Java generic type

Question

When I have an interface

public interface Foo {
    T someMethod();
}

is there any way to assure that when some class implements t

Answer 1

This cannot be done because of Type Erasure.

EDIT :

I got down voted, here is more explanation :

public interface Foo;

T from above is available in run time, so it cannot be checked. However, one could custom annotation that could enforce this.