It'd seem that the method doesn't exist.
You can use the following code for an atWorldEdge method. Replace the 10s as you wish. Generally, people want objects to bounce when the edge of it hits the very borders of the world, so I'd recommend replacing the 10s with half of the size in pixels of your image.
public boolean atWorldEdge()
{
if(getX() < 10 || getX() > getWorld().getWidth() - 10)
return true;
if(getY() < 10 || getY() > getWorld().getHeight() - 10)
return true;
else
return false;
}