private static void isSet(String... strings) {
    for (String str : strings) {
      Preconditions.checkState(!Strings.isNullOrEmpty(str));
    }
  }
Checks all {@code strings} are have non-null and non-empty values.
portability-spi-cloud/src/main/java/org/datatransferproject/spi/cloud/types/PortabilityJob.java