学步园

public class PolyTest4
{
                          public void run (Car car)
                       {
                             car.run();
                        }
                 public static void main(String[] args)
      {
                 PolyTest4 test = new PolyTest4();
                 Car car = new BMW();
                 test.run(car);

                 QQ qq = new QQ();
                test.run(qq);
 
      }
}
                  class Car
          {
                 public void run()
                  {
                    System.out.println("car is running");
                   }
            }
                 class BMW extends Car
{
                  public void run()
      {
              System.out.println("BMW is running");
      }
}
              class QQ extends Car
{
          public void run()
           {
             System.out.println("QQ is running");
           }
}