code: private static void setConfigurationFromSystemProperties(Configuration configuration,
        PropertyKey[] propertyNames) {
      for (PropertyKey propertyName : propertyNames) {
        setConfigurationFromSystemProperty(configuration, propertyName.toString());
      }
    }
docs: Set the System properties into Hadoop configuration.
  
  This method won't override existing properties even if they are set as System properties.
  
  @param configuration Hadoop configuration
  @param propertyNames the properties to be set