private function _printTargets($names, $descriptions, $heading, $maxlen)
    {
        $spaces = '  ';
        while (strlen($spaces) < $maxlen) {
            $spaces .= $spaces;
        }
        $msg = "";
        $msg .= $heading . PHP_EOL;
        $msg .= str_repeat("-", 79) . PHP_EOL;

        $total = count($names);
        for ($i = 0; $i < $total; $i++) {
            $msg .= " ";
            $msg .= $names[$i];
            if (!empty($descriptions)) {
                $msg .= substr($spaces, 0, $maxlen - strlen($names[$i]) + 2);
                $msg .= $descriptions[$i];
            }
            $msg .= PHP_EOL;
        }
        if ($total > 0) {
            self::$out->write($msg . PHP_EOL);
        }
    }