AppDatabase

AppDatabase.java

@Database(entities = {CategoryData.class}, version = DATABASE_VERSION)
public abstract class AppDatabase extends RoomDatabase {

    private static AppDatabase INSTANCE;

    /*Database Constant*/
    @SuppressWarnings("WeakerAccess")
    public final static int DATABASE_VERSION = 1;
    public final static String DATABASE_NAME = "App.db";

    /*Category Contract*/
    public static final String CATEGORY_TABLE_NAME = "category";
    public static final String COLUMN_NAME_ID = "id";
    public static final String COLUMN_NAME_DESCRIPTION = "description";
    public static final String COLUMN_NAME_NAME = "name";
    public static final String COLUMN_NAME_COUNT = "count";


    public abstract CategoryDao getCategoryDao();

    public static AppDatabase getAppDatabase(Context context) {
        if (INSTANCE == null) {
            INSTANCE =
                    Room.databaseBuilder(context.getApplicationContext(), AppDatabase.class, DATABASE_NAME)
                            // allow queries on the main thread.
                            // Don't do this on a real app! See PersistenceBasicSample for an example.
                            .allowMainThreadQueries()
                            .build();
        }
        return INSTANCE;
    }

    public static void destroyInstance() {
        INSTANCE = null;
    }
}