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

/**
 * The ball of the game. It moves and bounces off the walls and the paddle.
 * 
 * @author mik
 * @version 1.0
 */
public class Ball extends Actor
{
    private int deltaX;         // x movement speed
    private int deltaY;         // y movement speed
    private int count = 2;
    
    private boolean stuck = true;   // stuck to paddle
    private int counter;
    private int counter1;
    
    public Ball()
    {
        counter = 0;
        counter1 = 30;
    }
    
    /**
     * Act. Move if we're not stuck.
     */
    public void act() 
    {
        if (!stuck) 
        {
            move();
            checkOut();
            checkBlock();
            if(counter1 <= 0)
            {
                getWorld().addObject(new YouLose(),228, 234);
                getWorld().removeObject(this);
            }
        }
    }
    
    /**
     * Move the ball. Then check what we've hit.
     */
    public void move()
    {
        setLocation (getX() + deltaX, getY() + deltaY);
        checkPaddle();
        checkWalls();
    }
    
    /**
     * Check whether we've hit one of the three walls. Reverse direction if necessary.
     */
    private void checkWalls()
    {
        if (getX() == 0 || getX() == getWorld().getWidth()-1) {
            deltaX = -deltaX;
        }
        if (getY() == 0) {
            deltaY = -deltaY;
        }
    }
    
    private void checkBlock()
    {
        Actor block = getOneIntersectingObject(Block.class);
        if(block != null)
        {
            getWorld().removeObject(block);
            deltaY=-deltaY;
            counter++;
            Board myBoard = (Board) getWorld();
            myBoard.score();
            if(counter >= 18)
            {
                getWorld().addObject(new YouWon(), 228, 234);
                getWorld().removeObject(this);
            }
        }
    }
    
    /**
     * Check whether we're out (bottom of screen).
     */
    private void checkOut()
    {
        if (getY() == getWorld().getHeight()-1) {
            ((Board) getWorld()).ballIsOut();
            getWorld().removeObject(this);
        }
    }
    
    private void checkPaddle()
    {
        Actor paddle = getOneIntersectingObject(Paddle.class);
        if (paddle != null) {
            deltaY = -deltaY;
            int offset = getX() - paddle.getX();
            deltaX = deltaX + (offset/10);
            if (deltaX > 7) {
                deltaX = 7;
                counter1 = counter1--;
            }
            if (deltaX < -7) {
                deltaX = -7;
                counter1 = counter1--;
            }
        }            
    }
    
    /**
     * Move the ball a given distance sideways.
     */
    public void move(int dist)
    {
        setLocation (getX() + dist, getY());
    }
    
    /**
     * Release the ball from the paddle.
     */
    public void release()
    {
        deltaX = Greenfoot.getRandomNumber(11) - 5;
        deltaY = -5;
        stuck = false;
    }
}

java.lang.IllegalStateException: Actor not in world. An attempt was made to use the actor's location while it is not in the world. Either it has not yet been inserted, or it has been removed.
	at greenfoot.Actor.failIfNotInWorld(Actor.java:711)
	at greenfoot.Actor.getOneIntersectingObject(Actor.java:958)
	at Ball.checkBlock(Ball.java:68)
	at Ball.act(Ball.java:34)
	at greenfoot.core.Simulation.actActor(Simulation.java:604)
	at greenfoot.core.Simulation.runOneLoop(Simulation.java:562)
	at greenfoot.core.Simulation.runContent(Simulation.java:221)
	at greenfoot.core.Simulation.run(Simulation.java:211)

if (getWorld() == null) return;

    /**
     * Throws an exception if the actor is not in a world.
     * 
     * @throws IllegalStateException If not in world.
     */
    private void failIfNotInWorld()
    {
        if(world == null) {
            throw new IllegalStateException(ACTOR_NOT_IN_WORLD);
        }
    }