java System.lineSeparator() 不返回任何内容
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System.lineSeparator() returns nothing
提问by Gero
What should I see when I use the following?
当我使用以下内容时，我应该看到什么？
System.out.println("LineSeperator1: "+System.getProperty("line.separator"));
System.out.println("LineSeperator2: "+System.lineSeparator());
I get the following back:
我得到以下回复：
LineSeperator1:
LineSeperator2:
Is it empty? invisible? shouldn there be something like \r or \n?
是空的吗？无形的？应该有类似的东西\r or \n吗？
I use windows 7, eclipse and jdk 1.8.
我使用 windows 7、eclipse 和 jdk 1.8。
回答by Alden
As you expect, the line separator contains special characters such as '\r'or '\n'that denote the end of a line. However, although they would be written in Java source code with those backslash escape sequences, they do not appear that way when printed. The purpose of a line separator is to separate lines, so, for example, the output of
如您所料，行分隔符包含特殊字符，例如'\r'或'\n'表示行尾。然而，尽管它们是用 Java 源代码编写的，带有那些反斜杠转义序列，但在打印时它们不会那样显示。行分隔符的目的是分隔行，例如，输出
System.out.println("Hello"+System.lineSeparator()+"World");
is
是
Hello
World
rather than, say
而不是说
Hello\nWorld
You can even see this in the output of your code: the output of
您甚至可以在代码的输出中看到这一点：
System.out.println("LineSeperator1: "+System.getProperty("line.separator"));
had an extra blank line before the output of the next statement, because there was a line separator from System.getProperty("line.separator")and another from the use of println.
在下一条语句的输出之前有一个额外的空行，因为有一个行分隔符 fromSystem.getProperty("line.separator")和另一个 from 的使用println。
If you really want to see what the escaped versions of the line separators look like, you can use escapeJavafrom Apache Commons. For example:
如果您真的想查看行分隔符的转义版本是什么样的，您可以使用escapeJavafrom Apache Commons。例如：
import org.apache.commons.lang3.StringEscapeUtils;
public class LineSeparators {
public static void main(String[] args) {
String ls1 = StringEscapeUtils.escapeJava(System.getProperty("line.separator"));
System.out.println("LineSeperator1: "+ls1);
String ls2 = StringEscapeUtils.escapeJava(System.lineSeparator());
System.out.println("LineSeperator2: "+ls2);
}
}
On my system, this outputs
在我的系统上，这输出
LineSeparator1: \n
LineSeparator2: \n
Note that I had to run it in the same folder as the .jar file from the Apache download, compiling and running with these commands
请注意，我必须在与Apache 下载的 .jar 文件相同的文件夹中运行它，使用这些命令编译和运行
javac -cp commons-lang3-3.4.jar LineSeparators.java
java -cp commons-lang3-3.4.jar:. LineSeparators
回答by weston
Printing something afterwards will show the effect:
之后打印一些东西会显示效果：
System.out.println("a" + System.lineSeparator() + "b");
Gives
给
a
b
