带有'%n'的Java'System.err.format'后跟'System.out.println',println打印在中间

Question

我是Java的新手.

我使用的是Ubuntu 16.04,JDK 8u101,Netbeans8.1.

尝试此代码时:

public static void main(String[] args) {
    System.err.format("1st Line %nPrints At 3rd Line,Shouldn't this be In 2nd Line ");
    System.out.println("Shouldn't this be the third line,prints at 2nd line");
}

输出是:

This Prints At 1st Line 
Shouldn't this be the third line, but prints at 2nd line
This Prints At 3rd Line, Shouldn't this be In 2nd Line

为什么" System.out.println"打印在中间？不应该打印最后.

我最后尝试了" %n"并且System.err.flush()像这样:

System.err.format("1st Line %nPrints At 3rd Line,Shouldn't this be In 2nd Line%n");
System.err.flush();
System.out.println("Shouldn't this be the third line,prints at 2nd line");

还是输出相同.

Answer 1

你是不是调用flush()之间println()的调用和System.out和System.err均(独立)缓冲PrintStream(S).

// and you need a %n on the end to make 3 lines.
System.err.format("1st Line %nPrints At 3rd Line,Shouldn't this be In 2nd Line%n"); 
System.err.flush(); // <-- only needed if the previous write doesn't have
                    //     an implicit flush(); newline (%n) does.
System.out.println("Shouldn't this be the third line,prints at 2nd line");