// the Lobster class 'lookForCrab' method
public void lookForCrab()
{ 
    Crab crab = (Crab)getOneObjectAtOffset(0, 0, Crab.class); // this line gives more play area for crab around the lobster
    if (crab == null) return;
    if (crab.isPoweredUp()) // this line ensures the powered-up crab is not eaten by lobster
    {
        getWorld().removeObject(this);
        return;
    }
    getWorld().removeObject(crab);
    Greenfoot.playSound("au.wav");
    Greenfoot.stop();
}

// the Lobster class 'lookForCrab' method
public void lookForCrab()
{ 
    Crab crab = (Crab)getOneIntersectingObject(Crab.class); 
    if (crab == null) return;
    if (crab.isPoweredUp()) // this line ensures the powered-up crab is not eaten by lobster
    {
        getWorld().removeObject(this);
        return;
    }
    if (getObjectAtOffset(0, 0, Crab.class) == null) return;
    getWorld().removeObject(crab);
    Greenfoot.playSound("au.wav");
    Greenfoot.stop();
}

if (getOneObjectAtOffset(0, 0, Crab.class) == null) return;

public void wormPowerUp()
    {
        if (wormPowerUp == true)
        {
            Crab crab = (Crab) getWorld().getObjects(Crab.class).get(0);  
            turnTowards(crab.getX(), crab.getY());  
            move(3);
        }
    }

// add instance field to Crab class
private int wpTimer;
// in act
ifCanSeeWP();
// add methods
private void ifCanSeeWP()
{
    if (canSee(WormPowerUp.class))
    {
        eat(WormPowerUp.class);
        wpTimer = 500;
    }
    if (wormPowered()) wpTimer--;
}

public boolean wormPowered()
{
    return wpTimer > 0;
}

// the 'wormPowerUp' method in your Worm class
private void wormPowerUp()
{
    Crab crab = (Crab)getWorld().getObjects(Crab.class).get(0);
    if (crab != null && crab.wormPowered())
    {
        turnTowards(crab.getX(), crab.getY());
        move(3);
    }
}