有界，自动丢弃，非阻塞，并发收集 [英] Bounded, auto-discarding, non-blocking, concurrent collection

问题描述

我在寻找一个集合：

• 是 Deque / 列表 - 即支持在顶部插入元素（最新项目到顶部） - deque.addFirst（..） / list.add（0，..）。它可以是 Queue ，但是迭代顺序应该是相反的 - 即最近添加的项目应该优先。


• - 即限制为20个项目


• 在达到容量时自动舍弃最旧的项目（位于底部的项目，最先添加）


• 非阻塞 - 如果deque是空的，检索不应该阻塞。


• 并发 - 多个线程应该能够对其进行操作

• is a Deque/List - i.e. supports inserting elements at "the top" (newest items go to the top) - deque.addFirst(..) / list.add(0, ..). It could be a Queue, but the iteration order should be reverse - i.e. the most recently added items should come first.
• is bounded - i.e. has a limit of 20 items
• auto-discards the oldest items (those "at the bottom", added first) when the capacity is reached
• non-blocking - if the deque is empty, retrievals should not block. It should also not block / return false / null / throw exception is the deque is full.
• concurrent - multiple threads should be able to operate on it

我可以使用 LinkedBlockingDeque 并将其包装到我的自定义集合中， code>操作检查大小并丢弃最后一个项目。

I can take LinkedBlockingDeque and wrap it into my custom collection that, on add operations checks the size and discards the last item(s). Is there a better option?

推荐答案

我做了这个简单的实现：

I made this simple imeplementation:

public class AutoDiscardingDeque<E> extends LinkedBlockingDeque<E> {

    public AutoDiscardingDeque() {
        super();
    }

    public AutoDiscardingDeque(int capacity) {
        super(capacity);
    }

    @Override
    public synchronized boolean offerFirst(E e) {
        if (remainingCapacity() == 0) {
            removeLast();
        }
        super.offerFirst(e);
        return true;
    }
}

对于我的需要这足够了，不同于 addFirst / offerFirst 的文档方法仍然遵循阻塞deque的语义。

For my needs this suffices, but it should be well-documented methods different than addFirst / offerFirst are still following the semantics of a blocking deque.

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