android - How to subtract two string values in java -

am having 2 string contaning integer values how can subtract string.

 string addquantity = quantity1.gettext().tostring();  string subquantity = quantity2.gettext().tostring();  int final_ = integer.parseint(addquantity) - integer.parseint(subquantity); 

i tried many methods showing error , me subtract value in string.

maybe edittexts not initialized, need quantity1 = (edittext) findviewbyid(r.id.your_edit_text_id) both.