How to call a Derived call fucntion with a base class object ?

Question

Hi all
i am working on a JNI interface to Java, and in the process of simulating a C++ behaviour in java
so i need some help form you people, in this regard.
here is a c++ code, i need a equivalent fucntionality in java , to put it one word, the question is
how to implement the dynamic_cast functionality in java, as java also has virtual fucntions, i think
this should be possible, if it is not, what is the alternative
class Base
public:
     Base()
     ~Base()
     virtual void F1()
          cout<<"The BASE::F1() is called"<<endl;
     virtual void F2()
          cout<<"The BASE::F2() is called"<<endl;
class Derived : public Base
public:
     Derived()
     ~Derived()
     virtual  void F3()
          cout<<"The Derived::F3() is called"<<endl;
     virtual void F4()
          cout<<"The Derived::F4() is called"<<endl;
Base * GetDerived()
     return new Derived();
int _tmain(int argc, _TCHAR* argv[])
     Base *ptr = NULL;
                ptr  = GetDerived();
     Derived *dPtr = dynamic_cast<Derived *>(ptr);
                dPtr->F3();
}regards
pradish

Answer 1

Just to clarify a point that I consider important--the distinction between references and objects:
Your subject is: How to call a Derived call fucntion with a base class object ? The answer to that is: You cannot. It is completely impossible in Java. If you have a base class object, the derivced class' methods are not present. On the other hand, if you have a compile-time reference of the parent type, but at runtime it happens to point to an instance of the derived class, then, as pointed out, you can cast the reference. (Note that casting does not apply to objects.)