Java - better performance String formatter

/**
     * Substitutes each {@code %s} in {@code template} with an argument. These
     * are matched by position - the first {@code %s} gets {@code args[0]}, etc.
     * If there are more arguments than placeholders, the unmatched arguments will
     * be appended to the end of the formatted message in square braces.
     *
     * @param template a non-null string containing 0 or more {@code %s}
     *     placeholders.
     * @param args the arguments to be substituted into the message
     *     template. Arguments are converted to strings using
     *     {@link String#valueOf(Object)}. Arguments can be null.
     */
    public static String format(String template, Object... args) {
        template = String.valueOf(template); // null -> "null"
        // start substituting the arguments into the '%s' placeholders
        StringBuilder builder = new StringBuilder(template.length() + 16 * args.length);
        int templateStart = 0;
        int i = 0;
        while (i < args.length) {
            int placeholderStart = template.indexOf("%s", templateStart);
            if (placeholderStart == -1) {
                break;
            }
            builder.append(template.substring(templateStart, placeholderStart));
            builder.append(args[i++]);
            templateStart = placeholderStart + 2;
        }
        builder.append(template.substring(templateStart));

        // if we run out of placeholders, append the extra args in square braces
        if (i < args.length) {
            builder.append(" [");
            builder.append(args[i++]);
            while (i < args.length) {
                builder.append(", ");
                builder.append(args[i++]);
            }
            builder.append(']');
        }

        return builder.toString();
    }

   public static void main(String[] args) {
        Stopwatch stopwatch = new Stopwatch();
        stopwatch.start();
        String result = Formatter.format("My name is: %s. I was start from: %s. ", "Sean", "25/05/2012", "another value here");
        stopwatch.stop();
        System.out.println(stopwatch.elapsedTime(TimeUnit.NANOSECONDS));
        System.out.println(result);
        stopwatch.reset();
        stopwatch.start();
        result = String.format("My name is: %s. I was start from: %s.", "Sean", "25/05/2012", "another value here");
        stopwatch.stop();
        System.out.println(stopwatch.elapsedTime(TimeUnit.NANOSECONDS));
        System.out.println(result);
    }