Java模式在`ABC`中找到两组两个字母 [英] Java pattern to find two groups of two letters in `ABC`

问题描述

我有一个这样定义的模式：

I have a pattern defined like this:

 private static final Pattern PATTERN = Pattern.compile("[a-zA-Z]{2}");

在我的代码中，我这样做：

And in my code I'm doing this:

 Matcher matcher = PATTERN.matcher(myString);

并使用while循环查找所有匹配项。

and using a while loop to find all matches.

 while (matcher.find()){
 //do something here
 }

如果 myString 是 12345AB3CD45 匹配器正在找到那些两组两个字母（ AB 和 CD ）。问题是我有时 myString 为 12345ABC356 所以我希望匹配器找到，首先 AB 然后 BC （只找到'AB）。

If myString is 12345AB3CD45 the matcher is finding those two groups of two letters (AB and CD). The problem is that I have sometimes myString as 12345ABC356 so I would like the matcher to find, first AB and then BC (is only finding `AB).

Am我做错了或正则表达式错误或匹配器不能正常工作？

Am I doing this wrong or the regex is wrong or the matcher doesn't work this way?

推荐答案

放置的文本片段在组0中（整场比赛）不能在下一场比赛中重复使用，成为组0的一部分。

Fragment of text which was placed in group 0 (entire match) can't be reused in next match to be part of group 0.

12345ABC356
     ^^  - AB was placed in standard match (group 0)
      ^^ - B can't be reused here as part of standard match

您可以通过诸如预见，它不会消费匹配的部分（它们是零长度），但您可以将它们的内容放在单独的捕获组，您将可以访问它。

You can solve this problem with look-around mechanisms like look-ahead, which doesn't consume matched part (they are zero-length), but you can place their content in separate capturing group which you will be able to access.

所以您的代码可以看起来喜欢

So your code can look like

private static final Pattern PATTERN = Pattern.compile("[a-zA-Z](?=([a-zA-Z]))");
//                                                      ^^^^^^^^   ^^^^^^^^^^
//                                                       group 0    group 1

//...

Matcher matcher = PATTERN.matcher(myString);
while (matcher.find()){
    String match = matcher.group() + matcher.group(1);
    //...
}

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