Some Examples

Objectives

1. Look at some additional application

Notes

• Ask the user for a y to stop. Accept either a y or a Y

• import java.util.Scanner;
  
  class CharReader{
      public static void main(String[] args) {
         char answer;
         boolean done = false;
         
         Scanner myScanner = new Scanner(System.in);
         
         
         while(!done) {
             System.out.print("Enter a letter (y-n) => ");
             answer = myScanner.next().charAt(0);
             System.out.println();
             
             System.out.printf("You entered a '%c'\n",answer);
             if(answer == 'y' || answer == 'Y') {
                done = true;
             }
         }
      }
  } 

• Notes:
  • scanner.next() will read the next character or string.
    • .charAt(0) will return the first character.
    • More on this later.
  • Note this is a flag controlled loop
    • done is called a flag.
    • Notice how the loop read "While not done"
• Change this so that it only accept a y or an n.

  import java.util.Scanner;
  
  class CharReader{
      public static void main(String[] args) {
         char answer = ' ';
         boolean done = false;
         boolean goodAnswer = false;
  
         Scanner myScanner = new Scanner(System.in);
  
         while(!done) {
  
             System.out.printf("******************\n");
             System.out.printf("* Playing a game *\n");
             System.out.printf("******************\n\n");
  
             // do something like play a game
  
             goodAnswer = false;
             while (!goodAnswer) {
  
                 System.out.println("Do you want to play again?");
                 System.out.print("Enter a letter (y-n) => ");
                 answer = myScanner.next().charAt(0);
                 System.out.println();
  
                 if(answer == 'y' || answer == 'Y') {
                    goodAnswer = true;
                 }
  
                 if (answer == 'n' || answer == 'N') {
                     done = true;
                     goodAnswer = true;
                 }
  
                 if (! goodAnswer) {
                     System.out.printf("You entered a %c, that is not y-n\n",answer);
                 }
              }
              System.out.printf("Got a good answer of %c\n", answer);
         }
  
      }
  }
       

• See getGoodAnswer.java