System.out.println和System.err.println出现故障 [英] System.out.println and System.err.println out of order

问题描述

我的System.out.println()和System.err.println()调用没有按照我创建的顺序打印到控制台.

My System.out.println() and System.err.println() calls aren't being printed to the console in the order I make them.

public static void main(String[] args) {
    for (int i = 0; i < 5; i++) {
        System.out.println("out");
        System.err.println("err");
    }
}

这将产生:

out
out
out
out
out
err
err
err
err
err

代替交替使用out和err.为什么会这样?

Instead of alternating out and err. Why is this?

推荐答案

它们是不同的流，并在不同的时间刷新.

They are different streams and are flushed at different times.

如果您输入

System.out.flush();
System.err.flush();

在您的循环内，它将按预期工作.

inside your loop, it will work as expected.

为澄清起见，将对输出流进行缓存，以便所有写入均进入此内存缓冲区.经过一段时间的安静之后，它们实际上已被写出.

To clarify, output streams are cached so all the write goes into this memory buffer. After a period of quiet, they are actually written out.

您写入两个缓冲区，然后在一段时间不活动后将它们都刷新(一个接一个).

You write to two buffers, then after a period of inactivity they both are flushed (one after the other).

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