get all (derived) interfaces of a class

Question

java.lang.Class.getInterfaces returns all directly implemented interfaces ie doesn't walk the class tree to get all interfaces of all parent types. eg For example the hierarchy

public interface A {}
public interface B {}
public interface C extends B {}

public class Foo implements A {} // Foo.class.getInterfaces() returns [A]
public class Bar implements C {} // Bar.class.getInterfaces() returns [C], note B is not included.

For Bar I would like to get [B, C], but for any arbitrary tree depth.

I could write this myself, but I'm sure a library must exist that does this already, any ideas?

I don't quite understand your question. Could you elaborate please? — fireshadow52, Jul 07 '11 at 19:34

score 52 · Accepted Answer · edited Nov 20 '15 at 11:56

52

Apache Commons Lang has method you need: ClassUtils.getAllInterfaces

edited Nov 20 '15 at 11:56

Steve Chambers

37,270
24
156
208

answered Jul 07 '11 at 19:37

Alex Gitelman

24,429
7
52
49

1

Much obliged, this is exactly what I was after. Thanks! – markdsievers Jul 07 '11 at 19:47

score 22 · Answer 2 · edited Jun 20 '20 at 09:12

22

Guava Solution:

final Set<TypeToken> tt = TypeToken.of(cls).getTypes().interfaces();

This is a much more powerful and cleaner reflection API than the ancient Apache stuff.

edited Jun 20 '20 at 09:12

Community

1
1

answered Jan 22 '16 at 16:55

+1 I was looking to get all interfaces so I could use the built in [newProxyInstance](https://docs.oracle.com/javase/8/docs/api/java/lang/reflect/Proxy.html#newProxyInstance-java.lang.ClassLoader-java.lang.Class:A-java.lang.reflect.InvocationHandler-) method and guava had a different method for creating dynamic proxies that was much more simple: 'Reflection.newProxy'. See [Reflection Explained](https://github.com/google/guava/wiki/ReflectionExplained) – akagixxer Sep 09 '16 at 17:00

score 8 · Answer 3 · answered Jul 18 '17 at 15:07

8

Don't forget, Spring Framework has many similar util classes like Apache Commons Lang. So there is: org.springframework.util.ClassUtils#getAllInterfaces

answered Jul 18 '17 at 15:07

Ihor Rybak

3,091
2
25
32

score 0 · Answer 4 · answered Feb 21 '23 at 12:48

public interface A {}

public interface B {}

public interface E extends B{ }

public class C implements A{}

public class D extends C implements E{}

public class App {

    public static void main(String[] args) {

        final List<Class<?>> result = getAllInterfaces(D.class);            
        for (Class<?> clazz : result) {
            System.out.println(clazz);
        }
    }

    public static List<Class<?>> getAllInterfaces(Class<?> clazz) {
        if (clazz == null) {
            System.out.println(">>>>>>>>>> Log : null argument ");
            return new ArrayList<>();
        }
        List<Class<?>> interfacesFound = new ArrayList<>();
        getAllInterfaces(clazz, interfacesFound);
        return interfacesFound;
    }

    private static void getAllInterfaces(Class<?> clazz,
                                         List<Class<?>> interfacesFound) {
        while (clazz != null) {
            Class<?>[] interfaces = clazz.getInterfaces();

            for (int i = 0; i < interfaces.length; i++) {
                if (!interfacesFound.contains(interfaces[i])) {
                    interfacesFound.add(interfaces[i]);
                    getAllInterfaces(interfaces[i], interfacesFound);
                }
            }
            clazz = clazz.getSuperclass();
        }
    }
}

score 0 · Answer 5 · answered Apr 05 '23 at 11:55

public List<Class<?>> getInterfaces(Class<?> type) {
    return Stream.of(type.getInterfaces())
                 .flatMap(interfaceType -> Stream.concat(Stream.of(interfaceType), getInterfaces(interfaceType).stream()))
                 .collect(Collectors.toList());
}

get all (derived) interfaces of a class

5 Answers5

Guava Solution:

Linked