RegExp matching string not starting with my

Question

For PMD I d like to have a rule which warns me of those ugly variables which start with my  This means I have to accept all variables which do NOT start with my  So  I need a RegEx  re  which behaves as follows  re match  myVar            false re match  manager          true re match  thisIsMyVar      true re match  myOtherVar       false re match  stuff            true  I ve tried different ones but haven t got it working yet

User · Accepted Answer

You could either use a lookahead assertion like others have suggested. Or, if you just want to use basic regular expression syntax:

^(.?$|[^m].+|m[^y].*)

This matches strings that are either zero or one characters long (^.?$) and thus can not be my. Or strings with two or more characters where when the first character is not an m any more characters may follow (^[^m].+); or if the first character is a m it must not be followed by a y (^m[^y]).

User · Answer

my  w     should work   It first ensures that it s not possible to match my at the start of the string  and then matches alphanumeric characters until the end of the string  Whitespace anywhere in the string will cause the regex to fail  Depending on your input you might want to either strip whitespace in the front and back of the string before passing it to the regex  or use add optional whitespace matchers to the regex like   s    my   w   s    In this case  backreference 1 will contain the name of the variable   And if you need to ensure that your variable name starts with a certain group of characters  say  A-Za-z    use       my  A-Za-z   w     Note the change from   to

User · Answer

Wouldn t it be significantly more readable to do a positive match and reject those strings - rather than match the negative to find strings to accept     my

User · Answer

my          expression  is a negative lookahead  it matches a position where expression doesn t match starting at that position

[regex] RegExp matching string not starting with my

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