Nested extends in generics

Question

I have three classes:

class ClassR {}
class ClassA<T extends ClassR>{}    
class ClassB<E extends ClassA<T extends ClassR>> extends ClassA<T> {
    void foo(T param) {
    }

    void bar(E param) {
    }
}

The third class does not compile unless I change it to

class ClassB<E extends ClassA<T>, T extends ClassR> extends ClassA<T> {
    void foo(T bar) {
    }

    void bar(E param) {
    }
}

Is there a way to keep only E parameter I need to pass when creating ClassB, and T being inferred? For example, it would be convenient to use:

new ClassB<ClassA<ClassR>>()

instead of:

new ClassB<ClassA<ClassR>, ClassR>()

Answer 1

This even simpler approach might work for you:

class ClassR {}
class ClassA<T extends ClassR>{}    

class ClassB<T extends ClassR> extends ClassA<T> {
    void foo(T bar) {
    }

    void bar(ClassA<T> param) {
    }
}

And usage then bypasses any reference to ClassA to become:

class SubR extends ClassR {}

ClassB<SubR> obj = new ClassB<SubR>();