ConcurrentLinkedQueue
特点
- 容器无大小
- 单向队列
方法
-
poll()获取最后一个并删除
public E poll() {
restartFromHead:
for (;;) {
for (Node<E> h = head, p = h, q;;) {
E item = p.item;
if (item != null && p.casItem(item, null)) {
//成功的ca是线性化点
//从这个队列中删除项目
if (p != h) // hop two nodes at a time
updateHead(h, ((q = p.next) != null) ? q : p);
return item;
}
else if ((q = p.next) == null) {
updateHead(h, p);
return null;
}
else if (p == q)
continue restartFromHead;
else
p = q;
}
}
}
-
peek()只是偷窥，不删除数据
public E peek() {
restartFromHead:
for (;;) {
for (Node<E> h = head, p = h, q;;) {
E item = p.item;
if (item != null || (q = p.next) == null) {
updateHead(h, p);
return item;
}
else if (p == q)
continue restartFromHead;
else
p = q;
}
}
}
- offer() 在容器尾部插入，成功返回true
ConcurrentLinkedDeque
特点
- 双端队列，可以在头/尾拿、添加
- 其他跟
ConcurrentLinkedQueue一样
ArrayBlockingQueue
特点
- 容器初始要设置大小，超出异常（
throw new IllegalStateException("Queue full")）
/**
* Creates an {@code ArrayBlockingQueue} with the given (fixed)
* capacity and default access policy.
*
* @param capacity the capacity of this queue
* @throws IllegalArgumentException if {@code capacity < 1}
*/
public ArrayBlockingQueue(int capacity) {
this(capacity, false);
}
- 可以设置公平锁,默认不公平
/**
* Creates an {@code ArrayBlockingQueue} with the given (fixed)
* capacity and the specified access policy.
*
* @param capacity the capacity of this queue
* @param fair if {@code true} then queue accesses for threads blocked
* on insertion or removal, are processed in FIFO order;
* if {@code false} the access order is unspecified.
* @throws IllegalArgumentException if {@code capacity < 1}
*/
public ArrayBlockingQueue(int capacity, boolean fair) {
if (capacity <= 0)
throw new IllegalArgumentException();
this.items = new Object[capacity];
lock = new ReentrantLock(fair); //设置锁的公平
notEmpty = lock.newCondition();
notFull = lock.newCondition();
}
方法
-
offer()给容器添加数据，容器满时不会异常，只会返回true/flase -
add()给容器添加数据，容器满时会异常， -
put容器满了就阻塞
DelayQueue
特点
- 按照时间排序进/出(时间短的先出)
- 类实现delayed接口
TransferQueue
特点
- 数据不进入容器、直接给消费者，速度会更快
- transfer()时，没有消费者线程会阻塞
SynchronousQueue
特点
- 容器为0,也就是不能调用add()方法
- 必须消费,也就是put()方法一直阻塞，直到消费者消费
- 内部也是使用TransferQueue
/**
* Adds the specified element to this queue, waiting if necessary for
* another thread to receive it.
*
* @throws InterruptedException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
*/
public void put(E e) throws InterruptedException {
if (e == null) throw new NullPointerException();
//立即转让，失败后异常
if (transferer.transfer(e, false, 0) == null) {
Thread.interrupted();
throw new InterruptedException();
}
}
总结
阻塞队列
-
BlockingQueue 下的
- ArrayBlockingQueue
- LinkedBlockingQueue
- TransferQueue
- SynchronousQueue
DelayQueue
源码：github 欢迎各位同学指出问题/建议
