Does java support class Foo<T super X> ,if no,why?

Question

Does java support class Foo<T super X> ,if no,why ?

Where T is a type parameter and X is a type.

Answer 1

No. The super keyword in the context of Generics could only be used in combination with a wildcard (?) when declaring (consumer) variables or method parameters (consumers) that are of some Generic type.

For example, these are valid:

List<? super Something> list = someListReference;

public void methodThatPopulatesAList(List<? super Something> consumer) {
    ...
    list.add(new Something());
    ...
}

More info:

• What is PECS?
• Wildcards in Java