}

  /*
   * Our implementation works fine with a null `dir`. However, there's nothing in the documentation
   * of the supertype that suggests that implementations are expected to tolerate null. That said, I
   * see calls in Google code that pass a null `dir` to a FilenameFilter.... So let's declare the
   * parameter as non-nullable (since passing null to a FilenameFilter is unsafe in general), but if