Keep decimal places

Here I use two methods, the first is to use BigDecimal, and the second is to use DecimalFormat.

The first method:
Usage: pass in the double value and return a String type

 public static String keep_two_decimals(double number){
        BigDecimal bigDecimal   =   new   BigDecimal(number);
        double  s  =   bigDecimal.setScale(2).doubleValue();
        return String.valueOf(s);
    }

Among them, you can set it by yourself according to the requirements, and the default method is rounding

 setScale(2);//It means that 2 decimal places are reserved, and the default rounding method is used 

 setScale(2,BigDecimal.ROUND_DOWN);//Directly delete the extra decimal places 11.116 = 11.11

 setScale(2,BigDecimal.ROUND_UP);//If the adjacent bit is not zero, carry directly; if the adjacent bit is zero, carry not. 11.114 = 11.12

 setScale(2,BigDecimal.ROUND_HALF_UP);//Round to 2.335 = 2.33, 2.3351 = 2.34

 setScaler(2,BigDecimal.ROUND_HALF_DOWN);//Rounding: 2.335 ~ 2.33, 2.3351 ~ 2.34, 11.117 ~ 11.12

The second method:

 public static String keepTwoByDecimalFormat(double number) {
        DecimalFormat df = new java.text.DecimalFormat("#.00");
        String s = df.format(number);//Default String.format will automatically round
        return s;
    }

Here, we also learn the rules used by predecessors to judge by removing the redundant 0 of double string

 public static String doubleTypeRep(String str) {
        if (!str.contains(".")) {
            return str;
        }
        String[] strArr = str.split("\\.");
        String end = strArr[1];
        if (end.matches("[0]{2}")) {
            return strArr[0];
        } else if (end.matches("[0-9][0]")) {
            return str.substring(0, str.length() - 1);
        } else if (end.matches("[0]")) {
            return strArr[0];
        }

        return str;

    }

use:

 public static String keepTwoByDecimalFormat(double number) {
        DecimalFormat df = new java.text.DecimalFormat("#.00");
        String s = df.format(number);//Default String.format will automatically round
        return doubleTypeRep(s);
    }

In this way, if there is a number like 234.00234.10, it will return 234234.1 when it returns

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