Testing which interfaces a class/interface implements?

I want to test which interfaces a class/interface is implementing.

So I have a basic interface Adapter and some interfaces base on it (e.g. PermissionsAdapter). Now I get a variable typed as Adapter and now I want to get every interface based on Adapter that this variable is implementing.

A simple implementation:

import java.util.LinkedList;
import java.util.List;

public class Main {

    private interface A { }
    private interface BA extends A { }
    private interface CA extends A { }

    private interface X {}

    private class IB implements BA { }
    private class IC implements CA { }
    private class IBC implements BA, CA { }
    private class ICX implements CA, X { }
    private class IBCX implements BA, CA, X {}

    public Main() {
        this.test(new IB());
        this.test(new IC());
        this.test(new IBC());
        this.test(new ICX());
        this.test(new IBCX());
    }

    private void test(A a) {
        List<Class<? extends A>> result = this.getAdapterInterfaces(a);
        System.out.print(a.getClass().getSimpleName() + "{");
        for (Class<? extends A> class1 : result) {
            System.out.print(class1.getSimpleName() + ", ");
        }
        System.out.println("}");
    }

    @SuppressWarnings("unchecked")
    public List<Class<? extends A>> getAdapterInterfaces(A adapter) {
            List<Class<? extends A>> result = new LinkedList<Class<? extends A>>();
            Class<?>[] interfaces = adapter.getClass().getInterfaces();
            for (Class<?> clazz : interfaces) {
                    if (A.class.isInstance(clazz)) {
                        result.add((Class<? extends A>) clazz);
                    }
            }
            return result;
    }

    public static void main(String[] 开发者_C百科args) {
        new Main();
    }
}

Here is the Adapter the interface A and the PermissionsAdapter for example BA and CA is another adapter. X is only a sample interface, which the list shouldn't contain.

And the result:

IB{}
IC{}
IBC{}
ICX{}
IBCX{}

So it doesn't seem to work. Now where is my mistake in getAdapterInterfaces(A)? I think it is the test, but how could I test, if a class is a specific class of A?

Fabian

---

Your test A.class.isInstance(clazz) is wrong. It tests whether the interface's class object is of your A type, which it isn't (it is of type Class, Object, Serializable, AnnotatedElement, GenericDeclaration and Type (in 1.6), nothing more).

You want Class.isAssignableFrom, I think. (But read the documentation.)

Also, you might need to recurse to the superclass and the interfaces, since there could be indirect implementations.