Java并发包源码学习之AQS框架（三）LockSupport和interrupt

接着上一篇文章今天我们来介绍下LockSupport和Java中线程的中断（interrupt）。

其实除了LockSupport，Java之初就有Object对象的wait和notify方法可以实现线程的阻塞和唤醒。那么它们的区别 是什么呢？

主要的区别应该说是它们面向的对象不同。阻塞和唤醒是对于线程来说的，LockSupport的park/unpark更符合这个语义，以“线程”作为方法的参数， 语义更清晰，使用起来也更方便。而wait/notify的实现使得“线程”的阻塞/唤醒对线程本身来说是被动的，要准确的控制哪个线程、什么时候阻塞/唤醒很困难， 要不随机唤醒一个线程（notify）要不唤醒所有的（notifyAll）。

wait/notify最典型的例子应该就是生产者/消费者了：

class BoundedBuffer1 {
    private int contents;

    final Object[] items = new Object[100];
    int putptr, takeptr, count;

    public synchronized void put(Object x) {
        while (count == items.length) {
            try {
                wait();
            } catch (InterruptedException e) {
            }
        }

        items[putptr] = x;
        if (++putptr == items.length)
            putptr = 0;
        ++count;
        notifyAll();
    }

    public synchronized Object take() {
        while (count == 0) {
            try {
                wait();
            } catch (InterruptedException e) {
            }
        }
        Object x = items[takeptr];
        if (++takeptr == items.length)
            takeptr = 0;
        --count;
        notifyAll();
        return x;
    }

    public static class Producer implements Runnable {

        private BoundedBuffer1 q;

        Producer(BoundedBuffer1 q) {
            this.q = q;
            new Thread(this, "Producer").start();
        }

        int i = 0;

        public void run() {
            int i = 0;
            while (true) {
                q.put(i++);
            }
        }
    }

    public static class Consumer implements Runnable {

        private BoundedBuffer1 q;

        Consumer(BoundedBuffer1 q) {
            this.q = q;
            new Thread(this, "Consumer").start();
        }

        public void run() {
            while (true) {
                System.out.println(q.take());
            }
        }
    }

    public static void main(String[] args) throws InterruptedException {
        final BoundedBuffer1 buffer = new BoundedBuffer1();
        new Thread(new Producer(buffer)).start();
        new Thread(new Consumer(buffer)).start();
    }
}

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