Hibernate了解方法的用途

Question

我正在尝试解决tutorial，最后我注意到在运行主类时：

public class App {
    public static void main(String[] args) {

        System.out.println("Hibernate one to many (Annotation)");
    Session session = HibernateUtil.getSessionFactory().openSession();

    session.beginTransaction();

    Stock stock = new Stock();
        stock.setStockCode("7052");
        stock.setStockName("PADINI");
        session.save(stock);

        StockDailyRecord stockDailyRecords = new StockDailyRecord();
        stockDailyRecords.setPriceOpen(new Float("1.2"));
        stockDailyRecords.setPriceClose(new Float("1.1"));
        stockDailyRecords.setPriceChange(new Float("10.0"));
        stockDailyRecords.setVolume(3000000L);
        stockDailyRecords.setDate(new Date());

        stockDailyRecords.setStock(stock);        
        stock.getStockDailyRecords().add(stockDailyRecords);

        session.save(stockDailyRecords);

    session.getTransaction().commit();
    System.out.println("Done");
    }

在这一行，

    stock.getStockDailyRecords().add(stockDailyRecords);

我无法理解它有用的是什么？我试图删除它，但它插入行没有任何问题，那么它的用途是什么？为什么他没有使用setDailyRecords(stockDailyRecords)代替，是否有一些我不理解的东西？