docs: private static Class checkClass(ProtoFile protoFile, TypeElement type, Map<String, String> mappedUniName,
              boolean isUniName) {
          String packageName = protoFile.packageName();
          String defaultClsName = type.name();
          // to check if has "java_package" option and "java_outer_classname"
          List<OptionElement> options = protoFile.options();
          if (options != null) {
              for (OptionElement option : options) {
                  if (option.name().equals(JAVA_PACKAGE_OPTION)) {
                      packageName = option.value().toString();
                  } else if (option.name().equals(JAVA_OUTER_CLASSNAME_OPTION)) {
                      defaultClsName = option.value().toString();
                  }
              }
          }
  
          String simpleName = getProxyClassName(defaultClsName, mappedUniName, isUniName);
          String className = packageName + PACKAGE_SPLIT_CHAR + simpleName;
  
          Class<?> c = null;
          try {
              c = Class.forName(className);
          } catch (ClassNotFoundException e1) {
              // if class not found so should generate a new java source class.
              c = null;
          }
  
          return c;
      }