嵌套循环

1.嵌套循环：将一个循环结构嵌套在另一个循环结构中。例如A在B中循环

2.外层循环：B

   内层循环:  A

3.假设外层循环了M次，内层循环了N次，一共循环了M*N次

4.外层控制行数，内层控制个数

package struct;

public class demo21 {
    public static void main(String[] args) {
        //输出五行星，每行四个
        for (int i = 1; i <= 5; i++) {
            for (int i1 = 1; i1 <=4; i1++) {

                System.out.print("*");
            }


            System.out.println();

        }
    }
}

package struct;

public class demo22 {
    public static void main(String[] args) {
        //输出一个菱形
        for (int i = 1; i <5; i++) {
            for (int j = 1; j <=6-i; j++) {
                System.out.print(" ");
            }
            for (int i1 = 1; i1 <i; i1++) {
                System.out.print("*");
            }
            for (int i1 = 1; i1 <=i; i1++) {
                System.out.print("*");
            }

            System.out.println();
        }
        for (int i = 1; i <=5; i++) {
            for (int i1 =1 ; i1 <=i; i1++) {
                System.out.print(" ");
            }
            for (int i1 = 1; i1 < 6-i; i1++) {
                System.out.print("*");
            }
            for (int i1 = 1; i1 <=6-i; i1++) {
                System.out.print("*");
            }
            System.out.println();
            }

        }


}