In the act method of your active world class, if the list returned from using the 'getObjects(Enemy.class)' is empty then do what you need to do to set up the next level (presuming that 'Enemy' is the name of your class that your enemies are created in).
In the act method of your active world class, if the list returned from using the 'getObjects(Enemy.class)' is empty then do what you need to do to set up the next level (presuming that 'Enemy' is the name of your class that your enemies are created in).