为什么我的android应用程序中的计算结果错误？

Question

In my app i am using this to calculate a number:

double result = ((a * a) + (b * b) - (2 * a * b));

If a for example a = 2 and b = 3.9, then the result should be 3.61. However, when I display "result" i get the number 3.610000000000001.

What is wrong here? How can I correct this error?

Answer 1

You can format your output value by using the following construct:

String result;
twoDForm = new DecimalFormat("#0.00");
result = twoDForm.format(value);

After this, in result you will have your value in X.XX format