11.BlockingDeque

BlockingDeque定义了一个阻塞的双端队列接口。

public interface BlockingDeque<E> extends BlockingQueue<E>, Deque<E> { 
    void putFirst(E e) throws InterruptedException; 
    void putLast(E e) throws InterruptedException; 
    E takeFirst() throws InterruptedException; 
    E takeLast() throws InterruptedException; 
    // ... 
}

该接口继承了BlockingQueue接口，同时增加了对应的双端队列操作接口。该接口只有一个实现，就是LinkedBlockingDeque。
核心数据结构是一个双向链表

LinkedBlockingDeque

public class LinkedBlockingDeque<E> extends AbstractQueue<E> implements BlockingDeque<E>, java.io.Serializable {
     static final class Node<E> {
         E item; 
        Node<E> prev; // 双向链表的Node 
        Node<E> next;
        Node(E x) { item = x; 
        } 
    }
    transient Node<E> first; // 队列的头和尾 
    transient Node<E> last; 
    private transient int count; // 元素个数 
    private final int capacity; // 容量 
    // 一把锁+两个条件 
    final ReentrantLock lock = new ReentrantLock(); 
    private final Condition notEmpty = lock.netCondition(); 
    private final Condition notFull = lock.newCondition();
}