Screen Wraping

int w=getWorld().getWidth();
int h=getWorld().getHeight()
setLocation((getX()+w)%w, ((getY()+h)%h);

import greenfoot.*;  // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)

/**
 * Write a description of class Rocket here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class Rocket extends Actor
{
    /**
     * Act - do whatever the Rocket wants to do. This method is called whenever
     * the 'Act' or 'Run' button gets pressed in the environment.
     */
    public void act() 
    
    {
        move(4);
        int w=getWorld().getWidth();
        int h=getWorld().getHeight();
        setLocation((getX()+w)%w, ((getY()+h)%h));
 
        if (Greenfoot.isKeyDown("left"))
        {
            turn(-3);
        }
        if (Greenfoot.isKeyDown("right"))
        {
            turn(3);
        }
         //if (Greenfoot.isKeyDown("down"))
        {
            setLocation(getX(), getY()+3);
        }
          //if (Greenfoot.isKeyDown("up"))
        {
            setLocation(getX(), getY()-3);
        }
        Actor Pear;
        Pear = getOneObjectAtOffset(0, 0, Pear.class);
        if (Pear != null)
        {
            World Space;
            Space = getWorld();
            Space.removeObject(Pear);
        }
    
    }    
}