class A
{
public void fun1()
{
System.out.println("<----A------>");
}
public void fun2()
System.out.println("<----B------>");
}
class B extends A
System.out.println("<----C------>"); //方法的覆写
public void fun3()
System.out.println("<----D------>");
class C extends A
System.out.println("<----E------>"); //方法的覆写
public void fun4()
System.out.println("<----F------>");
public class test39 {
public static void main(String args[])
fun(new A()); //传递A类型,向上转型
fun(new B()); //传递B类型,向上转型
fun(new C()); //传递C类型,向上转型
public static void fun(A a)
a.fun1();
![](https://img.laitimes.com/img/9ZDMuAjOiMmIsIjOiQnIsISPrdEZwZ1Rh5WNXp1bwNjW1ZUba9VZwlHdsATOfd3bkFGazxCMx8VesATMfhHLlN3XnxCMwEzX0xiRGZkRGZ0Xy9GbvNGLpZTY1EmMZVDUSFTU4VFRR9Fd4VGdsYTMfVmepNHLrJXYtJXZ0F2dvwVZnFWbp1zczV2YvJHctM3cv1Ce-YWan5iM4QTZhRjYxUzNyQmNyMGNxIGZhdDNxI2NkZmMxUmN08CXzAzLchDMxIDMy8CXn9Gbi9CXzV2Zh1WavwVbvNmLvR3YxUjL2M3Lc9CX6MHc0RHaiojIsJye.gif)