How to match a string (?,?,?) in Java

Question

My input string is of the form: String input = "(?,?,?)";

I am not able to come up with a valid regex to identify such strings

I have tried with following regex:

String regex = "(\\?,*)"; 

Assertion fails with the above regex for input strings such as (?,?) or (?,?,?,?)

Answer 1

You could match (? and then repeat 1+ times ,? and match ) .

If a single question mark is also valid, you could change the quantifier from + to *

\(\?(?:,\?)+\)

Explanation

• \\(\\? Match (?
• (?:,\\?)+ Non capturing group, repeat 1+ times ,?
• \\) Match )

In Java

final String regex = "\\\\(\\\\?(?:,\\\\?)+\\\\)";

Regex demo | Java demo

Answer 2

A general regex pattern would be:

\(\?(?:,\?)*\)

Sample script:

String input = "(?,?,?,?)";
if (input.matches("\\(\\?(?:,\\?)*\\)")) {
    System.out.println("MATCH");
}

Here is an explanation of the regex:

\(        match a literal opening parenthesis
\?        match a single ?
(?:,\?)*  then match ,? zero or more times
\)        then match closing )