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
标签：BigDecimal,double,v1,v2,v3,丢失,new,精度 From： https://www.cnblogs.com/Bernard94/p/18458872