java显示菱形点阵 java菱形星号

// 运行结果:

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

========================================================
//步骤

public class demo {
        public static void main(String[] args) {
            //定义行数
            int n = 4;
            shape(n);
        }
        //打印星星
        private static void shape(int n) {
            //打印上半部分
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < 2 * n; j++) {
                    if (j < n - i)
                        System.out.print(" ");
                    if (j >= n - i && j <= n + i)
                        System.out.print("*");
                }
                System.out.println();
            }
            //打印下半部分
            for (int i = 1; i < n; i++) {
                System.out.print(" ");
                for (int j = 0; j < 2 * n - i; j++) {
                    if (j < i)
                        System.out.print(" ");
                    if (j >= i && j < 2 * n - i - 1)
                        System.out.print("*");
                }
                System.out.println();
            }
        }
    }