Pattern-11

*      *

**    **

***  ***

********

********

**** ***

***  ***

**    **

*      *

Solution: 

public class Butterfly {

   public static void main(String args[]) {

       int n = 4; 

       //upper part

       for(int i=1; i<=n; i++) {

           for(int j=1; j<=i; j++) {

               System.out.print("*");

           } 

           int spaces = 2 * (n-i);

           for(int j=1; j<=spaces; j++) {

               System.out.print(" ");

           } 

           for(int j=1; j<=i; j++) {

               System.out.print("*");

           }

           System.out.println();

       }