在Java中要运行多少个线程? [英] how many threads to run in java?

问题描述

我有一个绝妙的主意，可以加快生成36个文件所需的时间:使用36个线程！不幸的是，如果我使用36个线程/会话启动一个连接(一个j2ssh连接对象)，则与每次执行每个线程相比，所有事情的滞后时间都更大.
现在，如果我尝试创建36个新连接(36个j2ssh连接对象)，则每个线程都具有到服务器的单独连接，要么我内存不足异常(以某种方式程序仍然运行，并成功结束其工作，但速度比我一个接一个执行另一个线程的时间).

I had this brilliant idea to speed up the time needed for generating 36 files: use 36 threads!! Unfortunately if I start one connection (one j2ssh connection object) with 36 threads/sessions, everything lags way more than if I execute each thread at a time.
Now if I try to create 36 new connections (36 j2ssh connection objects) then each thread has a separate connection to server, either i get out of memory exception (somehow the program still runs, and successfully ends its work, slower than the time when I execute one thread after another).

那该怎么办?如何找到我应该使用的最佳线程号? 因为Thread.activeCount()在启动我的36个线程之前是3?我正在使用联想笔记本电脑英特尔酷睿i5.

So what to do? how to find the optimal thread number I should use? because Thread.activeCount() is 3 before starting mine 36 threads?! i'm using Lenovo laptop Intel core i5.

推荐答案

您可以使用ExecutorService将其范围缩小到更合理的线程数.您可能想使用接近可用处理器核心数量的东西，例如:

You could narrow it down to a more reasonable number of threads with an ExecutorService. You probably want to use something near the number of processor cores available, e.g:

int threads = Runtime.getRuntime().availableProcessors();
ExecutorService service = Executors.newFixedThreadPool(threads);
for (int i = 0; i < 36; i++) {
    service.execute(new Runnable() {
        public void run() {
            // do what you need per file here
        }
    });
}
service.shutdown();

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