public static Formatter forNumbers(@Nonnull String format) {
        return new NumberFormat(format);
    }
@Test
    public void testDigitsAndGrouping() {
        Formatter f = forNumbers("00");
        check(-5, f, "-05");

        f = forNumbers(".00");
        check(-0.5, f, "-.50");

        f = forNumbers("0,909.090");
        check(-123.4, f, "-0,123.400");

        f = forNumbers("9,090.909");
        check(-123.4, f, "  -123.40 ");

        f = forNumbers("9G99G999D99");
        check(-123456.78, f, "-1,23,456.78");
    }