I am trying to fetch data from database and place it in a ListView in android

I want to create a quiz app which contains 1ques and 4options for that i created a database from which the ques and options are fetched to 5 textviews using ListView.I surfed many tutorials and using a page from stackoverflow created it using ArrayList and Cursor but i am getting a error.LOGCAT java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.Cursor android.database.sqlite.SQLiteDatabase.query(java.lang.String, java.lang.String[], java.lang.String, java.lang.String[], java.lang.String, java.lang.String, java.lang.String)' on a null object reference at com.example.shark.shopapp.merge.getData(merge.java:26) at com.example.shark.shopapp.MainActivity.onCreate(MainActivity.java:68) It is showing in a Cursor.query() line.

MainActivity setContentView(R.layout.ques_layout); db=openOrCreateDatabase("check1.db",SQLiteDatabase.CREATE_IF_NECESSARY,null); db.execSQL("CREATE TABLE que(ques TEXT,optn1 TEXT,optn2 TEXT,optn3 TEXT,optn4 TEXT)"); ListView l1=(ListView)findViewById(R.id.listView2); merge mer=new merge(this); ArrayList<String> data=mer.getData(); l1.setAdapter(new ArrayAdapter<String>(this,R.layout.ques_layout,data)); db.close();

Merge.java public merge(Context c){ourContext=c;} public ArrayList<String> getData() { String[] columns = new String[]{ques, optn1, optn2, optn3, optn4}; Cursor c2=db.query(DATABASE_TABLE,columns,null,null,null,null,null); ArrayList<String> result = new ArrayList<String>(); int ques = c2.getColumnIndex("_id"); int optn1 = c2.getColumnIndex("optn1"); int optn2 = c2.getColumnIndex("optn2"); int optn3 = c2.getColumnIndex("optn3"); int optn4 = c2.getColumnIndex("optn4"); for (c2.moveToFirst(); !c2.isAfterLast(); c2.moveToNext()) { result.add(c2.getString(ques) + c2.getString(optn1) + c2.getString(optn2) + c2.getString(optn3) + c2.getString(optn4)); } db.close(); return result; } }