Minimize activity on back key press

OnBack Key press i want to minimize the application, How can i do this???

public boolean onKeyDown(int keyCode, KeyEvent event) {

   if (keyCode == KeyEvent.KEYCODE_BACK) {

           //Here i want to put minimize code.. pls give me this statement

       return true;
   }
   return super.onKeyDown(keyCode, event);

}

Thanks