How do I express “:” but not preceded by “\” in a Java regular expression?

Question

How can I express \"not preceded by\" in a Java regular expression? For example I would like to search for \":\" but only when it is not directly preceded by \"\\\". How c

Answer 1

Did you try using a character class with the complement operator?

    String s1 = "foo : bar";
    String s2 = "foo \\: bar";

    Pattern p  = Pattern.compile("[^\\\\]:");

    Matcher m = p.matcher(s1);
    if(m.find()) {
        System.out.println(m.group());
    }

    m = p.matcher(s2);
    if(m.find()) {
        System.out.println(m.group());
    }