final.java

while (true) {
  BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
  try {
      System.out.print("Enter Mid exam score : ");
      double midScore = Double.parseDouble(br.readLine());
      System.out.print("Enter roll call score : ");
      double rollCall = Double.parseDouble(br.readLine());
      System.out.print("Enter final exam score : ");
      double finalScore = Double.parseDouble(br.readLine());
      double total = midScore * 0.3 + rollCall * 0.3 + finalScore * 0.4;
      System.out.println(total);

  } catch (NumberFormatException nfe) {
      System.err.println("Invalid Format!");
  } catch (IOException e) {
      e.printStackTrace();
  }
}