public E take() throws InterruptedException {    E x;    int c = -1;    final AtomicInteger count = this.count; //队列中元素数量    final ReentrantLock takeLock = this.takeLock; // 拿东西的锁    takeLock.lockInterruptibly();    try {        while (count.get() == 0) {            notEmpty.await(); // notEmpty这个条件不成立 进入等待        }        x = dequeue(); // 出栈        // 例子：count = 1 --> c = count.getAndDecrement() --> c = 1 count = 0        c = count.getAndDecrement(); // getAndDecrement表示获取当前值然后减一          if (c > 1)            notEmpty.signal(); // 元素数量至少两个 所以这里可以唤醒一个await的线程    } finally {        takeLock.unlock();    }    if (c == capacity)        signalNotFull();    return x;}

当线程调用了notEmpty.await();进入等待之后  会有别的线程获取到takeLock锁进来

如果count.get()也等于0也会等待  会又有线程拿到takeLock锁

lockInterruptibly和lock区别

例子 

测试线程拿到ReentrantLock锁后调用了Condition的await后  会不会有新的线程拿到锁

package blockingqueue;import java.util.ArrayDeque;import java.util.Queue;import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.ReentrantLock;/** * Created by User on 2017/12/21. */public class App {    ReentrantLock lock = new ReentrantLock();    Condition cannotEmpty = lock.newCondition();    Queue queue = new ArrayDeque();    public static void main(String[] args) {        App app = new App();        new Thread(()->{            for (;;) {                app.queue.add(new Object());                System.out.println("添加了一个产品");                try {                    Thread.sleep(3000);                } catch (InterruptedException e) {                    e.printStackTrace();                }                app.lock.lock();                app.cannotEmpty.signal();                app.lock.unlock();            }        }).start();        for (int i = 0; i < 5; i++) {            new Thread(()->{                try {                    for (;;) app.consume();                } catch (InterruptedException e) {                    e.printStackTrace();                }            }).start();        }    }    private void consume() throws InterruptedException {        lock.lock();        try {            System.out.println("进来一个消费者");            while (queue.size() == 0) {                cannotEmpty.await();            }            System.out.println("开始消费");            Thread.sleep(1000);            queue.poll();            System.out.println("消费结束");            if (queue.size() > 0) cannotEmpty.signal();        } finally {            lock.unlock();        }    }}