Help me with java

I am a freshman computer science student and one of my new subject is java programming. We were ask to make a diamond program using for loop and the diamond should be made of (*). I write a diamond program, though its correct, my instructor told me to simplify this using other method. Please Help Me! many tnx to you!
This is my program:
//Diamond program
public class Diamond{
public static void main(String[] args){

for (int a=1; a<6; a++){
System.out.print(" ");

for (int a=1; a<6; a++){
System.out.print(" ");
for (int c=a; c>=1; c--)
System.out.print("*");
for (int c=2; c<=a; c++)
System.out.print("*");
System.out.println();
}
for (int d=4; d>=1; d--){
for(int e=6; e>=1+d; e--)
System.out.print(" ");
for( int f=d; f>=1; f--)
System.out.print("*");
for(int f=2; f<=d; f++)
System.out.print("*");
System.out.println();
}
}
}//end