code: private void checkWorkingDir(File dir) {
          if (dir != null) {
              if (!dir.exists()) {
                  throw new CommandLineException("Working directory \"" + dir.getAbsolutePath() + "\" does not exist!");
              } else if (!dir.isDirectory()) {
                  throw new CommandLineException("Path \"" + dir.getAbsolutePath() + "\" does not specify a "
                          + "directory.");
              }
          }
      }
docs: and not a valid working directory