How to pass empty list with type parameter?

Question

class User{
    private int id;
    private String name;

    public User(int id, String name) {
        this.id = id;
        this.name = name;
    }
}

class Service<T> {
    private List<T> data;
    public void setData(List<T> data) {
        this.data = data;
    }
}

public class ServiceTest {
    public static void main(String[] args) {
        Service<User> result=new Service<User>();
        result.setData(Collections.emptyList()); // problem is here
    }
}

How to pass empty list with type parameter?

compiler giving me error message:

The method setData(List< User > ) in the type Service is not applicable for the arguments (List< Object > )

and if I try to cast with List then the error:

Cannot cast from List< Object > to List< User >

result.setData(new ArrayList<User>()); is working fine but I don't want to pass it.

Solution 1

Collections.emptyList() is generic, but you're using it in its raw version.

You can explicitly set the type-parameter with:

result.setData(Collections.<User>emptyList());

Solution 2

simply result.setData(Collections.<User>emptyList());