How to input and output A Object data in Android Jetpack Workmanger?

In Android Jetpack WorkManger, define a output data in Worker:

new Data.Builder().putLong(xxx);

there are putLong, putString, putBoolean, BUT there are not define a function to put a Object.

How can i output a Entity Object in Worker.

public class DownloadDB extends Worker {
    private static final String TAG = "DownloadDB";
    private List<ChoiceTestItem> mChoiceTestItems;

    public DownloadDB(@NonNull Context context, @NonNull WorkerParameters workerParams) {
        super(context, workerParams);
    }

    @NonNull
    @Override
    public Result doWork() {
        downChoiceTestItemFromNetwork();
        HashMap<String, Object> map = new HashMap<>();

        //Wrong Code here!!!
        map.put("a", mChoiceTestItems);
        @SuppressLint("RestrictedApi") Data data = new Data.Builder().putAll(map).build();

        return Result.success(data);
    }
...

there are not define a function to put a Object.

Correct. You cannot put arbitrary objects into a Data. As the documentation states: "This is a lightweight container, and should not be considered your data store". Not allowing arbitrary data types is one way they are enforcing this.

How can i output a Entity Object in Worker.

If by "Entity Object" you mean a Room @Entity, put the entity in your database. Put the primary key or other identifier into the Data, and use that to retrieve the entity at a later point from the database.