正则表达式，用“。*”向后/向前看

Question

This word has to be taken with the space behind it
word like this has to be taken too
If the word is like \\gloss{word}, \\(anything here)sezione{word}, \\gloss{anything word anything), \\(anything here)sezione{anything word anything}, it must not be taken.
If the word inside is like \\(anything but gloss or sezione){ word } and \\{anything but gloss or sezione){strings word strings} it has to be taken.
Obviously aword, worda and aworda has not to be taken.

( the bold word has been taken, word has not)

I have problems in not catching the word that is inside "{.... word .....}"

My guess was (?<!(sezione\\{)|(gloss\\{))(\\b)( ?)word(\\b)(?!.*\\{}) so far, and I would have added a ".*" on the lookbehind and lookahead ( (?<!(sezione\\{)|(gloss\\{).*)[...] ) but like this it stops working.

If this matter, I plan to use Java's regex engine

Thanks in advance

edit: the major problem is

\\(anything here)sezione{anything word anything}

If I can NOT get this one, this should solve the whole problem

Answer 1

Let's set few hard facts about your use-case:

1. Java (and most of) regex engines don't support variable length lookbehind
2. Java regex engine doesn't support \\K pattern that allows you to reset the search

In absence of that you will need to use a workaround which works in 3 steps:

1. Make sure input is matching expected lookbehind pattern
2. If it does then remove matched String by lookbehind pattern
3. In the replaced String match and extract your search pattern

Consider following code:

String str = "(anything here)sezione{anything word anything}";
// look behind pattern
String lookbehind = "^.*?(?:sezione|gloss|word)\\{";
// make sure input is matching lookbehind pattern first
if (str.matches(lookbehind + ".*$")) {
        // actual search pattern
    Pattern p = Pattern.compile("[^}]*?\\b(word)\\b");
        // search in replaced String
    Matcher m = p.matcher(str.replaceFirst(lookbehind, ""));
    if (m.find())
        System.out.println(m.group(1));
        //> word
}

PS: You may need to improve code by checking for indexes in the input String for the starting point of search pattern.