包含至少 4 个唯一可打印 ASCII 字符（不包括少数特殊字符）的字符串的正则表达式

Question

I am working on an application, in which input strings must have following properties:

• Contains at least 4 unique characters
• Doesn't contain non-printable ASCII characters
• Doesn't contain comma (,), colon (:), equals sign (=), or space

I came up with below regex, which matches strings with at least 4 unique chars, and all printable ASCII chars excluding space.

^([!-~]+)((?!\1)[!-~]+)((?!\1|\2)[!-~]+)((?!\1|\2|\3)[!-~]+)$

How do I modify it to exclude comma (,), colon (:), equals sign (=)?

Answer 1

In Java you can make use of Character Class Subtraction .

The range can look like [!-~&&[^,:=]]

^([!-~&&[^,:=]]+)((?!\1)[!-~&&[^,:=]]+)((?!\1|\2)[!-~&&[^,:=]]+)((?!\1|\2|\3)[!-~&&[^,:=]]+)$

In Java:

String regex = "^([!-~&&[^,:=]]+)((?!\\1)[!-~&&[^,:=]]+)((?!\\1|\\2)[!-~&&[^,:=]]+)((?!\\1|\\2|\\3)[!-~&&[^,:=]]+)$";

Regex demo