code: public static String buildKey(Class<?> clazz, String name) {
          return new StringBuilder().append(clazz.getCanonicalName()).append(".").append(name).toString();
      }
docs: Build a custom bundle key name, to avoid conflict the bundle key name among the activities.
  This is also useful to build a intent extra key name.
  
  @param clazz the class.
  @param name the key name, in most case the name is UPPER_UNDERSCORE.
  @return the full qualified key name.