Java中不同类对象的线程

Question

I have 2 java class "LegacyDAO" and "NewDAO" implementing Runnable. In an another class "Test" we create one object of each LegacyDAOObj and NewDAOObj.

    Class Test {
        public static void main(String args[]) {
            LegacyDAO legacyDAOObj= new LegacyDAO();
            NewDAO newDAOObj= new NewDAO();

            Thread legacyDBThread= new Thread(legacyDAOObj);
            Thread newDBThread= new Thread(newDAOObj);
        }
    }

Is there any relation between legacyDBThread and newDBThread ? If I want newDBThread to execute some code and then wait for legacyDBThread to finish and then continue running. How can this be achieved ?

Answer 1

wait() and notify() API is helpful here. you can share some objects in two class and use wait-notify on these shared objects to sync two thread.

Answer 2

You can use countdown latch. Create a count down latch with count one, pass it to legacyDAOObj . After the logic executed in legacyDAOObj , count down the latch. Till the logic is executed in legacyDAOObj , newDAOObj awaits.

Answer 3

如果只想等待线程结束，请使用Thread＃join（） ，这似乎是实现所需目标的最简单方法。

Answer 4

CountdownLatch will be your best bet. Your newDaoObj will continue in main thread once legacyDaoObj finishes.

public static void main(String[] args) {
CountDownLatch start =new CountDownlatch(1);

    LegacyDAO legacyDAOObj= new LegacyDAO();
    NewDAO newDAOObj= new NewDAO();
    new Thread(new Worker(legacyDAOObj)).start();
    try {
        start.await();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    newDAOObj.doSomething();
}


public static class Worker implements Runnable{
    LegacyDAO dao;
    public Worker(LegacyDAO dao) {
        this.dao = dao;
    }
    @Override
    public void run() {
        try {
            start.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        dao.doSomething();
        start.countDown();
    }
}