peek方法和remove方法实现代码

    public E peek() {
        if (count.get() == 0)
            return null;
        final ReentrantLock takeLock = this.takeLock;
        takeLock.lock();
        try {
            Node<E> first = head.next;
            if (first == null)
                return null;
            else
                return first.item;
        } finally {
            takeLock.unlock();
        }
    }

    public boolean remove(Object o) {
        if (o == null) return false;
        fullyLock();//获取存元素锁和取元素锁（不允许存或取元素），因为有可能同时涉及到头尾结点的访问问题
        try {
            for (Node<E> trail = head, p = trail.next; p != null; trail = p, p = p.next) {// 遍历整个链表
                if (o.equals(p.item)) {// 结点的值与指定值相等
                    unlink(p, trail); // 断开结点
                    return true;
                }
            }
            return false;
        } finally {
            fullyUnlock();
        }
    }

    void unlink(Node<E> p, Node<E> trail) {
        p.item = null; 
        trail.next = p.next;// 断开p结点
        if (last == p) // 尾节点为p结点
            last = trail; // 重新赋值尾节点
        if (count.getAndDecrement() == capacity)
            notFull.signal();
    }

    void fullyLock() {
        putLock.lock();
        takeLock.lock();
    }

    void fullyUnlock() {
        takeLock.unlock();
        putLock.unlock();
    }