java中怎样用for循环输出菱形,给出算法,谢谢!!

我写了一个 你看看吧
public class lingxing
{
public static void main(String[] args)
{
int i;
for(i=6;i>=0;i=i-2)
{
int j=1;
while(j++<=i)
{
System.out.print(" ");
}
for(j=1;j<=(13-2*i);j++)
System.out.print("*");
System.out.print("\n");

}
for(i=2;i<=6;i=i+2)
{
int j;
for(j=1;j<=i;j++)
System.out.print(" ");
for(j=1;j<=(13-2*i);j++)
System.out.print("*");
System.out.print("\n");
}
}

}