code: public void clearReceipt( String receipt_id ) {
      synchronized( _receipts ) {
        for (Iterator i=_receipts.iterator(); i.hasNext();) {
          String o = (String)i.next();
          if (o.equals(receipt_id)) i.remove();
        }
      }
    }
docs: Deletes all receipts with a given ID
  
  @param receipt_id the id of the receipts to delete