Initializing Multiple Variables in a FOR Loop

i in fact has not been initialized. for(int i=0, j=0;.... ); will do the trick for you.

It's because you didn't initialized variable i, maybe zero or else.

for(int i = 0, j = 0; i < this.board.length; i++, j++)
            if(j > 10)
                System.out.println();
            else
                System.out.print(this.board[i]);

Don't forget to initialize a variable If some objects are using it.