code: private static android.app.job.IJobCallback getCallback(android.app.job.JobParameters params) {
          Method method;
          try {
              method = params.getClass().getDeclaredMethod("getCallback");
              method.setAccessible(true);
              return (android.app.job.IJobCallback) method.invoke(params);
          } catch (NoSuchMethodException e) {
              throw new RuntimeException(e);
          } catch (InvocationTargetException e) {
              throw new RuntimeException(e);
          } catch (IllegalAccessException e) {
              throw new RuntimeException(e);
          }
      }
docs: getCallback() is a hidden method on JobParameters, so use reflection to get at it.