Java精通并发-通过Condition实现线程间通信实例剖析【下】

在上一次完成了Condition线程同步的实例，但是还木有对其运行流程进行分析，所以这次对它进行一个细致的分析，并且再对其代码做一些调整加深对其的印象，先回顾一下上次的代码：

public class MyTest2 {
    public static void main(String[] args) {
        BoundedContainer boundedContainer = new BoundedContainer();

        //利用java8的流来产生多个生产者线程
        IntStream.range(0, 10).forEach(i -> new Thread(() -> {
            try {
                boundedContainer.put("hello");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }).start());
        //利用java8的流来产生多个生产者线程
        IntStream.range(0, 10).forEach(i -> new Thread(() -> {
            try {
                boundedContainer.take();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }).start());
    }
}

class BoundedContainer {
    private String[] elements = new String[10];
    private Lock lock = new ReentrantLock();
    private Condition notEmptyCondition = lock.newCondition();
    private Condition notFullCondition = lock.newCondition();
    private int elementCount;//elements数组中已有的元素数量
    private int putIndex;
    private int takeIndex;

    public void put(String element) throws InterruptedException {
        this.lock.lock();
        try {
            while (this.elementCount == this.elements.length) {
                notFullCondition.await();
            }

            elements[putIndex] = element;
            if (++putIndex == this.elements.length) {
                putIndex = 0;
            }
            ++elementCount;
            System.out.println("put method: " + Arrays.toString(elements));

            notEmptyCondition.signal();

        } finally {
            this.lock.unlock();
        }
    }

    public String take() throws InterruptedException {
        this.lock.lock();

        try {
            while (0 == this.elementCount) {
                notEmptyCondition.await();
            }
            String element = elements[takeIndex];
            elements[takeIndex] = null;

            if (++takeIndex == elements.length) {
                takeIndex = 0;
            }

            --elementCount;
            System.out.println("take method: " + Arrays.toString(elements));

            notFullCondition.signal();

            return element;

        } finally {
            this.lock.unlock();
        }
    }
}

其运行结果如下：

所以在结果的输出上也存在一个先后顺序了，先打印的是存放相关的输出，再打印的取元素，如下：

而从输出的结果可以看到，存放元素的位置和取出元素的位置如预期，都是按着上一次的位置进行的，那如果咱们这样巅倒一下顺序呢？

 

再运行：

这次的输出就木有这么工整了，原因是由于在还木有元素的情况下先消费肯定会阻塞，所以：

接着就不继续细分析了，基本上就是按着上面说的原则进行执行的，好，下面继续来修改一下生产者与消费者的线程数，来对写的程序做做测试：

嗯，没啥问题，先生产了5个数据，然后再消费了5个，接下来再来修改：

结果：

put method: [hello, null, null, null, null, null, null, null, null, null]
put method: [hello, hello, null, null, null, null, null, null, null, null]
put method: [hello, hello, hello, null, null, null, null, null, null, null]
put method: [hello, hello, hello, hello, null, null, null, null, null, null]
put method: [hello, hello, hello, hello, hello, null, null, null, null, null]
put method: [hello, hello, hello, hello, hello, hello, null, null, null, null]
put method: [hello, hello, hello, hello, hello, hello, hello, null, null, null]
put method: [hello, hello, hello, hello, hello, hello, hello, hello, null, null]
put method: [hello, hello, hello, hello, hello, hello, hello, hello, hello, null]
put method: [hello, hello, hello, hello, hello, hello, hello, hello, hello, hello]
take method: [null, hello, hello, hello, hello, hello, hello, hello, hello, hello]
put method: [hello, hello, hello, hello, hello, hello, hello, hello, hello, hello]
take method: [hello, null, hello, hello, hello, hello, hello, hello, hello, hello]
put method: [hello, hello, hello, hello, hello, hello, hello, hello, hello, hello]
take method: [hello, hello, null, hello, hello, hello, hello, hello, hello, hello]
put method: [hello, hello, hello, hello, hello, hello, hello, hello, hello, hello]
take method: [hello, hello, hello, null, hello, hello, hello, hello, hello, hello]
take method: [hello, hello, hello, null, null, hello, hello, hello, hello, hello]
put method: [hello, hello, hello, hello, null, hello, hello, hello, hello, hello]
put method: [hello, hello, hello, hello, hello, hello, hello, hello, hello, hello]
take method: [hello, hello, hello, hello, hello, null, hello, hello, hello, hello]
put method: [hello, hello, hello, hello, hello, hello, hello, hello, hello, hello]
take method: [hello, hello, hello, hello, hello, hello, null, hello, hello, hello]
put method: [hello, hello, hello, hello, hello, hello, hello, hello, hello, hello]
take method: [hello, hello, hello, hello, hello, hello, hello, null, hello, hello]
put method: [hello, hello, hello, hello, hello, hello, hello, hello, hello, hello]
take method: [hello, hello, hello, hello, hello, hello, hello, hello, null, hello]
put method: [hello, hello, hello, hello, hello, hello, hello, hello, hello, hello]
take method: [hello, hello, hello, hello, hello, hello, hello, hello, hello, null]
put method: [hello, hello, hello, hello, hello, hello, hello, hello, hello, hello]
take method: [null, hello, hello, hello, hello, hello, hello, hello, hello, hello]
take method: [null, null, hello, hello, hello, hello, hello, hello, hello, hello]
take method: [null, null, null, hello, hello, hello, hello, hello, hello, hello]
take method: [null, null, null, null, hello, hello, hello, hello, hello, hello]
take method: [null, null, null, null, null, hello, hello, hello, hello, hello]
take method: [null, null, null, null, null, null, hello, hello, hello, hello]
take method: [null, null, null, null, null, null, null, hello, hello, hello]
take method: [null, null, null, null, null, null, null, null, hello, hello]
take method: [null, null, null, null, null, null, null, null, null, hello]
take method: [null, null, null, null, null, null, null, null, null, null]

Process finished with exit code 0

20个生产者与20个消费者执行完之后，最终肯定是把数组中的元素都给消费掉了，妥妥的。继续来修改程序进行测试：

那如果反过来呢？

运行：

以上就是关于Condition这个例子解析，说实话要实现这样一个功能并不是很简单的，但是消化好这个例子对于Condition的理解是非常好的。