密实的菱形

效果

    *
   ***
  *****
 *******
*********
 *******
  *****
   ***
    *

代码

    public static void main(String[] args) {
        int max = 6;
        for (int i = 0; i < max; i++){
            for (int j = max - 1; j > i; j--){
                System.out.print(" ");
            }
            for (int j = 0; j < 2 * i - 1; j++){
                System.out.print("*");
            }
            System.out.print("\n");
        }
        for (int i = max - 2; i > 0; i--){
            for (int j = i; j < max - 1; j++){
                System.out.print(" ");
            }
            for (int j = 2 * i - 1; j > 0; j--){
                System.out.print("*");
            }
            System.out.print("\n");
        }

    }

间隔的菱形

效果

    *
   * *
  * * *
 * * * *
* * * * *
 * * * *
  * * *
   * *
    *

代码

  public static void main(String[] args) {
        int max = 6;
        for (int i = 0; i < max; i++){
            for (int j = max - 1; j > i; j--){
                System.out.print(" ");
            }
            for (int j = 0; j < 2 * i - 1; j++){
                if ((j + 1) % 2 != 0){
                    System.out.print("*");
                }  else {
                    System.out.print(" ");
                }
            }
            System.out.print("\n");
        }
        for (int i = max - 2; i > 0; i--){
            for (int j = i; j < max - 1; j++){
                System.out.print(" ");
            }
            for (int j = 2 * i - 1; j > 0; j--){
                if (j % 2 != 0){
                    System.out.print("*");
                } else {
                    System.out.print(" ");
                }
            }
            System.out.print("\n");
        }

    }