put操作获取ReentrantLock独占锁
如果队列满,则调用notFull.await()
notFull是ReentrantLock的一个Condition 该线程会一直阻塞
那么什么时候会被释放呢?
public void put(E e) throws InterruptedException {
checkNotNull(e);
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
while (count == items.length)
//队列满 阻塞在notFull这个Condition上,当条件满足时会被唤醒
notFull.await();
enqueue(e);
} finally {
lock.unlock();
}
}
我们追踪notFull这个Condition,发现它是在dequeue 出队这个私有方法中唤醒的
每次有元素出队 都会试图唤醒等待在Condition中的put线程
private E dequeue() {
// assert lock.getHoldCount() == 1;
// assert items[takeIndex] != null;
final Object[] items = this.items;
@SuppressWarnings("unchecked")
E x = (E) items[takeIndex];
items[takeIndex] = null;
if (++takeIndex == items.length)
takeIndex = 0;
count--;
if (itrs != null)
itrs.elementDequeued();
//元素移除,notFull条件达成 唤醒阻塞线程
notFull.signal();
return x;
}