JavaWeb - Util 之 BigDecimalUtil（解决浮点型商业运算中丢失精度的问题）

测试代码

package com.mmall.test;

import org.junit.Test;
import java.math.BigDecimal;

public class BigDecimalTest {

    @Test
    public void test1(){
        System.out.println(0.05+0.01);
        System.out.println(1.0-0.42);
        System.out.println(4.015*100);
        System.out.println(123.3/100);
    }

/*
0.060000000000000005
0.5800000000000001
401.49999999999994
1.2329999999999999
*/

    @Test
    public void test2(){
        BigDecimal b1 = new BigDecimal(0.05);
        BigDecimal b2 = new BigDecimal(0.01);
        System.out.println(b1.add(b2));
    }

/*
0.06000000000000000298372437868010820238851010799407958984375
*/

    @Test
    public void test3(){
        BigDecimal b1 = new BigDecimal("0.05");
        BigDecimal b2 = new BigDecimal("0.01");
        System.out.println(b1.add(b2));
    }

/*
0.6
*/

}

Ps：综上所述，得出结论，必须把计算的浮点数转成String类型进行构造BigDecimal函数才能精确计算。

工具类

package com.mmall.util;

import java.math.BigDecimal;

public class BigDecimalUtil {

    private BigDecimalUtil(){
    }

    public static BigDecimal add(double v1,double v2){
        BigDecimal b1 = new BigDecimal(Double.toString(v1));
        BigDecimal b2 = new BigDecimal(Double.toString(v2));
        return b1.add(b2);
    }

    public static BigDecimal sub(double v1,double v2){
        BigDecimal b1 = new BigDecimal(Double.toString(v1));
        BigDecimal b2 = new BigDecimal(Double.toString(v2));
        return b1.subtract(b2);
    }


    public static BigDecimal mul(double v1,double v2){
        BigDecimal b1 = new BigDecimal(Double.toString(v1));
        BigDecimal b2 = new BigDecimal(Double.toString(v2));
        return b1.multiply(b2);
    }

    public static BigDecimal div(double v1,double v2){
        BigDecimal b1 = new BigDecimal(Double.toString(v1));
        BigDecimal b2 = new BigDecimal(Double.toString(v2));
        return b1.divide(b2,2,BigDecimal.ROUND_HALF_UP);//四舍五入,保留2位小数
        //除不尽的情况
    }
}