code: public static PermissionStatus createImmutable(
        String user, String group, FsPermission permission) {
      return new PermissionStatus(user, group, permission) {
        public PermissionStatus applyUMask(FsPermission umask) {
          throw new UnsupportedOperationException();
        }
        public void readFields(DataInput in) throws IOException {
          throw new UnsupportedOperationException();
        }
      };
    }
docs: Create an immutable {@link PermissionStatus} object.