code: public String encryptPassword(String plain) {
      Preconditions.checkArgument(this.encryptors.size() > 0,
          "A master password needs to be provided for encrypting passwords.");
  
      try {
        return this.encryptors.get(0).encrypt(plain);
      } catch (Exception e) {
        throw new RuntimeException("Failed to encrypt password", e);
      }
    }
docs: Encrypt a password. A master password must have been provided in the constructor.
  @param plain A plain password to be encrypted.
  @return The encrypted password.