@Override
  public final int parseArguments(final Parameters params) throws CmdLineException {
    final String token = params.getParameter(0);
    try {
      File inFile = Paths.get(token).toFile();
      Validators.validateExists(inFile);
      setter.addValue(new FileInputStream(inFile));
    } catch (IOException e) {
      throw new CmdLineException(owner, e.getMessage(), e);
    }
    return 1;
  }
A {@code OptionHandle} that can handle input stream option.
tools/tinkey/src/main/java/com/google/crypto/tink/tinkey/InputStreamHandler.java