android - Need help editing values in Hashmap to be loaded in a listview -

i able value of "quantity" in list when use on click using code:

public void onitemclick(adapterview parent, view view, int position, long id)
{

         object o = list.get(position);             hashmap<?, ?> fullobject = (hashmap<?, ?>)o;             string = (string) fullobject.get("quantity");   

}

now want change value of "quantity" update in list. help? lot

now want change value of "quantity"

fullobject.put("quantity", whatever); 

then update in list

call notifydatasetchanged() on adapter, should reflect data change in ui.