Sub-patterns can be wrapped by parentheses to build a group. This enables to restrict alternations, back reference the group or apply quantifier to the sub-pattern.
If this group should not be part of the match result or if no reference to this group is required, a non-capturing group can be created by adding
?:
behind the opening parenthesis.
However, if this non-capturing group does not have a quantifier, or does not wrap an alternation, then imaging this group is redundant.
"(?:number)\\d{2}"
"number\\d{2}" // it is anyway required "(?:number)?\\d{2}" // it is in fact optional
This rule does not report an issue if the non-capturing group is an alternation.
"(?:number|string)"