class CaseTools {

    public static String camel(String s) {
        if (s == null) {
            return null;
        }
        final var result = new char[s.length()];
        int dst = 0;
        var capIt = true;
        for (int src = 0; src < s.length(); src++) {
            if (s.charAt(src) == '_') {
                capIt = true;
            } else {
                if (capIt) {
                    capIt = false;
                    result[dst++] = Character.toUpperCase(s.charAt(src));
                } else {
                    result[dst++] = Character.toLowerCase(s.charAt(src));
                }
            }
        }
        return new String(result, 0, dst);
    }

}