具有可变组数的正则表达式? [英] Regular expression with variable number of groups?

问题描述

是否可以创建具有可变组数的正则表达式?

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

例如在运行此之后...

After running this for instance...

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

...我想要类似的东西

... I would like to have something like

• 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.)

正如@Tim Pietzcker 在评论中指出的那样，perl6 和 .NET 有这个功能.

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:

与一个关联的捕获输入group 总是子序列最近匹配的组.如果一个组被第二次评估因为量化，那么它的先前捕获的值，如果有的话，如果第二个将被保留评估失败.匹配字符串"aba" 反对表达式 (a(b)?)+,例如，将第二组设置为乙".所有捕获的输入都被丢弃在每场比赛开始时.

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)

这篇关于具有可变组数的正则表达式?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！