英文:
regular expression to match certian special chars in middle
问题
我正在尝试构建符合以下条件的Java正则表达式：
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标识符不得以特殊字符开头或结尾。
-
不允许出现多个连续的特殊字符序列。
-
允许的特殊字符包括：冒号、连字符（减号）、句号（句号）和下划线。
我已经进行了一些分析并构建了正则表达式：
String regularexp = "^[A-Za-z0-9](?:,/-/_.*?[^A-Za-z0-9]{2}).*?[A-Za-z0-9]$";
但不知何故它不起作用。
final Pattern pattern = Pattern.compile(regex);final Matcher matcher = pattern.matcher(string);while (matcher.find()) {System.out.println("完全匹配：" + matcher.group(0));for (int i = 1; i <= matcher.groupCount(); i++) {System.out.println("第 " + i + " 组：" + matcher.group(i));}}
请帮我检查一下我在哪里出错了。
英文:
i am trying to build java regular expression with following conditions:
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The identifier may not start or end with a special character
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sequences of multiple special characters are not permitted
-
permitted special characters are : colon,hyphen(minus),period(full stop) and underscore
i have done some analysis and built the regular expression :
String regularexp="^[A-Za-z0-9](?:,/-/_.*?[^A-Za-z0-9]{2}).*?[A-Za-z0-9]$" ;but somehow its not working .
final Pattern pattern = Pattern.compile(regex);final Matcher matcher = pattern.matcher(string);while (matcher.find()) {System.out.println("Full match: " + matcher.group(0));for (int i = 1; i <= matcher.groupCount(); i++) {System.out.println("Group " + i + ": " + matcher.group(i));}}
can you please check where i am doing mistake.
答案1
得分: 1
以下是翻译好的内容：
更容易编写的方法是，如果你专注于那些不是特殊字符的部分。那么字符串看起来像这样（在EBNF表示法中）：
<word> (<special-char> <word>)*
<word>是一个包含一个或多个字母数字字符的序列：[A-Za-z0-9]+。
通过要求<word>不为空，我们确保不会出现多个<special-char>的序列。- 而
<special-char>则恰好是一个特殊字符：[-:._]。
我把-放在第一位，这样我们就不需要转义它。
组合起来：
^[A-Za-z0-9]+([-:._][A-Za-z0-9]+)*$
英文:
It's easier to write if you focus on the parts that are not special characters. Then the string looks like this (in EBNF notation):
<word> (<special-char> <word>)*
<word>is a sequence of one or more alphanumeric characters:[A-Za-z0-9]+.
By requiring that a<word>is not empty, we guarantee that no
sequences of more than one<special-char>can occur.- And
<special-char>is exactly one special character:[-:._].
I put-first so we don't need to escape it.
Putting it together:
^[A-Za-z0-9]+([-:._][A-Za-z0-9]+)*$
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