具有可变数量的组的正则表达式？ [英] Regular expression with variable number of groups?

问题描述

是否可以创建一个包含可变数量的组的正则表达式？

Is it possible to create a regular expression with a variable number of groups?

例如，运行后...

Pattern p = Pattern.compile("ab([cd])*ef");
Matcher m = p.matcher("abcddcef");
m.matches();

...我想要像

• m.group（1） = c


• m.group（2） = d


• m.group（3） = d


• m.group（4） = c。

• m.group(1) = "c"
• m.group(2) = "d"
• m.group(3) = "d"
• m.group(4) = "c".

（背景：我正在解析一些数据行，其中一个字段正在重复。我想避免这些字段的 matcher.find 循环。）

(Background: I'm parsing some lines of data, and one of the "fields" is repeating. I would like to avoid a matcher.find loop for these fields.)

As @Tim Pietzcker在评论中指出， perl6 和 .NET 具有此功能。

As pointed out by @Tim Pietzcker in the comments, perl6 and .NET have this feature.

推荐答案

根据文档，Java正则表达式不能这样做：

According to the documentation, Java regular expressions can't do this:

与
组关联的捕获输入始终是
组最近匹配的子序列。如果
组由于量化而第二次评估
，那么如果第二次
评估失败，则其b $ b先前捕获的值（如果有）
将被保留。将字符串
aba与表达式（a（b）？）+，
匹配，例如，将第二组设置为
b。所有捕获的输入在每场比赛开始时被丢弃
。

The captured input associated with a group is always the subsequence that the group most recently matched. If a group is evaluated a second time because of quantification then its previously-captured value, if any, will be retained if the second evaluation fails. Matching the string "aba" against the expression (a(b)?)+, for example, leaves group two set to "b". All captured input is discarded at the beginning of each match.

（强调添加）

这篇关于具有可变数量的组的正则表达式？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！