正则表达式检查字符串是否仅包含一个大写字母

Question

What is the regex to make sure that a given string contains exactly one uppercase letter? if the string contains more than one i dont want it to be matched.

• just 1 Uppercase character

I know the patterns for individual sets namely [az] , [AZ] , \d and _|[^\w] (I got them correct, didn't I?).

But how do I make them to match only with strings (in java) that only contains 1 uppercase?

Answer 1

You may use this regex with 2 negated character classes:

^[^A-Z]*[A-Z][^A-Z]*$

Above regex will support ASCII upper case letters only. If you want to match unicode letters then use:

^\P{Lu}*\p{Lu}\P{Lu}*$

RegEx Demo 2 RegEx Demo

Here:

• \P{Lu}* : Match 0 or more non-uppercase unicode letters
• \p{Lu} : Match an uppercase unicode letter