code: public static boolean isInnerClass(ClassNode cNode) {
          return cNode.redirect().getOuterClass() != null
                  && !Modifier.isStatic(cNode.getModifiers());
      }
docs: Detect whether a given ClassNode is a inner class (non-static).
  
  @param cNode the ClassNode of interest
  @return true if the given node is a (non-static) inner class, else false