Android - 精确的数学计算 [英] Android - exact mathematical calculation

问题描述

我遇到了问题，我正在开发一个能够进行数学计算的应用程序。这些计算必须准确（或者说明显不是错误的）

I have got a Problem, I am developing an Application which should be able to do some mathematic calculations. These calculations have to be exact (or rather not obviously wrong)

但这个简单的代码

double a = 3.048d;
double b = 1000d;

double c = a / b;

给我一​​个错误的结果c不是预期的0.003048而是0.0030480000000000004这显然是错误的。

gives me a wrong result c is not 0.003048 as expected instead it is 0.0030480000000000004 which is obviously wrong.

double d = 3.048 / 1000; 

第二个代码snipet给出了正确的结果。

this second code-snipet gives the correct result.

我知道用计算机计算时所有的浮点运算都不准确，但我不知道如何解决这个问题。

I am aware that all floatingpoint arithmetic is not exact when calculating with computers but I don't know how to solve this problem.

提前感谢！

Ludwig

thanks in advance!
Ludwig

开发：

- Android 2.2

Testdevice：

- HTC Desire

Developing for:
- Android 2.2
Testdevice:
- HTC Desire

推荐答案

什么 BigDecimal <需要用于精确的精确度/ a>对象：

What you need to use for exact percision is the BigDecimal object:

BigDecimal a = new BigDecimal("3.048");
BigDecimal b = new BigDecimal(1000);

BigDecimal c = a.divide(b);

System.out.println(c); //0.003048

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