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

Question

我对Java很新颖。

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

当试图验证码：

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？ 不应该最后打印。

我 “%n” 试图在最后& System.err.flush()这样的：

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"); 

还是相同的输出。

Answer 1

你是不是调用println()电话和System.out和System.err之间flush()都（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");