?????
古市轩 2011-03-16 08:21:51 class A
{
String a="class A";
}
class B extends A
{
String b="class B";
}
public class Exam3_17
{
public static void main(String [] args)
{
A a1=new A();
A a2=new A();
B b1=new B();
B b2=new B();
a1=b2;
b1=(B)a2;
System.out.println(a1.a);
System.out.println(b1.b);
}
}
//请问为什么编译能通过,却不能运行?