code: private ProjectFile readFile(String inputFile) throws MPXJException
     {
        ProjectReader reader = new UniversalProjectReader();
        ProjectFile projectFile = reader.read(inputFile);
        if (projectFile == null)
        {
           throw new IllegalArgumentException("Unsupported file type");
        }
        return projectFile;
     }
docs: Use the universal project reader to open the file.
  Throw an exception if we can't determine the file type.
  
  @param inputFile file name
  @return ProjectFile instance