When I was going to create another state I had an error. This is my code:

   public static final int play2 = 3;

and

public Game(String gamename){

      this.addState(new mission(play2));
   }

and

public void initStatesList(GameContainer gc) throws SlickException{
      this.getState(play2).init(gc, this);

   }

I have an error in the addState. above the above code. I don't know where is the problem. But if you want the whole code it is here: package javagame;

import org.newdawn.slick.*;

import org.newdawn.slick.state.*;

public class Game extends StateBasedGame{

   public static final String gamename = "NET FRONT";
   public static final int menu = 0;
   public static final int play = 1;
   public static final int train = 2;
   public static final int play2 = 3;

   public Game(String gamename){
      super(gamename);
      this.addState(new Menu(menu));
      this.addState(new Play(play));
      this.addState(new train(train));
      this.addState(new mission(play2));
   }

   public void initStatesList(GameContainer gc) throws SlickException{
      this.getState(menu).init(gc, this);
      this.getState(play).init(gc, this);
      this.getState(train).init(gc, this);
      this.enterState(menu);
      this.getState(play2).init(gc, this);

   }

   public static void main(String[] args) {

      try{
          AppGameContainer app =new AppGameContainer(new Game(gamename));
          app.setDisplayMode(1500, 1000, false);
          app.start();
      }catch(SlickException e){
         e.printStackTrace();
      }
   }

}
//SYSTEM NETWORKS(C) 2012 NET FRONT