code: public void enterState(int id, Transition leave, Transition enter) {
  		if (leave == null) {
  			leave = new EmptyTransition();
  		}
  		if (enter == null) {
  			enter = new EmptyTransition();
  		}
  		leaveTransition = leave;
  		enterTransition = enter;
  		
  		nextState = getState(id);
  		if (nextState == null) {
  			throw new RuntimeException("No game state registered with the ID: "+id);
  		}
  		
  		leaveTransition.init(currentState, nextState);
  	}
docs: Enter a particular game state with the transitions provided
  
  @param id The ID of the state to enter
  @param leave The transition to use when leaving the current state
  @param enter The transition to use when entering the new state