问题
As a followup to this question, is it possible to write a single method that adds a Dog
to a suitable room? (In this example, it would accept either an Animal
room or a Dog
room.) Or am I forced to write two distinct methods as below? (I can't even rely on overloading because of type erasure).
public class Rooms {
interface Animal {}
class Dog implements Animal {}
class Room<T> {
void add(T t) {}
}
void addDogToAnimalRoom(Room<Animal> room) {
room.add(new Dog());
}
void addDogToDogRoom(Room<Dog> room) {
room.add(new Dog());
}
}
回答1:
You're using Room
as a consumer, since it's accepting the new Dog
, so Josh Bloch's famous PECS acronym applies.
void addDogToDogRoom(Room<? super Dog> room) {
room.add(new Dog());
}
来源:https://stackoverflow.com/questions/9929370/is-it-possible-to-write-a-single-method-that-accepts-a-generic-parameter-of-vary