"#.00"；"######0.00" 保留俩位小数

首先明确#与0的区别：

#：为0则补位为空

0：没有则补位为0

Symbol Location Localized? Meaning 0 Number Yes Digit # Number Yes Digit, zero shows as absent . Number Yes Decimal separator or monetary decimal separator - Number Yes Minus sign , Number Yes Grouping separator E Number Yes Separates mantissa and exponent in scientific notation. Need not be quoted in prefix or suffix. ; Subpattern boundary Yes Separates positive and negative subpatterns % Prefix or suffix Yes Multiply by 100 and show as percentage u2030 Prefix or suffix Yes Multiply by 1000 and show as per mille value ¤ (u00A4) Prefix or suffix No Currency sign, replaced by currency symbol. If doubled, replaced by international currency symbol. If present in a pattern, the monetary decimal separator is used instead of the decimal separator. Prefix or suffix No Used to quote special characters in a prefix or suffix, for example, "##" formats 123 to "#123". To create a single quote itself, use two in a row: "# oclock".

格式化测试：

// 数字格式化测试
    @Test
    public void numberFormat (){
         
  {
        BigDecimal figureOne = BigDecimal.valueOf(0.59354);
        String format1 = new DecimalFormat("#.0000000").format(figureOne);//
        log.info(format1);//结果：.5935400
        String format2 = new DecimalFormat("#.00").format(figureOne);//保留俩位小数
        log.info(format2);//结果：.59
        String format3 = new DecimalFormat("0.00").format(figureOne);//保留俩位小数
        log.info(format3);//结果：0.59
        BigDecimal figureTwo = BigDecimal.valueOf(5201314.59354);
        String format4 = new DecimalFormat("###,###0.00").format(figureTwo);//三位一逗，保留一位
        log.info(format4);//结果：520,1314.59
        String format5 = new DecimalFormat("00.000").format(figureTwo);//取两位整数和三位小数
        log.info(format5);//结果：5201314.594
        String format6 = new DecimalFormat("0").format(figureTwo);//取所有整数
        log.info(format6);//结果：5201315
        String format7 = new DecimalFormat("#").format(figureTwo);//取所有整数部分
        log.info(format7);//结果：5201315
        String format8 = new DecimalFormat("#.##%").format(figureTwo);//以百分比方式计数，并取两位小数
        log.info(format8);//结果：520131459.35%
        //科学计数法
        long c = 299792458;//光速：299792458m/s
        String format9 = new DecimalFormat("#.#####E0").format(c);//五位小数
        log.info(format9);//结果：2.99792E8
        String format10 = new DecimalFormat("00.####E0").format(c);//两位整数和四位小数
        log.info(format10);//结果：29.9792E7
        String format11 = new DecimalFormat(",###").format(c);三位一逗
        log.info(format11);//结果：299,792,458
        String format12 = new DecimalFormat("光速大小为：###m/s").format(c);//和文本拼接
        log.info(format12);//结果：光速大小为：299792458m/s
    }
    }