Tutorial AndroidOS SQLite

package com.tutorial.contatore;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;

public class dbManage {
    private SQLiteHelper sqLiteHelper;
    private SQLiteDatabase sqLiteDatabase;
    private Context context;

    private static final String MYDATABASE_NAME = "db";
    private static final int MYDATABASE_VERSION = 2;
    private static final String MYDATABASE_TABLE = "main";

    private static final String SCRIPT_CREATE_DATABASE =
            "create table " + MYDATABASE_TABLE + " ("
            + "nome text primary key, "
            + "valore integer not null"
            + ");";

    public dbManage(Context context) {
        this.context=context;
    }

    public dbManage openToRead() throws android.database.SQLException {
        sqLiteHelper = new SQLiteHelper(context, MYDATABASE_NAME, null, MYDATABASE_VERSION);
        sqLiteDatabase = sqLiteHelper.getReadableDatabase();
        return this;
    }

    public dbManage openToWrite() throws android.database.SQLException {
        sqLiteHelper = new SQLiteHelper(context, MYDATABASE_NAME, null, MYDATABASE_VERSION);
        sqLiteDatabase = sqLiteHelper.getWritableDatabase();
        return this;
    }

    public void close(){
        sqLiteHelper.close();
    }

    public long insert(String n, int v){
        ContentValues contentValues = new ContentValues();
        contentValues.put("nome", n);
        contentValues.put("valore", v);
        return sqLiteDatabase.insert(MYDATABASE_TABLE, null, contentValues);
    }

    public int deleteAll(){
        return sqLiteDatabase.delete(MYDATABASE_TABLE, null, null);
    }

    public Cursor queueAll(){
        String[] columns = new String[]{"nome","valore"};
        Cursor cursor = sqLiteDatabase.query(MYDATABASE_TABLE, columns, null, null, null, null, null);
        return cursor;
    }

    class SQLiteHelper extends SQLiteOpenHelper {

        public SQLiteHelper(Context context, String name,CursorFactory factory, int version) {
            super(context, name, factory, version);
        }

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

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            db.execSQL("DROP TABLE IF EXISTS main");
            onCreate(db);
        }
    }
}