java中小数的加减乘除

单价 * 数量 * 折扣=应收金额 或者正常的加减，会突然出现很多个小数

public static void main(String[] args) {
        double kk = 3.14;
        kk += 0.37;
        float ff = 3.14f;
        ff += 0.37f;
        System.out.println("double kk =" + kk);
        System.out.println("float ff =" + ff);
    }

输出结果：
double kk =3.5100000000000002 float ff =3.5100002

小数加减乘除建议用BigDecimal；

public static void main(String[] args) {
        //小数加减乘除用BigDecimal
        BigDecimal b1 = new BigDecimal("3.14");
        BigDecimal b2 = new BigDecimal("0.37");
        BigDecimal b3 = b1.add(b2);//
        BigDecimal b4 = b1.subtract(b2);//
        BigDecimal b5 = b1.multiply(b2);
        System.out.println("3.14 + 0.37 = " + b3);
        System.out.println("3.14 - 0.37 = " + b4);
        System.out.println("3.14 * 0.37 = " + b5);
    }
输出：
3.14 + 0.37 = 3.51
3.14 - 0.37 = 2.77
3.14 * 0.37 = 1.1618

JDK中BigDecimal类方法说明：https://www.yiibai.com/java/math/java_math_bigdecimal.html