Java多线程框架源码阅读之---AQS的ConditionObject

前置文章为https://segmentfault.com/a/11...，若是不了解AQS的基本lock和unlock实现机制，建议先看一下这个文章。

Condition相似于wait和notify,notifyAll，经常使用于实现生产者消费者。如下代码是一个用ReentrantLock的condition作的一个生产者消费者例子。

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

class BoundedBuffer {
    final Lock lock = new ReentrantLock();
    // condition 依赖于 lock 来产生
    final Condition notFull = lock.newCondition();
    final Condition notEmpty = lock.newCondition();

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

    // 生产
    public void put(Object x) throws InterruptedException {
        lock.lock();
        try {
            while (count == items.length)
                notFull.await();  // 队列已满，等待，直到 not full 才能继续生产
            items[putptr] = x;
            if (++putptr == items.length) putptr = 0;
            ++count;
            notEmpty.signal(); // 生产成功，队列已经 not empty 了，发个通知出去
        } finally {
            lock.unlock();
        }
    }

    // 消费
    public Object take() throws InterruptedException {
        lock.lock();
        try {
            while (count == 0)
                notEmpty.await(); // 队列为空，等待，直到队列 not empty，才能继续消费
            Object x = items[takeptr];
            if (++takeptr == items.length) takeptr = 0;
            --count;
            notFull.signal(); // 被我消费掉一个，队列 not full 了，发个通知出去
            return x;
        } finally {
            lock.unlock();
        }
    }
}