private void addBillToList(String concept, int amount) { if (concept == "END") return; Bill bill = new Bill(concept, amount); if (firstBill == null) { firstBill = bill; return; } Bill current = firstBill; while (current != null) { if (current.getNextBill() == null) { current.setNextBill(bill); return; } current = current.getNextBill(); } return; }