java - 使用线程锁定系统的偶数奇数

Question

今天我在线程上做了一些练习，并尝试创建一个偶数奇数程序。我使用同步创建了这个，并且运行良好。但是当我尝试使用 Lock 做同样的事情时，我卡住了。

下面是我尝试执行相同操作的代码。

public class OddEvenNumberThreadLock {

public static void main(String args[]) {

    SharedObject sharedObject = new SharedObject();

    Thread evenThread = new Thread(new EvenNumber(sharedObject));
    Thread oddThread = new Thread(new OddNumber(sharedObject));

    evenThread.start();
    oddThread.start();
}

}



 class EvenNumber implements Runnable {
SharedObject object;

public EvenNumber(SharedObject object) {
    this.object = object;
}

@Override
public void run() {

    for (int i = 0; i <= 100; i = i + 2) {

        while (!object.isOdd()) {
            object.getLock().lock();
            try {
                System.out.println("Even : " + i);
                object.setOdd(true);
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                object.getLock().unlock();

            }

        }

    }

}

}
class OddNumber implements Runnable {
SharedObject object;

public OddNumber(SharedObject object) {
    this.object = object;
}

@Override
public void run() {

    for (int i = 1; i <= 100; i = i + 2) {

        while (object.isOdd()) {
            object.getLock().lock();
            try {
                System.out.println("Odd : " + i);
                object.setOdd(false);
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                object.getLock().unlock();

            }

        }

    }

}
}

class SharedObject {
private Lock lock;
private boolean isOdd;

public SharedObject() {
    this.lock = new ReentrantLock();

}

public boolean isOdd() {
    return isOdd;
}

public void setOdd(boolean isOdd) {
    this.isOdd = isOdd;
}

public Lock getLock() {
    return lock;
}

public void setLock(Lock lock) {
    this.lock = lock;
}
}

我还有一个问题，就像在同步的情况下，我们使用通知方法来通知其他线程。在Lock的情况下我们如何实现这个目标。

谢谢

Answer 1

据我所知，您希望实现您的两个线程以乒乓方式打印偶数和奇数。使用 ReentrantLock 比使用 synchronized block 更容易实现您想要的行为，因为 synchronized 总是不公平的，但您可以使 ReentrantLock 公平地说，使用适当的构造函数。以下是使用 Lock 后程序的样子:

public class App {

    public static void main(String args[]) {

        SharedObject sharedObject = new SharedObject();

        Thread evenThread = new Thread(new EvenNumber(sharedObject));
        Thread oddThread = new Thread(new OddNumber(sharedObject));

        evenThread.start();
        oddThread.start();
    }

}


class EvenNumber implements Runnable {
    SharedObject object;

    public EvenNumber(SharedObject object) {
        this.object = object;
    }

    public void run() {
        int i = 0;
        while(i <= 100) {
            object.getLock().lock();
            try {
                if (!object.isOdd()) {
                    System.out.println("Even : " + i);
                    i = i + 2;
                    object.setOdd(true);
                }
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                object.getLock().unlock();

            }
        }
    }
}

class OddNumber implements Runnable {
    SharedObject object;

    public OddNumber(SharedObject object) {
        this.object = object;
    }

    public void run() {
        int i = 1;
        while(i <= 100) {

            object.getLock().lock();
            try {
                if(object.isOdd()) {
                    System.out.println("Odd : " + i);
                    i = i + 2;
                    object.setOdd(false);
                }
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                object.getLock().unlock();

            }

        }

    }
}

class SharedObject {
    private Lock lock;
    private boolean isOdd;

    public SharedObject() {
        this.lock = new ReentrantLock(true);

    }

    public boolean isOdd() {
        return isOdd;
    }

    public void setOdd(boolean isOdd) {
        this.isOdd = isOdd;
    }

    public Lock getLock() {
        return lock;
    }

    public void setLock(Lock lock) {
        this.lock = lock;
    }

}