Question

In my program I use a lot of Strings and StringBuilders. I would like to get rid of the StringBuilder toString() method and use CharSequences throughout. However I need access to the indexOf method (which is available in both StringBuilder and String but not in other implementations). How might I implement an interface that will make this function visible?

Answer 1

Well, you could do it reasonably easily by hardcoding tests for known types, and doing it “manually” otherwise:

public static int indexOf(CharSequence input, String needle) {
    if (input instanceof String) {
        String text = (String) input;
        return text.indexOf(needle);
    }
    if (input instanceof StringBuilder) {
        StringBuilder text = (StringBuilder) input;
        return text.indexOf(needle);
    }
    // TODO: Do this without calling toString() :)
    return input.toString().indexOf(needle);
}

This is pretty ugly in terms of hard-coding the types, but it’ll work.