余存储在数据库中的一些数据，并予读与游标那些数据。所有的数据是56.45，3.04，0.03的类型，所以小数点后两个数字。现在，我想总结他们，但它似乎不容易......我得到这些数字与 c.getDouble（3）然后我把它添加到喜欢的总和变量

I store some data in a database and I read those data with a cursor. All the data are 56.45 , 3.04, 0.03 type, so two numbers after the decimal point. Now I would like to sum them but it doesnt seem to be easy... I get those number with c.getDouble(3) then I add it to the sum variable like:

sum+= c.getDouble(4) * multi

多为1到100之间的整数，现在我的问题是，得到的总和变量后，我得到了一些像：59.51999999999999999。我不发表code，但有除外将String.valueOf 制作的数量出现在我的窗口小部件没有任何转换。所以任何经验？正如我算它应该是59.52，而是我得到这个数字与99999 ......这是为什么发生？ （有趣的事情，与一个 Math.round（）不工作，我得到59.0即使我设定（和）*百分之百.. 在此先感谢！

multi is an integer between 1 and 100. Now my problem is that, after getting the sum variable I get a number like: 59.51999999999999999. I do not post a code, but there is no conversion except a string.valueOf for making the number appear on my widget. So anybody experienced this? As I count it should be 59.52, but instead I get that number with 99999... Why is that happening? (funny thing that with a Math.round() does not work, I get 59.0 even if I set (sum)*100 / 100.. Thanks in advance!

推荐答案

其他的方法，你可以定义你的总和变量双，然后你可以设置的NumberFormat 为您的总和变量。

Other approach, you can define your sum variable as double and then you can set NumberFormat for your sum variable.

示例：

double sum = 21.2015;
NumberFormat formatter = new DecimalFormat("#.##");
formatter.format(sum);