Question

I have a variable that has several upper bounded wildcards, like so:

private Map< Class< ? extends MyClass1 >, List< ? extends MyClass2< ? extends MyClass3, ? extends  MyClass1> > > _variableName;

Is there any way to enforce that the bound value ? extends MyClass1 be the same for the Type of the Class class and the 2nd param of the MyClass2 class?

Answer 1

Yes:

    public class Foo<T extends MyClass1> {
        private Map< Class<T>, List<? extends MyClass2<? extends MyClass3, T>>> bar;
        ...
    }

You could also do this with a generic method. It depends on where you want to make the guarantee (and by extension, where the Map is instantiated), when defining the class or when calling a method that instantiates this Map.

UPDATE:

In response to the (correct) observation that this map will only contain one element, perhaps the questioner had this in mind instead:

    public class Foo {
        private Map<Class<? extends MyClass1>, List<? extends MyClass2<? extends MyClass3, ? extends MyClass1>>> bar;

        public <T extends MyClass1> void add(Class<T> myClass, List<? extends MyClass2<? extends MyClass3, T>>> myList) {
            bar.put(myClass, myList);
        }

        ...
    }

Assuming this is the only way to add elements to your private map, then that ensures the types always match.