code: public boolean addWorkingDir(String dirName) {
          if (dirName == null) {
              throw new NullPointerException();
          }
          return addToListInternal(currentWorkingDirectoryList, new File(dirName));
      }
docs: Add a working directory to the project.
  
  @param dirName
  the directory to add
  @return true if the working directory was added, or false if the working
  directory was already present