Java Lejos NXT

import lejos.nxt.*;
import lejos.robotics.navigation.*;
public class Roboter{
  private DifferentialPilot dieMotoren;
  private LightSensor derLichtsensor;
  private LCD dasDisplay;
  
  private final static double RADDURCHMESSER = 5.6;
  private final static double RADABSTAND      = 17.3;
  private final static double KORREKTURWINKEL = 10.0;
  private final static int    INTERVALL       = 20;  
                              
  private int schwarz,weiss;                            
  public Roboter(){
    dieMotoren = new DifferentialPilot(RADDURCHMESSER, RADABSTAND, Motor.A, Motor.C);
    derLichtsensor  = new LightSensor(SensorPort.S3);
    dasDisplay = new LCD();
    }
  
  public void kalibrieren()throws InterruptedException{
    int messwert = 0;
    dasDisplay.drawString("-> ENTER <-", 2, 2);
    Button.ENTER.waitForPressAndRelease();
    
    while (!Button.LEFT.isDown()) { 
      dasDisplay.clear();
      dasDisplay.refresh();
      messwert = derLichtsensor.readValue();
      Thread.sleep(25);
      dasDisplay.drawString("Weiss = " + messwert, 0,2);
    }
    
    weiss = messwert;
    
    while (!Button.RIGHT.isDown()) {
    dasDisplay.clear();
    dasDisplay.refresh();
    messwert = derLichtsensor.readValue();
    Thread.sleep(25);
    dasDisplay.drawString("Schwarz = "+messwert,0,2);  
    }
    schwarz = messwert;
    
    dasDisplay.clear();
    dasDisplay.refresh();
    dasDisplay.drawString("Schwarz = "+schwarz,0,1);
    dasDisplay.drawString("Weiss = "+weiss,0,3);
    dasDisplay.drawString("=> ENTER <=",0,5);
    Button.ENTER.waitForPressAndRelease();
    }
    
    public void run()
    { 
   
    }
}