英文:
regex - Uppercase letters followed by any utf-8 lowercase characters
问题
private static String pattern = "^\u0049\u004A(\p{Ll})*";
System.out.println(Pattern.compile(pattern).matcher("IJP").find()); // true
I am using this regex but it doesn't seem to work. For "IJP" it should not match as P is uppercase.
英文:
I want to write a regex which is valid if it starts with IJ followed by any lowercase letters in utf-8.
private static String pattern = "^\\u0049\\u004A(\\p{Ll})*";
System.out.println(Pattern.compile(pattern).matcher("IJP").find()); // true
I am using this regex but it doesn't seem to work. For "IJP" it should not match as P is uppercase.
答案1
得分: 1
你的模式应该是：
final String pattern = "^\\u0049\\u004A\\p{Ll}*$";
注意在结尾处放置 $ 以使其在结尾之前匹配 0 个或多个小写字符。请注意，我已经删除了 \p{Ll} 周围不必要的分组。
代码演示：
jshell> String pattern = "^\\u0049\\u004A\\p{Ll}*$";
pattern ==> "^\\u0049\\u004A\\p{Ll}*$"
jshell> Pattern.compile(pattern).matcher("IJP").find();
$6 ==> false
英文:
Your pattern should be:
final String pattern = "^\\u0049\\u004A\\p{Ll}*$";
Note placement of $ in the end to make it 0 or more lowercase characters before end. Note that I have removed unnecessary group around \p{Ll}.
Code Demo:
jshell> String pattern = "^\\u0049\\u004A\\p{Ll}*$";
pattern ==> "^\\u0049\\u004A\\p{Ll}*$"
jshell> Pattern.compile(pattern).matcher("IJP").find();
$6 ==> false
答案2
得分: 0
\\u0049 是表示 I 的一种相当晦涩的方式，你不觉得是吗？为什么不直接写 pattern = "^IJ\\p{Ll}" 呢？
不过 IJP 确实会匹配。想想看。你要求一个 I，然后是一个 J，然后是 0 个或更多小写字母。这就是：一个 I，一个 J，和 0 个小写字母。
你可以使用 matches() 替代 find()（它会问：整个字符串是否与正则表达式完全匹配，而不是'是否存在某个子字符串与之匹配'），或者，既然你已经在那里加入了 ^，可以在末尾加上 $ 进行匹配。
英文:
\\u0049 is a rather obtuse way of writing I, don't you think? Why not just... write pattern = "^IJ\\p{Ll}"?
IJP does match though. Think about it. You're asking for an I, then a J, then 0 or more lowercase letters. Which is right there: An I, a J, and 0 lowercase letters.
Either use matches() instead of find() (which asks: Does the ENTIRE string match the regexp, vs. 'is there some substring that does') or, as you've already thrown the ^ in there, toss a $ at the end to match.
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