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

Answer 1

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.

Answer 2

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: (?<!a)b, which is b not preceeded by a

Answer 3

You could capture the (2001) part and replace the rest with nothing.

public static string extractYearString(string input) {
    return input.replaceAll(".*\(([0-9]{4})\).*", "$1");
}

var subject = "(2001) (asdf) (dasd1123_asd 21.01.2011 zqge)(dzqge) name (20019)";
var result = extractYearString(subject);
System.out.println(result); // <-- "2001"

.*\(([0-9]{4})\).* 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)