用java编写小程序打印“金字塔”

package demo1;


public class Demo {

    public static void main(String[] args) 
    {
        int a=4;
        for(int i=1;i<=a;i++)
        {
            for(int k=1;k<=a-i;k++)
            {
                System.out.print(" ");
            }
            for(int j=1;j<=(i-1)*2+1;j++)
            {
                if(i==1||i==a)
                {
                System.out.print("*");
                }
                else
                {
                    if( j==1||j==(i-1)*2+1)
                    {
                        System.out.print("*");
                    }
                    else
                    {
                        System.out.print(" ");
                    }
                        
                }
            }
            System.out.println();
        }
        

    }

}