private boolean checkHasNoErrors(ExecutableElement element, Messager messager) {
        if (element.getModifiers().contains(Modifier.STATIC)) {
            messager.printMessage(Diagnostic.Kind.ERROR, "Subscriber method must not be static", element);
            return false;
        }

        if (!element.getModifiers().contains(Modifier.PUBLIC)) {
            messager.printMessage(Diagnostic.Kind.ERROR, "Subscriber method must be public", element);
            return false;
        }

        List<? extends VariableElement> parameters = ((ExecutableElement) element).getParameters();
        if (parameters.size() != 1) {
            messager.printMessage(Diagnostic.Kind.ERROR, "Subscriber method must have exactly 1 parameter", element);
            return false;
        }
        return true;
    }
Found subscriber methods for a class (without superclasses).
EventBusAnnotationProcessor/src/org/greenrobot/eventbus/annotationprocessor/EventBusAnnotationProcessor.java