4.用for循环打印九九乘法表和等边三角形

1.用for循环打印九九乘法表

for (int i = 1; i <= 9; i++) {
            for (int j = 1; j <= i; j++) {
                System.out.print(i+"*"+j+"="+(i*j));
                System.out.print("   ");
            }
            System.out.println();

 

2.用for循环打印等边三角形

        for (int i = 1; i <= 10; i++) {//最外层循环，循环次数就是层数
            for (int j = 10; j >= i; j--) {//左上角空白区域的循环
                System.out.print(" ");
            }
            for (int k = 1;k<=i;k++){//三角形的左半边循环
                System.out.print(1);
            }
            for (int k = 1;k<i;k++){//三角形的右半边循环
                System.out.print(1);
            }
            System.out.println();//一层循环完要换行
        }