code: private static void getInterfaceMethods(Class<?> cls,
                                              Map<Signature, Method> sigs) {
          Class<?>[] intfs = cls.getInterfaces();
          for (int i=0; i < intfs.length; i++) {
              Class<?> intf = intfs[i];
              boolean done = getInternalPublicMethods(intf, sigs);
              if (!done) {
                  getInterfaceMethods(intf, sigs);
              }
          }
      }
docs: /*
  Process the immediate interfaces of this class or interface.