前言
DelayQueue是BlockingQueue接口的实现类，它是带有延时性能的无界阻塞队列，意思就是每个元素都有过期工夫，当从队列获取元素时，只有过期元素才会出队列。队列的头部元素是最快要过期的元素。
实现原理
先来看看它的类构造：
public class DelayQueue<E extends Delayed> extends AbstractQueue<E> implements BlockingQueue<E> {}能够看到，寄存的元素必须实现了Delayed接口，它的定义如下：
public interface Delayed extends Comparable<Delayed> { long getDelay(TimeUnit unit);}再来看要害属性：
private final transient ReentrantLock lock = new ReentrantLock();private final PriorityQueue<E> q = new PriorityQueue<E>();private Thread leader = null;private final Condition available = lock.newCondition();再来看重要办法：
offer()
public boolean offer(E e) { final ReentrantLock lock = this.lock; lock.lock(); try { q.offer(e); if (q.peek() == e) { leader = null; available.signal(); } return true; } finally { lock.unlock(); }}poll()
public E poll() { final ReentrantLock lock = this.lock; lock.lock(); try { E first = q.peek(); if (first == null || first.getDelay(NANOSECONDS) > 0) return null; else return q.poll(); } finally { lock.unlock(); }}take()
public E take() throws InterruptedException { final ReentrantLock lock = this.lock; lock.lockInterruptibly(); try { for (;;) { E first = q.peek(); if (first == null) available.await(); else { long delay = first.getDelay(NANOSECONDS); if (delay <= 0) return q.poll(); first = null; // don't retain ref while waiting if (leader != null) available.await(); else { Thread thisThread = Thread.currentThread(); leader = thisThread; try { available.awaitNanos(delay); } finally { if (leader == thisThread) leader = null; } } } } } finally { if (leader == null && q.peek() != null) available.signal(); lock.unlock(); }}今天再剖析吧，先睡了，晚安全世界！