java列印任意邊長的菱形

public static void printSomeStar() {
   Scanner sc = new Scanner(System.in);
    try {
        System.out.print("請輸入菱形邊長：");
        int a = sc.nextInt();
        for (int i = 1; i <= a; i++) {
            for (int j = 0; j < a - i; j++) {
                System.out.print(' ');
            }
            for (int j = 0; j < 2 * i - 1; j++) {
                System.out.print('*');
            }
            System.out.println();
        }

        for (int i = 1; i < a; i++) {
            for (int j = 0; j < i; j++) {
                System.out.print(' ');
            }
            for (int j = 0; j < 2 * (a - i) - 1; j++) {
                System.out.print('*');
            }
            System.out.println();
        }
    } catch (Exception e) {
        System.out.println("輸入不合法！請重新輸入");
        printSomeStar();
    }
}
           

執行結果：

請輸入菱形邊長：a
輸入不合法！請重新輸入
請輸入菱形邊長：4
   *
  ***
 *****
*******
 *****
  ***
   *