Do-while loop won't loop after switch-case statement

Question

I'm trying to make some code that will ask the user what function they want to complete (such as finding which quadrant on a graph a point is, etc.). But I also want the code to ask the user to reenter a number if it isn't between 1 and 6 inclusive. I tried to do this by creating a do-while loop but for some reason it won't even loop. Any tips on making it shorter/cleaner are well appreciated.

Below is what I am having trouble with:

  int whichMethod;
   do{ 
     whichMethod = scan.nextInt();
     switch(whichMethod){
       case 1:
         System.out.println("Enter x and y values:");
         x = scan.nextDouble();
         y = scan.nextDouble();
         Point p = new Point(x, y);
         System.out.println("Quadrant:"+ p.quadrant());
         break;
       case 2:
         System.out.println("Enter x and y values:");
         x = scan.nextDouble();
         y = scan.nextDouble();
         Point case2p = new Point(x, y);
         case2p.flip();
         System.out.println("Flipped Coordinates" + case2p);
         break;
       case 3:
         System.out.println("Enter x and y values:");
         x = scan.nextDouble();
         y = scan.nextDouble();
         Point case3p = new Point(x, y);

         System.out.println("Enter x and y values for the 2nd Point: ");
         x = scan.nextDouble();
         y = scan.nextDouble();
         Point case3p2 = new Point(x, y);
         System.out.println("Manhattan Distance:"+ 
         case3p.manhattanDistance(case3p2));
         break;
       case 4:
         System.out.println("Enter x and y values:");
         x = scan.nextDouble();
         y = scan.nextDouble();
         Point case4p = new Point(x, y);

         System.out.println("Enter x and y values for the 2nd Point: ");
         x = scan.nextDouble();
         y = scan.nextDouble();
         Point case4p2 = new Point(x, y);
         System.out.println("Are they Vertical?: " + case4p.isVertical(case4p2));
         break;
       case 5:
         System.out.println("Enter x and y values:");
         x = scan.nextDouble();
         y = scan.nextDouble();
         Point case5p = new Point(x, y);

         System.out.println("Enter x and y values for the 2nd Point:");
         x = scan.nextDouble();
         y = scan.nextDouble();
         Point case5p2 = new Point(x, y);
         System.out.println("Slope is: " + case5p.slope(case5p2));
         break;
       case 6:
         System.out.println("Enter x and y values:");
         x = scan.nextDouble();
         y = scan.nextDouble();
         Point case6p = new Point(x, y);

         System.out.println("Enter x and y values for the 2nd Point:");
         x = scan.nextDouble();
         y = scan.nextDouble();
         Point case6p2 = new Point(x, y);

         System.out.println("Enter x and y values for the 3rd Point:");
         x = scan.nextDouble();
         y = scan.nextDouble();
         Point case6p3 = new Point(x, y);
         System.out.println("Are they Collinear?: "+ case6p.isCollinear(case6p2, case6p3));
         break;
       default:
         System.out.println("This isn't one of the methods available.");
         System.out.println("Please enter a number between 1 and 6");      
      } 

} while((whichMethod >= 1) && (whichMethod <= 6));

Answer 1

You have your loop looping only if the user enters a VALID number instead of when they enter an invalid number. When doing this sort of thing, I tend to use sets so the Boolean logic is easy, even after 2 days of no sleep and 10 pots of cold coffee :)

Set<Integer> validInputs = new Set();
validInputs.add(1);
validInputs.add(2);


do {
// your stuff here

} while (!validInputs.contains(inputMethod));

If you ever move away from a console-based user interaction, having a set of valid values will help in both swing and JavaFX.

Answer 2

Add whichMethod = scan.nextInt() as the last line in the default. This will allow the user to enter the valid number if user had input incorrect number.