radii;
    float stiffness;
    float damping;
    PApplet p;
   
    public PSpring(PVector position_, float mass_, float radii_, float stiffness_, float damping_,PApplet pp) {
        // TODO Auto-generated constructor stub
        position = position_;
        mass = mass_;
        radii = radii_;
        stiffness = stiffness_;
        damping = damping_;
        p = pp;
    }
   
    public void update(float tx,float ty){
        //update pos
         PVector target = new PVector(tx,ty);
         PVector force = (PVector.sub(target, position));
        force =  PVector.mult(force, stiffness);
         PVector acceleration = PVector.div(force, mass);
        velocity = PVector.add(velocity, acceleration);
        velocity.mult(damping);
        position = PVector.add(position,velocity);
    }

}



this doesnt work.. and what i get is:

Exception in thread "Animation Thread" java.lang.NullPointerException
    at processing.core.PVector.add(Unknown Source)
    at processing.core.PVector.add(Unknown Source)
    at PSpring.update(PSpring.java:32)
    at main.draw(main.java:20)
    at processing.core.PApplet.handleDraw(Unknown Source)
    at processing.core.PApplet.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:662)


hope anybody has an idea