Regex not operator

Question

Is there an NOT operator in Regexes  Like in that string     2001   asdf   dasd1123 asd 21 01 2011 zqge  dzqge  name  20019    I want to delete all    0-9a-zA-z     -      but not the one where it is a year   2001    So what the regex should return must be   2001  name   NOTE  something like        d   4  0-9a-zA-z     -      does not work for me  the  20019  somehow also matches

User · Answer

You could capture the  2001  part and replace the rest with nothing  public static string extractYearString string input        return input replaceAll  quot       0-9  4       quot    quot  1 quot       var subject    quot  2001   asdf   dasd1123 asd 21 01 2011 zqge  dzqge  name  20019  quot   var result   extractYearString subject   System out println result       lt --  quot 2001 quot         0-9  4       means     match anything    match a   character   begin capture  0-9  4  any single digit four times   end capture    match a   character    anything  rest of string

User · Answer

Not quite  although generally you can usually use some workaround on one of the forms     abc   which is character by character not a or b or c   or negative lookahead  a   b   which is a not followed by b or negative lookbehind     lt  a b  which is b not preceeded by a

User · Answer

No  there s no direct not operator  At least not the way you hope for   You can use a zero-width negative lookahead  however        2001  0-9a-zA-z     -        The         part means  only match if the text following  hence  lookahead  this doesn t  hence  negative  match this  But it doesn t actually consume the characters it matches  hence  zero-width    There are actually 4 combinations of lookarounds with 2 axes    lookbehind   lookahead   specifies if the characters before or after the point are considered positive   negative   specifies if the characters must match or must not match

[java] Regex not operator

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