An equivalence for eval()

Question

adding objects to a Vector, I'd like to retreive them with the correct original class type :
Vector v = new Vector();
User visitor = new User(1,"joe");
History hist = new History(1);
v.addElement(visitor);
v.addElement(hist);
Object oVisitor = v.elementAt(0);
Object oHist = v.elementAt(1);
// of course here I know the class, but I want to guess before cast :
(oVisitor.getClass().getName())oVisitor.aMethodInUser();
// doesn't work.
may be I should eval() the last code line but I don't know if it's possible in Java ?
anyone a better idea?
thanks for your help.
Laurent.

Answer 1

// doesn't work.
may be I should eval() the last code line but I don't
know if it's possible in Java ?No it isn't.
anyone a better idea?If you really believe that you need to do this, then you are working with a bad design.
If you think more carefully about what you are trying to do, you will probably realise that you would achieve nothing by doing it, even if it was possible. The type of a reference is used only at compile-time, so attempting to change it at runtime is pointless.
What do you want to do with the objects after performing the cast? Call a particular method? If so, then you must know the type yourself at compile-time in order to know what method to call, in which case you can hard-code the cast. If the method is going to be the same in all classes, then simply having them all implement a common interface that declares that method will work, then you can cast to that interface.