class a_class;
   int id_;

   function new(int id);
      id_ = id;
   endfunction

   task display();
      $display("This is class %0d.", id_);
   endtask

endclass

// This should print the following:
//    This is class 2.
//    This is class 1.
module top;
   a_class ac1;
   a_class ac2;
   initial begin
      ac1 = new(1);
      ac2 = new(2);
      ac2.display();
      ac1.display();
   end
endmodule