code: private static void repairNullArgsAndWarnIfNecessary(String[] args) {
      boolean haveANullArg = false;
      for (String s : args) {
        if (s == null) {
          haveANullArg = true;
          break;
        }
      }
  
      if (haveANullArg) {
        Log.warn("Found a null command-line argument; printing all command-line arguments out now");
        printArgs(args);
      }
  
      for (int i = 0; i < args.length; i++) {
        String s = args[i];
        args[i] = (s == null) ? "" : s;
      }
    }
docs: This shouldn't be necessary, but is.  In one really weird Hadoop environment, we saw an argument coming across
  from the driver as null.  This shouldn't be possible but it happened.  So repair it here, by forcing a null
  to really be the empty string.
  
  @param args Array of command line arguments