public void addQueenAt(XYLocation l){
  if (!(queenExistsAt(l)))   squares[l.getXCoOrdinate()][l.getYCoOrdinate()]=1;
}

public void addQueenAt ( XYLocation l ) { if ( ! ( queenExistsAt ( l ) ) ) squares [ l . getXCoOrdinate ( ) ] [ l . getYCoOrdinate ( ) ] = 1 ; }
column and row indices start with 0 !
