解决double类型计算时丢失精度问题

问题：double类型在进行计算时可能会丢失精度

double v1 = 0.2;
double v2 = 0.3;
double v3 = v2 - v1;

预期：v3=0.1

实际：v3=0.09999999999999998

解决：用BigDecimal类型包装一下数据然后计算(需要先把数据转为String类型！)

不转为String类型：

double v1 = 0.2;
double v2 = 0.3;
double v3 = v2 - v1;
BigDecimal b1 = new BigDecimal(v1);
BigDecimal b2 = new BigDecimal(v2);
double b3 = b2.subtract(b1).doubleValue();

b3=0.09999999999999998

正确方式：

double v1 = 0.2;
double v2 = 0.3;
double v3 = v2 - v1;
BigDecimal s1 = new BigDecimal(String.valueOf(v1));
BigDecimal s2 = new BigDecimal(String.valueOf(v2));
double s3 = s2.subtract(s1).doubleValue();

代码示例：

    public static void main(String[] args) {
        double v1 = 0.2;
        double v2 = 0.3;
        double v3 = v2 - v1;
        System.out.println("v3:" + v3);
        System.out.println("-------------");
        BigDecimal b1 = new BigDecimal(v1);
        BigDecimal b2 = new BigDecimal(v2);
        double b3 = b2.subtract(b1).doubleValue();
        System.out.println("b3:" + b3);
        System.out.println("-------------");
        BigDecimal s1 = new BigDecimal(String.valueOf(v1));
        BigDecimal s2 = new BigDecimal(String.valueOf(v2));
        double s3 = s2.subtract(s1).doubleValue();
        System.out.println("s3:" + s3);
    }

v3:0.09999999999999998
-------------
b3:0.09999999999999998
-------------
s3:0.1