BigDecimal三位分节法

参考：https://www.cnblogs.com/XT-xutao/p/9882404.html

package com.woyujiezhen.test;

import java.math.BigDecimal;
import java.text.DecimalFormat;

public class BigDecimalTest {
private static String formatDecimalPoint(BigDecimal bigDecimal, int decimalPoint) {
        StringBuilder format = decimalPoint == 0 ? new StringBuilder("#,##0") : new StringBuilder("#,##0.");
        StringBuilder decimal = new StringBuilder();
        for (int i = 0; i < decimalPoint; i++) {
            decimal.append("0");
        }
        if (bigDecimal == null) {
            return decimalPoint == 0 ? "0" : "0." + decimal;
        }
        if (BigDecimal.ZERO.compareTo(bigDecimal) > 0) {
            format = new StringBuilder("-").append(format);
        }
        DecimalFormat decimalFormat = new DecimalFormat(format.append(decimal).toString());
        return decimalFormat.format(bigDecimal);
    }
    
    public static void main(String[] args) {
        Integer a = null;
//        BigDecimal bigDecimal1 = new BigDecimal(a);
        String[] strs = {"12", "211", "3333", "0", "0.123", "00.55", null, "6.666", "88888888888.235555", "-12", "-333333333.2366", "-0.00", "-0.12"};
        for (String str : strs) {
            BigDecimal testDecimal;
            if (str == null) {
                testDecimal = null;
            } else {
                testDecimal = new BigDecimal(str);
            }
            for (int i = 0; i < 4; i++) {
                System.out.print(formatDecimalPoint(testDecimal, i));
                System.out.print("  ");
            }
            System.out.println();
        }
    }
}