code: private boolean checkPackage(String className, String packageName) {
          if (packages.contains(packageName)) {
              cacheClassname(className);
              return true;
          }
          return false;
      }
docs: Checks if given class name is listed by package. If it's listed, then performance optimization is used and classname is
  added directly to {@code classes} collection.
  
  @param className   Class name to be checked.
  @param packageName Package name of the checked class.
  @return {@code true} iff class is listed by-package