code: public static TaskTrackerAction createAction(ActionType actionType) {
      TaskTrackerAction action = null;
      
      switch (actionType) {
      case LAUNCH_TASK:
        {
          action = new LaunchTaskAction();
        }
        break;
      case KILL_TASK:
        {
          action = new KillTaskAction();
        }
        break;
      case KILL_JOB:
        {
          action = new KillJobAction();
        }
        break;
      case REINIT_TRACKER:
        {
          action = new ReinitTrackerAction();
        }
        break;
      case COMMIT_TASK:
        {
          action = new CommitTaskAction();
        }
        break;
      }
  
      return action;
    }
docs: A factory-method to create objects of given {@link ActionType}.
  @param actionType the {@link ActionType} of object to create.
  @return an object of {@link ActionType}.