16. Scanner hasNextDouble example

• Code that gets a valid double value within a specified range

  
  Scanner sc = new Scanner(System.in);
  double subtotal = 0.0;
  boolean isValid = false;
  while (isValid == false)
  {
      // get a valid double value
      System.out.print("Enter subtotal:   ");
      if (sc.hasNextDouble())
      {
          subtotal = sc.nextDouble();
          isValid = true;
      }
      else
      {
          System.out.println(
              "Error! Invalid number. Try again.");
      }
      sc.nextLine();
      // discard any other data entered on the line
      // check the range of the double value
      if (isValid == true && subtotal <= 0)
      {
          System.out.println(
              "Error! Number must be greater than 0.");
          isValid = false;
      }
      else if (isValid == true && subtotal >= 10000)
      {
          System.out.println(
              "Error! Number must be less than 10000.");
          isValid = false;
      }
  }