import java.util.Scanner;

class GoodAnswer{
    public static void main(String[] args) {
       char answer = ' ';
       boolean done = false;
       boolean goodAnswer = false;
       
       Scanner myScanner = new Scanner(System.in);
       
       while (!done) {
           // do something like play a game
           System.out.printf("******************\n");
           System.out.printf("* Playing a game *\n");
           System.out.printf("******************\n\n");
           
           goodAnswer = false;
           
           while (!goodAnswer) {
               System.out.print("Do you want to play again? (y-n)=> ");
               answer = myScanner.next().charAt(0);
               System.out.println();

               if (answer == 'n' || answer == 'N') {
                   done = true;
                   goodAnswer = true;
               }
               
               if (answer == 'y' || answer == 'Y') {
                   goodAnswer = true;
               }
               
               if (!goodAnswer) {
                   System.out.printf("%c is invalid, answer y or n \n",answer);
               }
               
           }
           
       }
    }

}