code: private static byte[] hash(String password, String salt) {
  
          Key key = Keys.generateSecretKey(password, salt);
          return key.getEncoded();
      }
docs: This method does the actual work of hashing a plaintext password string,
  using {@link Keys#generateSecretKey(String, String)}.
  
  @param password The plaintext password.
  @param salt     The salt value to use in the hash.
  @return The hash of the password.