java - 如何实现队列满了自动弹出先入项？

Question

这个问题已经有答案了:

Size-limited queue that holds last N elements in Java (9 个回答)

已关闭 8 年前。

我正在跟踪颜色列表。我只需要担心添加到此列表中的最后两种颜色。所以这个队列应该是固定大小(2)。

    queue.add(color1);
    queue.add(color2);
    queue.add(color3); //adding color3 should automatically remove color1 from the queue. 
    //So the queue should now only contain 'color2' and 'color3'

Java 是否有用于此类操作的内置 Collection？还是我需要自己构建它？

Answer 1

我想您可能正在寻找 CircularFifoQueue 来自 Apache Commons 4.x，它具有固定大小并默默地删除元素以为新元素腾出空间。这是来自文档:

CircularFifoQueue is a first-in first-out queue with a fixed size that replaces its oldest element if full.

The removal order of a CircularFifoQueue is based on the insertion order; elements are removed in the same order in which they were added. The iteration order is the same as the removal order.