private Coordinate inputPosition() {
        int x = 0;
        int y = 0;
        String[] str;
        String input;
        while (true) {
            System.out.println("Please input a Coordinate for droping Bomb !");
            System.out.println("Enter position （wie 9,8) : ");
            scPosition = new Scanner(System.in);
            input = scPosition.next().toUpperCase();
            if (input.equals("Q")) {
                x = -1;
                y = -1;
                break;
            } else {
                str = input.split(",");
                try {
                    x = Integer.parseInt(str[0]);
                    y = Integer.parseInt(str[1]);
                    if (x >= 0 && x < sea.getWidth() && y >= 0 && y < sea.getHeight()) {
                        break;
                    } else {
                        System.out.println("Input value of x or y is illegal");
                        System.out.println("Please try again !");
                        System.out.println();
                    }   
                    
                } catch (NumberFormatException e) {
                    System.out.println("The format of position is illegal. ");
                    System.out.println("The right format should be \"3,8\"");
                    System.out.println();
                } catch (ArrayIndexOutOfBoundsException e) {
                    System.out.println("The format of position is illegal. ");
                    System.out.println("The right format should be \"3,8\"");
                    System.out.println();
                }
            }
        }
        return sea.new Coordinate(x, y);
    }