时间戳

首页 > 解决方案 > How to write a regex capture group which matches a character 3 or 4 times before a delimiter?

java - How to write a regex capture group which matches a character 3 or 4 times before a delimiter?

问题描述

I'm trying to write a regex that splits elements out according to a delimiter. The regex also needs to ensure there are ideally 4, but at least 3 colons : in each match.

Here's an example string:

"Checkers, etc:Blue::C, Backgammon, I say:Green::Pepsi:P, Chess, misc:White:Coke:Florida:A, :::U"

From this, there should be 4 matches:

Here's what I've tried so far: 

([^:]*:[^:]*){3,4}(?:, )

Regex 101 at: https://regex101.com/r/O8iacP/8

I tried setting up a non-capturing group for ,

Then I tried matching a group of any character that's not a :, a :, and any character that's not a : 3 or 4 times.

The code I'm using to iterate over these groups is:

String line = "Checkers, etc:Blue::C, Backgammon, I say::Pepsi:P, Chess:White:Coke:Florida:A, :::U";
String pattern = "([^:]*:[^:]*){3,4}(?:, )";

  // Create a Pattern object
  Pattern r = Pattern.compile(pattern);

  // Now create matcher object.
  Matcher matcher = r.matcher(line);
  while (matcher.find()) {
        System.out.println(matcher.group(1));
    }

Any help is appreciated!

Edit

Using @Casimir's regex, it's working. I had to change the above code to use group(0) like this:

String line = "Checkers, etc:Blue::C, Backgammon, I say::Pepsi:P, Chess:White:Coke:Florida:A, :::U";
String pattern = "(?![\\s,])(?:[^:]*:){3}\\S*(?![^,])";

// Create a Pattern object
Pattern r = Pattern.compile(pattern);

// Now create matcher object.
Matcher matcher = r.matcher(line);
while (matcher.find()) {
    System.out.println(matcher.group(0));
}

Now prints:

Checkers, etc:Blue::C
Backgammon, I say::Pepsi:P
Chess:White:Coke:Florida:A
:::U

Thanks again!

标签： javaregexregex-group

解决方案

我建议这种模式：

(?![\\s,])(?:[^:]*:){3}\\S*(?![^,])

负前瞻避免匹配前导或尾随分隔符。第二个特别强制匹配后跟分隔符或字符串结尾（后面不跟不是逗号的字符）。

演示

请注意，该模式没有捕获组，因此结果是整个匹配（或组 0）。

推荐阅读