ConcurrentLinkedDeque与LinkedBlockingDeque [英] ConcurrentLinkedDeque vs LinkedBlockingDeque

问题描述

我需要具有线程安全的LIFO结构，并发现可以为此使用Deque的线程安全实现. Java 7引入了 ConcurrentLinkedDeque 并且Java 6具有 LinkedBlockingDeque .

I need to have a thread-safe LIFO structure and found that I can use thread-safe implementations of Deque for this. Java 7 has introduced ConcurrentLinkedDeque and Java 6 has LinkedBlockingDeque.

如果我只使用LinkedBlockingDeque中的非阻塞方法，例如addFirst()和removeFirst()，它与ConcurrentLinkedDeque有什么区别吗?

If I were to use only the non-blocking methods in LinkedBlockingDeque such as addFirst() and removeFirst() does it have any difference to ConcurrentLinkedDeque?

即如果不考虑阻塞方面，除了LinkedBlockingDeque受限制之外，ConcurrentLinkedDeque和LinkedBlockingDeque之间还有其他区别吗?

i.e. If you disregard the blocking aspect, is there any other difference between ConcurrentLinkedDeque and LinkedBlockingDeque, apart from LinkedBlockingDeque being bounded?

推荐答案

两件事:

1::如果我仅使用LinkedBlockingDeque中的非阻塞方法，例如addFirst()和removeFirst()，它与ConcurrentLinkedDeque有什么区别吗?

1: If I were to use only the non-blocking methods in LinkedBlockingDeque such as addFirst() and removeFirst() does it have any difference to ConcurrentLinkedDeque?

在LinkedBlockingDeque中，这些方法在并发锁定行为方面确实有所不同:

These methods do have difference in terms of concurrent locking behavior, in LinkedBlockingDeque:

public E removeFirst() {
        E x = pollFirst();
        ..
    }
 public E pollFirst() {
        lock.lock(); //Common lock for while list
        try {
            return unlinkFirst();
        } finally {
            lock.unlock();
        }
    }

与addFirst方法类似.在ConcurrentLinkedDeque中，这两种方法的锁定行为都不同，并且效率更高，因为它不会锁定整个列表，而是锁定它的一部分，检查ConcurrentLinkedDeque的源将使您对此更加清楚.

Similarly for addFirst method. In ConcurrentLinkedDeque this locking behavior for both the method is different and is more efficient as it doesn't lock the whole list but a subset of it, checking source for ConcurrentLinkedDeque will give you more clarity on this.

2 :来自ConcurrentLinkedDeque的javadoc:

2: From javadoc of ConcurrentLinkedDeque:

请注意，与大多数集合不同的是，size方法不是 恒定时间操作.

Beware that, unlike in most collections, the size method is NOT a constant-time operation.

..

此外，批量操作addAll，removeAll，retainAll， 不保证可以执行containsAll，equals和toArray 原子地.

Additionally, the bulk operations addAll, removeAll, retainAll, containsAll, equals, and toArray are not guaranteed to be performed atomically.

以上对于LinkedBlockingDeque

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