@Override
  public String valueToString(final Object o) {
    if (o == null) {
      return null;
    }
    return o.toString();
  }
Filter for JFormattedTextField. Ensures valid filenames. Does not work for directories.

@param directory Directory where a file with the specified filename is temporarily created for
    validation purpose. http://stackoverflow.com/questions/893977/java-how-to-find-out-whether
    -a-file-name-is-valid
java/zylib/src/main/java/com/google/security/zynamics/zylib/gui/CFilenameFormatter.java