The program does not have an input check at the early phase. A wrong input will lead to program crash. To avoid this, a input check statement is added. The implementation is as follows:


Former partial code:

 System.out.println("Please input start move");
            int start_x = 0;
            int start_y = 0;

            if (in.hasNextInt()) {
                start_x = in.nextInt();
                start_y = in.nextInt();
            }

            Point ps = new Point(start_x, start_y);
            StartMove start_m = new StartMove(ps);



New partial code:

System.out.println("Please input start move");
            int start_x = 0;
            int start_y = 0;

            // if start_x or start_y is out of range [0,8]
            do {
                if (in.hasNextInt()) {
                    start_x = in.nextInt();
                    start_y = in.nextInt();
                }
            } while (start_x < 0 || start_x > 8 || start_y < 0 || start_y > 8);
            Point ps = Graph.getInstance().chessboard[start_x][start_y];