Wie speichere ich dauerhaft Daten unter Android ?

public class DataBaseHelper extends SQLiteOpenHelper {


    //Datenbankname und Version
    public static final String DB_NAME = "budget.db";
    public static final int DB_VERSION = 1;

    //Tabellenname
    public static final String TABLE_BUDGET_LIST = "budget_list";

    //Spaltennamen in der Tabelle definieren
    public static final String COLUMN_ID = "_id";
    public static final String COLUMN_DATE="date";
    public static final String COLUMN_MONEY="money";
            ...

    //hier wird das CREATE TABLE Statement in einem String gespeichert um es später auszuführen
    public static final String SQL_CREATE = "CREATE TABLE " + TABLE_BUDGET_LIST +
            "(" +COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "+
            COLUMN_DATE+" INTEGER NOT NULL, "+ COLUMN_MONEY+" REAL NOT NULL"+ " );";

    public DataBaseHelper(Context context){
        super (context, DB_NAME, null, DB_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(SQL_CREATE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
}

CREATE TABLE tabellenname (
id  INTEGER PRIMARY KEY,
name TEXT,
adresse TEXT,
alter INTEGER
);

public class DataBaseSource {

    private static final String LOG_TAG = DataBaseSource.class.getSimpleName();

    private SQLiteDatabase database;
    private DataBaseHelper dbHelper;

    private String[] columns = {  
        DataBaseHelper.COLUMN_ID,
        DataBaseHelper.COLUMN_DATE,
        DataBaseHelper.COLUMN_MONEY
    };

    public DataBaseSource(Context context) {

        dbHelper = new DataBaseHelper(context);
    }

    public boolean open() {
        try{
            database = dbHelper.getWritableDatabase();
            return true;
        }
        catch (SQLiteException e){
            e.printStackTrace();
        }
        return false;
    }

    public void close() {
        dbHelper.close();

    }

    public BudgetItem insertBudgetItemToDB(String date, double money) {
        if(!database.isOpen())
            return null;

        ContentValues values = new ContentValues();
        values.put(DataBaseHelper.COLUMN_NUM, date);
        values.put(DataBaseHelper.COLUMN_MONEY, money);


        Cursor cursor = database.query(DataBaseHelper.TABLE_BUDGET_LIST,
                columns, DataBaseHelper.COLUMN_ID + "=" +
                database.insert(DataBaseHelper.TABLE_BUDGET_LIST, null, values),
                null, null, null, null);

        if(cursor==null||!cursor.moveToFirst())
            return null;

        BudgetItem bItem= cursorToBudgetItem (cursor);

        cursor.close();

        return bItem;
    }

    private BudgetItem cursorToBudgetItem(Cursor cursor) {
        BudgetItem tmpBI=null;
        try{
            tmpBI = new BudgetItem(
                cursor.getInt(cursor.getColumnIndexOrThrow(DataBaseHelper.COLUMN_ID)),
                cursor.getString(cursor.getColumnIndexOrThrow(DataBaseHelper.COLUMN_DATE)),
                cursor.getString(cursor.getColumnIndexOrThrow(DataBaseHelper.COLUMN_MONEY)));}
        catch(IllegalArgumentException e){
            e.printStacktrace();
        }
        return tmpBI;
    }

    public List<BudgetItem> getAllBudgetItemsFromDB() {
        List<BudgetItem> bItemList = new ArrayList<>();

        Cursor cursor = database.query(DataBaseHelper.TABLE_BUDGET_LIST,
                columns, null, null, null, null, null);

        if(cursor==null||!cursor.moveToFirst())
                return null;

        while(!cursor.isAfterLast()) {
            bItemList.add(cursorToBudgetItem(cursor));
            if(!cursor.moveToNext())
                return null;
        }

        cursor.close();

        return bItemList;
    }
}

public class BudgetItem{
    int id;
    String date;
    double money;
 
    private BudgetItem()

    public BudgetItem(int id,String date, double money){
        this.id=id;
        this.date=date;
        this.money=money;
    }

        DataBaseSource db=new DataBaseSource(context);
        if(!db.open())
            return;

        //Alles in der Datenbank wird in dieser Liste gespeichert
        List<BudgetItem> bItemList = db.getAllBudgetItemsFromDB())
        if(bItemList==null)
            return;

        //2 Einträge in die Datenbank einfügen
        BudgetItem bItmp=null;

        if((bItmp=db.insertBudgetItemToDB("09.02.2017", 53.85))!=null)
            bItemList.add(bItmp);
    
        if((bItmp=db.insertBudgetItemToDB("10.02.2017", 49.13))!=null)
            bItemList.add(bItmp);

        db.close();
        db=null;