for打印菱形

public class Demo30 
{
	public static void main(String[] args) 
	{
		//用*打印菱形
		//上三角
		for(int i = 1;i <= 4;i ++){//上三角的行数
			for(int j = 1;j<= 4-i;j++){//先打印空格
				//i:1,j:1,2,3
				System.out.print(" ");
			}
			for(int k = 1; k <= 2 * i - 1;k++){//打印*
				//i:1,k:1,i:2,K:1,2,3
				System.out.print("*");
			}
			System.out.println();
		}
		//下三角
		for(int i = 1;i < 4;i ++){
			for(int j = 1;j <= i;j++){
				System.out.print(" ");
			}
			for(int k = 1;k <= (4 * 2 -1)- 2 * i;k ++){
				//i:1,k:1,2,3,4,5
				System.out.print("*");
			}
			System.out.println();
		}
		System.out.println("Hello World!");
	}
}