Question

E.g. I have:

interface Consumer<F extends FoodType>
interface Vegetarian extends Consumer<Grass>
interface Predator extends Consumer<Meat>

I want to have something like:

class Feeder<C extends Consumer<F>>

to use F type parameter within Feeder class declaration. The aim is to pass only informative type parameter and to take up other type parameters from the passed ones:

new Feeder<Vegetarian>().buyFood(bluegrassIsGrassAndCouldNotBeMeat)

Answer 1

If the class is going to use two generic types it’s going to need two generic parameters even if they are dependent.

class Feeder<C extends Consumer<F>, F extends FoodType>{}

If may be useful to be a bit more flexible.

class Feeder<C extends Consumer<? super F>, F extends FoodType>{}

(Josh Bloch’s uses the acronym PECS: Producer’s extend; Consumer’s super.)