打印菱形

1.实心菱形

public class Demo9 {
    public static void main(String[] args) {
        for (int i = 1; i <= 5; i++) {
            //空格
            for (int j = 1; j <= 5 - i; j++) {
                System.out.print(" ");
            }
            for (int j = 1; j <= 2 * i - 1; j++) {
                System.out.print("*");
            }
            System.out.println();
        }
        for (int i = 1; i <= 4; i++) {
            for (int j = 1; j <= i; j++) {
                System.out.print(" ");
            }
            for (int j = 1; j <= 2*(5-i)-1; j++) {
                System.out.print("*");
            }
            System.out.println();
        }
    }
}

2.空心菱形

public class Demo10 {
    public static void main(String[] args) {
        //行数
        for (int i=1;i<=5;i++) {
            //空格
            for(int j=1;j<=5-i;j++) {
                System.out.print(" ");
            }
            //列数
            for(int j=1;j<=2*i-1;j++) {
                if(j==1 || j==2*i-1){
                    System.out.print("*");
                }else{
                    System.out.print(" ");
                }
            }
            System.out.println();
        }
        //倒三角形的行数
        for (int i=1;i<=4;i++) {
            for (int j=1;j<=i;j++) {
                System.out.print(" ");
            }
            //列数
            for (int j=1;j<=2*(5-i)-1;j++) {
                if(j==1 || j==2*(5-i)-1) {
                    System.out.print("*");
                }else{
                    System.out.print(" ");
                }
            }
            System.out.println();
        }
    }
}