Draw? it could be said. (java) [closed]

It happens that we were given the task of creating a Main that can print the following figure with the use of "for":

 @
 @@@
@@@@@  en el caso n=3.
 @@@
  @



 @
  @@@
 @@@@@
@@@@@@@ en el caso de n=4.
 @@@@@
  @@@
   @

and so on successively ...   We were given the following method that meets the "half" ie:

@
  @@@
 @@@@@
@@@@@@@ en el caso de n=4.

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

Any ideas?