State

In State pattern a class behavior changes based on its state. This type of design pattern comes under behavior pattern.

In State pattern, we create objects which represent various states and a context object whose behavior varies as its state object changes.



State in Java recognizable by behavioral methods which changes its behavior depending on the instance's state which can be controlled externally

• javax.faces.lifecycle.LifeCycle#execute() (controlled by FacesServlet, the behavior is dependent on current phase (state) of JSF lifecycle)

public interface State {
   public void doAction(Context context);
}

public class StartState implements State {

   public void doAction(Context context) {
      System.out.println("Player is in start state");
      context.setState(this);	
   }

   public String toString(){
      return "Start State";
   }
}

public class StopState implements State {

   public void doAction(Context context) {
      System.out.println("Player is in stop state");
      context.setState(this);	
   }

   public String toString(){
      return "Stop State";
   }
}

public class Context {
   private State state;

   public Context(){
      state = null;
   }

   public void setState(State state){
      this.state = state;		
   }

   public State getState(){
      return state;
   }
}

public class StatePatternDemo {
   public static void main(String[] args) {
      Context context = new Context();

      StartState startState = new StartState();
      startState.doAction(context);

      System.out.println(context.getState().toString());

      StopState stopState = new StopState();
      stopState.doAction(context);

      System.out.println(context.getState().toString());
   }
}