public class TestExtend {
class A {
protected void print(String s){
System.out.println(s);
}
A() {print("A()");}
public void f() {print("A:f()");}
}
class B extends A {
B() {print("B()");}
public void f() {print("B:()");}
}
public static void main (String[] args) {
B b = new B(); --错误行,这行代码有问题
b.f();
}
}