Sending a program back to the beginning..

Question

I dont think the topic explains it right, but I need to be able to go back to the beginning of the block again if it loops. I'll just post the code as its probably easier to see what I want to do that way... :)
public class ABCInput
     public static void main(String []args) throws Exception
          char letterInput;
          System.out.println("Type A, B, C, or Q.");
          letterInput = (char)System.in.read();
          System.in.read();
          System.in.read();
          while (letterInput != 'A' || letterInput != 'B' || letterInput != 'C' || letterInput != 'Q')
               System.out.println("Incorrect, try again.");
               letterInput = (char)System.in.read();
               System.in.read();
               System.in.read();
          while (letterInput == 'A' || letterInput == 'B' || letterInput == 'C')
               System.out.println("Good Job.");
               System.out.println("Add another character");
               letterInput = (char)System.in.read();
               System.in.read();
               System.in.read();               
          if (letterInput == 'Q')
               System.out.println("Exiting Application!");
               System.exit(0);     
}

Answer 1

Instead of putting little loops around each case, put a large one around everythingchar letterInput;
System.out.println("Type A, B, C, or Q.");          
letterInput = (char)System.in.read();
while (letterInput!='Q') {
   If (letterInput=='A' || letterInput == 'B' || letterInput == 'C') {
       //blah
  } else {
    System.out.println("Incorrect, try again.");
  letterInput = (char)System.in.read();
System.exit(0);