Since Java lacks generics, there are many kinds of code which require duplicate code in Java. Specifically, every place where you would use generics in another language (Templates in C++, or TypeClasses in Haskell, for instance).
You can use "? extends SomeInterface" only if you write SomeInterface wrappers for every type which you want to use "generically." This is boilerplate relative to most other languages.
// T here is a type that must support these two operations:
// bool froznit();
// void frobnob(Foo* foo);
template <class T> class Frozner { ... }
public interface SomeStupidName {
public bool froznit();
public void frobnob(Foo foo);
}
public class Frozner<? extends SomeStupidName> { ... }