Matt Zdj :
I try to have a regex validating an input field.
This question is the continuation of this question but I made a mistake and the question changed a bit so I created a new one.
Here is my java regex :
^(?:\?*[a-zA-Z\d]){2}[a-zA-Z\d?]*\*?$
What I'm tying to match is :
- Minimum 2 alpha-numeric characters (other than '?' and '*')
- The '*' can only appears one time and at the end of the string
- The '?' can appears multiple time
- No WhiteSpace right at the beginning
- No WhiteSpace before or after '?' or '*'
So for exemple :
- abcd = OK
- ?bcd = OK
- ab?? = OK
- ab*= OK
- ab?* = OK
- ??cd = OK
- ab cd = OK
- *ab = NOT OK
- a ? b =NOT OK
- ??? = NOT OK
- ab? cd = NOT OK
- ab ?d = NOT OK
- ab * = NOT OK
- abcd = NOT OK (space at the begining)
As i've asked in the fisrt question, no white space at all are allowed in my regex now but that's not what I want and I'm a bit lost can you help me please?
Wiktor Stribiżew :
You may use
^(?!\s)(?!.*\s[*?])(?!.*[*?]\s)(?:[?\s]*[a-zA-Z0-9]){2}[a-zA-Z0-9?\s]*\*?$
See the regex demo.
Usage note: if you use it with Java's .matches() method, the ^ and $ can be removed from the pattern. Remember to double escape backslashes in the string literal.
Details
^- start of string(?!\s)- no whitespace is allowed immediately to the right (at the start of the string)(?!.*\s[*?])- no whitespace is allowed after any 0+ chars, as many as possible, before*or?(?!.*[*?]\s)- no whitespace is allowed after any 0+ chars, as many as possible, after*or?(?:[?\s]*[a-zA-Z0-9]){2}- two sequences of[?\s]*- 0 or more?or/and whitespaces[a-zA-Z0-9]- an alphanumeric char
[a-zA-Z0-9?\s]*- 0 or more letters, digits,?or whitespaces\*?- an optional?char$- end of the string.