Room Using Date field

You're converting from Date to Long (wrapper) and from long (primitive) to Date. I changed it to Long and it compiled. Besides, unboxing null in your converter produces a NPE.

public class DateConverter {    @TypeConverter    public static Date toDate(Long dateLong){        return dateLong == null ? null: new Date(dateLong);    }    @TypeConverter    public static Long fromDate(Date date){        return date == null ? null : date.getTime();    }}

See my complete example.

Refer to the documentation : https://developer.android.com/training/data-storage/room/referencing-data

public class Converters {    @TypeConverter    public static Date fromTimestamp(Long value) {        return value == null ? null : new Date(value);    }    @TypeConverter    public static Long dateToTimestamp(Date date) {        return date == null ? null : date.getTime();    }}

Then map it to the database.

@Database(entities = {User.class}, version = 1)@TypeConverters({Converters.class})public abstract class AppDatabase extends RoomDatabase {    public abstract UserDao userDao();}

And the entity.

@Entitypublic class User {    private Date birthday;}

I had this same problem (how to store time to Room), but I was using Calendar, so I made this:[note: This anwer is for Calendar ; the main reason is that Calendar is now supported]

edit: the main reason for this answer is that Date is deprecated, so here you go

  @TypeConverter  public static Calendar toCalendar(Long l) {    Calendar c = Calendar.getInstance();    c.setTimeInMillis(l);    return c;  }  @TypeConverter  public static Long fromCalendar(Calendar c){    return c == null ? null : c.getTime().getTime();  }