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javaregexcapturing-group

Java regex: extract function names

I'm trying to extract a list of function names from a formula, but my regex is not working.

Given ( aaa(111) + bbb(222) ) / ccc ( 333 ) I need to obtain an array of strings containing aaa, bbb and ccc. Instead, I'm getting aaa(, bbb( and ccc (. how to make this work?

This is my attempt:

    String formula = "( aaa(111) + bbb(222) ) / ccc ( 333 )";
    Pattern pattern = Pattern.compile("((\\w+)\\s*\\()");
    Matcher matcher = pattern.matcher(formula);

    while(matcher.find()){
        System.out.println(matcher.group(1));
    }
Solution

  • You've got nested capture groups, make the first one a non-capture group:

    Pattern pattern = Pattern.compile("(?:(\\w+)\\s*\\()");

    or as pointed out by Didier L just remove the outer group:

    Pattern pattern = Pattern.compile("((\\w+)\\s*\\(");