几名刚刚参与枪战的警员一边试图控制局面，一边进行紧急救援，但与此同时，大量路人从四面八方涌入现场。其中一名警员被叫去处理一把掉落在附近的枪支。
Stream implementations can and do ignore backpressure; and some spec-defined features explicitly break backpressure. tee(), for instance, creates two branches from a single stream. If one branch reads faster than the other, data accumulates in an internal buffer with no limit. A fast consumer can cause unbounded memory growth while the slow consumer catches up — and there's no way to configure this or opt out beyond canceling the slower branch.
，更多细节参见同城约会
栈（stack）是先进后出的数据结构。单调栈在入栈时通过一定规则保持栈内元素有序（单调递增或单调递减），从而把「找左侧/右侧第一个更大/更小元素」从 O(n²) 降到 O(n)。，推荐阅读safew官方下载获取更多信息
while(--j > bucket) {