Java Regex with "Joker" characters

Question

I try to have a regex validating an input field. What i call "joker" chars are '?' and '*'. Here is my java regex :

"^$|[^\\*\\s]{2,}|[^\\*\\s]{2,}[\\*\\?]|[^\\*\\s]{2,}[\\?]{1,}[^\\s\\*]*[\\*]{0,1}"

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 at all

So for example :

• abcd = OK
• ?bcd = OK
• ab?? = OK
• ab*= OK
• ab?* = OK
• ??cd = OK
• *ab = NOT OK
• ??? = NOT OK
• ab cd = NOT OK
• abcd = Not OK (space at the begining)

I've made the regex a bit complicated and I'm lost can you help me?

Answer 1

^(?:\?*[a-zA-Z\d]\?*){2,}\*?$

Explanation:

The regex asserts that this pattern must appear twice or more:

\?*[a-zA-Z\d]\?*

which asserts that there must be one character in the class [a-zA-Z\d] with 0 to infinity questions marks on the left or right of it.

Then, the regex matches \*?, which means an 0 or 1 asterisk character, at the end of the string.

Demo

Here is an alternative regex that is faster, as revo suggested in the comments:

^(?:\?*[a-zA-Z\d]){2}[a-zA-Z\d?]*\*?$

Demo