Java: splitting a comma-separated string but ignoring commas in quotes

Question

I have a string vaguely like this:

foo,bar,c;qual=\"baz,blurb\",d;junk=\"quux,syzygy\"

that I want to split by commas -- but I need to igno

Answer 1

While I do like regular expressions in general, for this kind of state-dependent tokenization I believe a simple parser (which in this case is much simpler than that word might make it sound) is probably a cleaner solution, in particular with regards to maintainability, e.g.:

String input = "foo,bar,c;qual=\"baz,blurb\",d;junk=\"quux,syzygy\"";
List result = new ArrayList();
int start = 0;
boolean inQuotes = false;
for (int current = 0; current < input.length(); current++) {
    if (input.charAt(current) == '\"') inQuotes = !inQuotes; // toggle state
    else if (input.charAt(current) == ',' && !inQuotes) {
        result.add(input.substring(start, current));
        start = current + 1;
    }
}
result.add(input.substring(start));

If you don't care about preserving the commas inside the quotes you could simplify this approach (no handling of start index, no last character special case) by replacing your commas in quotes by something else and then split at commas:

String input = "foo,bar,c;qual=\"baz,blurb\",d;junk=\"quux,syzygy\"";
StringBuilder builder = new StringBuilder(input);
boolean inQuotes = false;
for (int currentIndex = 0; currentIndex < builder.length(); currentIndex++) {
    char currentChar = builder.charAt(currentIndex);
    if (currentChar == '\"') inQuotes = !inQuotes; // toggle state
    if (currentChar == ',' && inQuotes) {
        builder.setCharAt(currentIndex, ';'); // or '♡', and replace later
    }
}
List result = Arrays.asList(builder.toString().split(","));