Meta Generic in Java -

i'm 99% impossible, thought it's worth try: possible create class implements template?

motivation: want create generic composite class.

example:

public class genericcomposite<t> implements t {     list<t> m_items;      void add(t item) {         m_items.add(item);     }      @override     void f() {         (t item : m_items) {             item.f();         }     } } 

where f method defined in interface t. of course don't know it's gonna f() when call nor implement it. there meta-meta-magic i'm not aware of makes possible? if not, there other language out there supports this?

you correct, not possible in java: compiler cannot sure t interface (as opposed class), cannot let implement t.

c++ offers possibility through templates, not implement "generic composite". problem f() method (or methods in actual class stands). wanted write this:

// not going work! syntax not real. public class genericcomposite<t> implements t {     list<t> m_items;      void add(t item) {         m_items.add(item);     }      @override     <all-methods-of-t>(); } 

in order write @override void f() must know t has void f(). need know every single method of t, which, of course, defeats purpose of hiding t's identity in first place: genericcomposite<t> knows there know interface, i.e. methods.

when build composite, having list of sub-elements smaller problem implementing methods let callers treat composite in same way treat leaf objects. these "aggregate" methods custom, making generic structural implementations of composite useless.