identify the list of interface a object implements

Question

Is there a way to identify the list of interfaces a object implements. For example: LinkedList implements both List and Queue interfaces.

Is there any Java statement that I can use to determine it?

Answer 1

It sounds like you're looking for Class.getInterfaces():

public static void showInterfaces(Object obj) {
    for (Class<?> iface : obj.getClass().getInterfaces()) {
        System.out.println(iface.getName());
    }
}

For example, on an implementation of LinkedList that prints:

java.util.List
java.util.Deque
java.lang.Cloneable
java.io.Serializable

Note that java.util.Queue isn't displayed by this, because java.util.Deque extends it - so if you want all the interfaces implemented, you'd need to recurse. For example, with code like this:

public static void showInterfaces(Object obj) {
    showInterfaces(obj.getClass());
}

public static void showInterfaces(Class<?> clazz) {
    for (Class<?> iface : clazz.getInterfaces()) {
        System.out.println(iface.getName());
        showInterfaces(iface);
    }
}

... the output is:

java.util.List
java.util.Collection
java.lang.Iterable
java.util.Deque
java.util.Queue
java.util.Collection
java.lang.Iterable
java.lang.Cloneable
java.io.Serializable

... and now you'll note that Iterable and Collection occur twice :) You could collect the "interfaces seen so far" in a set, to avoid duplication.