Create List of classes that extends and implement

Question

I have a several classes that define as follow :

class A extends Super implements Interface {}
class B extends Super implements Interface {}

I want to create list of these classes. I try the following:

public class C {

    List<Class<?>> classes = Arrays.asList((Class<?>) A.class, B.class); // Works
    List<Class<? extends Super,Interface>> classes2 = Arrays.asList(A.class, B.class); // Compile Error
    List<Class<? extends Super>> classes3 = Arrays.asList(A.class, B.class); // Compile Error

}

What is the right way to write it ? Why the first option works when I make casting only to A ?

What Java version are you using? 1 and 3 work fine for me. 2 doesn't work because `Class` only has one type parameter. — Sotirios Delimanolis, Aug 13 '14 at 14:41
Java1.7. 1 works for me too but I don't understand why if the casting is done only on A. For option 3 I got the error in eclipse:Type mismatch: cannot convert from List> to List> — user1291465, Aug 13 '14 at 14:44
If I remove the cast before A.class it I got from eclipse:Type mismatch: cannot convert from List> to List> — user1291465, Aug 13 '14 at 14:46
Ah, type inference changes. Removing the cast works on Java 8 only then. — Sotirios Delimanolis, Aug 13 '14 at 14:47
How can it be written without cast ? Why cast on A.class is enough and I don't need to cast B.class also ? — user1291465, Aug 13 '14 at 14:49

score 3 · Answer 1 · answered Aug 13 '14 at 14:52

line 1 :

it seems to be the way it works, but you can do this :

List<Class<?>> classes = new ArrayList<Class<?>>(Arrays.asList(A.class, B.class));

line 2 :

java: wrong number of type arguments; required 1

it should be List<Class<? extends Super>>

line 3 is ok on my IDE

line 4 (me) :

List<Class<? extends Super>> classes4 = new ArrayList<Class<? extends Super>>(Arrays.asList(A.class, B.class));

-

Arrays.asList() only return AbstractList and it fails when you use it (UnsupportedOperationException), so you must instanciate a implementation.

Thanks

Create List of classes that extends and implement

1 Answers1