识别正则表达式模式中的捕获组 [英] Identifying capture groups in a Regex Pattern

问题描述

Java中是否有一种方法(也许带有附加的开源库)来标识 java.util.regex.Pattern 中的捕获组(即，在创建Matcher之前)

Is there a way in Java (perhaps with an additional Open Source library) to identify the capture groups in a java.util.regex.Pattern (i.e. before creating a Matcher)

Java文档中的示例:

Example from the Java docs:

捕获组编号为数他们的开括号从左到右.在表达中(((A)(B(C))))，例如四个这样的组:

Capturing groups are numbered by counting their opening parentheses from left to right. In the expression ((A)(B(C))), for example, there are four such groups:

1         ((A)(B(C)))
2         (A)
3         (B(C))
4         (C)

原则上，应该可以从(已编译的)模式中识别出这些.

In principle it should be possible to identify these from the (compiled) Pattern.

更新:从@Leniel和eslewhere来看，该功能(命名组")似乎将在2011年中期出现在Java 7中.如果我迫不及待，可以使用jregex，尽管我不太确定API是什么.

UPDATE: From @Leniel and eslewhere it seems that this facility ("named groups") will be present in Java 7 in mid 2011. If I can't wait for that I can use jregex although I'm not quite sure what the API is.

推荐答案

您可以通过创建虚拟Matcher来找出组的数量，如下所示:

You can find out the number of groups by creating a dummy Matcher, like so:

Pattern p = Pattern.compile("((A)(B(C)))");
System.out.println(p.matcher("").groupCount());

如果您想要实际的子表达式(((A)(B(C)))，(A)等)，则否，该信息是不可用.

If you want the actual subexpressions (((A)(B(C))), (A), etc.), then no, that information is not available.

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