====== StateManager ======

==== Motivation ====
You want to adopt the [[finite state machine]] pattern because your game has many states and it becoming difficult to maintain. 

==== Description ====
This is the second half of the [[finite state machine]] pattern. This class is the actual proxy for your states. In addition to acting as a proxy for concrete states the state manager facilitates transitioning between different states.

==== Example ====
<code java>
public class StateManager {
    private LinkedList<State> states;
    private State currentState;
    public StateManager() {
        states = new LinkedList<State>();
    }
    public void add(State s) {
        states.add(s);
        if (currentState == null) {
            currentState = s;
            currentState.enter();
        }
    }
    /** Transition to the designated state. */
    public void enter(Object o) {
        for (State s : states) {
            if (s.equals(o)) {
                currentState = s;
                currentState.enter();
            }
        }
    }
    /** Useful if you need to know what state you are currently in. */
    public Object currentState() {
        return currentState;
    }
    public void update(StateBasedGame game, int delta) {
        currentState.update(game, delta);
    }
    public void onCollision(Entity obstacle) {
        currentState.onCollision(obstacle);
    }
    public void render(Graphics g) {
        currentState.render(g);
    }
}
</code>