简书链接:BigDecimal的问题
文章字数：432,阅读全文大约需要1分钟

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100.386->ROUND_HALF_EVEN 100.39
100.386->ROUND_HALF_UP 100.39
100.386->ROUND_HALF_DOWN 100.39
100.386->ROUND_UP 100.39
100.386->ROUND_DOWN 100.38
100.386->ROUND_FLOOR 100.38
100.386->ROUND_CEILING 100.39
------------
100.382->ROUND_HALF_EVEN 100.38
100.382->ROUND_HALF_UP 100.38
100.382->ROUND_HALF_DOWN 100.38
100.382->ROUND_UP 100.39
100.382->ROUND_DOWN 100.38
100.382->ROUND_FLOOR 100.38
100.382->ROUND_CEILING 100.39
------------
100.38->ROUND_HALF_EVEN 100.38
100.38->ROUND_HALF_UP 100.38
100.38->ROUND_HALF_DOWN 100.38
100.38->ROUND_UP 100.38
100.38->ROUND_DOWN 100.37
100.38->ROUND_FLOOR 100.37
100.38->ROUND_CEILING 100.38
------------
100.38->ROUND_HALF_EVEN 100.38
100.38->ROUND_HALF_UP 100.38
100.38->ROUND_HALF_DOWN 100.38
100.38->ROUND_UP 100.38
100.38->ROUND_DOWN 100.37
100.38->ROUND_FLOOR 100.37
100.38->ROUND_CEILING 100.38
------------

   BigDecimal bg = new BigDecimal(money);
//        double f1 = bg.setScale(2, BigDecimal.ROUND_FLOOR).doubleValue();//抹掉后面的。
//        return f1;

  String format = String.format("money %.2f", 100.356f);//100.36
        DecimalFormat df = new DecimalFormat("#.00");
        System.out.println("test:" + df.format(100.356f));
        System.out.println(format);


        NumberFormat nf = NumberFormat.getNumberInstance();
        nf.setMaximumFractionDigits(2);
        double f = 100.356f;
        System.out.println(nf.format(f));




// 经过测试系统的api,无论哪种只保留2位小数，第三位没有或者存在 都会导致出现不同的结果， 需求是不受后面有没有或者存在的影响，所以写了这个东西。

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    public  static String keepFormatNoney(Object money, int keepCount) {
        String moneyStr = money + "";
        int index = moneyStr.indexOf(".");
        if (index == -1) {
            return moneyStr;
        } else {
            int end;
            if ((index + keepCount + 1) > moneyStr.length()) {
                end = moneyStr.length();//index+2>s.length()?index+2:s.length()
            } else {
                end = index + keepCount + 1;

            }
            String substring = moneyStr.substring(0, end);
            return substring;
        }
    }

        System.out.println("final str " + keepFormatNoney(10.333,2));
        System.out.println("final str " + keepFormatNoney(10.32345,2));
        System.out.println("final str " + keepFormatNoney(103.3,3));
        System.out.println("final str " + keepFormatNoney(103.3333,3));

final str 100.12
final str 10.33
final str 10.32
final str 103.3
final str 103.333

小数点 乘上100保留3位数的办法

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public static String formatMoney(float money) {
       int mymoney = (int) (money * 100);
       String format = String.format("%3d", mymoney);
       return format.replace(" ", "0");
       /*if(money<10){
           return  "00"+money;
       }else{
           return money+"";
       }*/
   }

然而还是有问题
修正后

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public static String formatMoney(double money) {
    BigDecimal bigDecimal = new BigDecimal(Double.toString(money));
    int mymoney = bigDecimal.multiply(new BigDecimal(Double.toString(100))).intValue();
  /*  bigDecimal = new BigDecimal(Double.toString(mymoney));
    bigDecimal.setScale(2, BigDecimal.ROUND_DOWN);
    double reverseValue = bigDecimal.divide(new BigDecimal(Double.toString(100))).doubleValue();

    if (reverseValue != money) {
        throw new RuntimeException("rever error:" + moneyStr + ",doResult:" + reverseValue);
    }*/
    String format = String.format("%3d", mymoney);
    return format.replace(" ", "0");
}
public static String formatMoney(String moneyStr) {
    double money = Double.parseDouble(moneyStr);
    return formatMoney(money);
}