How to fetch data's between two dates in android (not sqlite)?

I tried to do to fetch the data's between from and to dates. I did it on sql lite,it works and I tried in android coding part,it doesn't work,could you guys please help

protected void adddata1() throws ParseException {

Database db=new Database(Reportmonth.this);
SQLiteDatabase sb=db.getReadableDatabase();


String a=from.getText().toString();
String b=to.getText().toString();

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");


 Date a1=sdf.parse(a);//convert string to date
Date b1=sdf.parse(b);//convert string to date


Cursor cus=sb.rawQuery("select * from expenz where daty between '" + a1 +"' AND '"+b1+"'",null);

cus.moveToFirst();
 for(int i=0;i<cus.getCount();i++)
     {


     if(cus!=null) //i think the error starts from this onwards.


     {


         soi.setText(cus.getString(0));


         Log.i("",cus.getString(0));


          desc.setText(cus.getString(3));

          dat.setText(cus.getString(1));

          woc.setText(cus.getString(2));


          amount.setText(cus.getString(5));

          adddata();

          search.setClickable(false);

  }

     cus.moveToNext();

     } 

}