java - 收集队列

Question

如果我想自定义队列的实现，正确的是说我可以选择我想要的任何顺序(不是 FIFO)，但我必须始终尊重要删除的元素定位为“head”的事实吗？

但对于插入操作，我没有义务将元素放在尾部(例如放入 FIFO 中)？

Answer 1

你是对的。 javadoc明确指出这一点:

Queues typically, but do not necessarily, order elements in a FIFO (first-in-first-out) manner. Among the exceptions are priority queues, which order elements according to a supplied comparator, or the elements' natural ordering, and LIFO queues (or stacks) which order the elements LIFO (last-in-first-out). Whatever the ordering used, the head of the queue is that element which would be removed by a call to remove() or poll(). In a FIFO queue, all new elements are inserted at the tail of the queue. Other kinds of queues may use different placement rules. Every Queue implementation must specify its ordering properties.