code: public static boolean isConcrete( Class<?> clazz ) {
          return !Modifier.isAbstract(clazz.getModifiers()) &&
                  !Modifier.isInterface(clazz.getModifiers());
      }
docs: Is the specified class a concrete implementation of baseClass?
  @param clazz Class to check.
  @return True if clazz is concrete.  False otherwise.