Regex匹配一个周期，但如果在任何一方(Java)中有一个周期，则不匹配。

I'm looking for a regex that will match a period character, ONLY if none of that period's surrounding characters are also periods.

我正在寻找一个与句号字符匹配的正则表达式，前提是那个时期的所有字符都不是句点。

 Fine by me... leave!    FAIL

 Okay.. You win.     SUCCEED

 Okay. SUCCEED //Note here, the period is the last char in the string.

I was thinking do:

我想做的事:

 [^\\.*]\\.

But that is just wrong and probably not at all in the right direction. I hope this question helps others in the same situation as well.

但这是错误的，很可能根本就不是正确的方向。我希望这个问题也能帮助同样处境的人。

Thanks.

谢谢。

3 个解决方案

#1

You need to wrap the dot in negative look arounds:

你需要把圆点包装成负面的外观:

(?<![.])[.](?![.])

I prefer [.] over \\., because:

我更喜欢[。在\ \]。,因为:

It's easier to read - there are too many back slashes in java literals already
它更容易阅读——java文字中已经有太多的反斜杠。
[.] looks a bit like an X wing fighter from Star Wars ™
(。看上去有点像一个X翼战斗机从星球大战™

#2

You can use negative look ahead and look behind or this alternative regex:

你可以用消极的眼光看前面，看看后面或者这个替代的regex:

String regex = "(^\\.[^\\.]|[^\\.]\\.[^\\.]|[^\\.]\\.$)";

The first alternative check the beginning ^ of the string (if it can start with a dot), the second looks for any dot inside and the third looks for a dot at the end of the string $.

第一个替代检查字符串的开始^(如果它可以从一个点开始),第二个查找任何点在第三个查找字符串的最后一个点美元。

#3

That regex will still match any period that isn't preceded by another period.

该regex仍将匹配任何不包含另一个周期的周期。

[^\.]\.[^\.] Takes care of both sides of the target period.

[^ \]\[^ \。在目标周期内兼顾双方。

EDIT: Java doesn't have a raw string like Python, so you would need full escapes: [^.]\\.[^.]|^\\.[^.]|[^.]\\.$

编辑:Java没有原始字符串像Python,所以你需要完全逃脱:[^]\ \[^]。| ^ \ \[^]。|[^]\ \ $

#1