Java四舍五入到两位小数

Question

I have a number

double num = 1.234567;

and I'm trying to keep only two decimals

num = (int)((num * 100) + 0.5) / 100.0;

but the actual number I got is 1.230000000001. How can I get rid of the 0000000001 part?

Answer 1

Try DecimalFormat :

DecimalFormat twoDp= new DecimalFormat("#.##");
Double.valueOf(twoDp.format(num));

Answer 2

You can't, unless you switch to a decimal radix. Doubles and floats don't have decimal places, they have binary places, so you can't round or truncate them to specific numbers of decimal places except in the cases where the value representations are congruent, ie the negative powers of 2.

So you have to either use DecimalFormat if you are presenting the result, or BigDecimal if you want to keep computing with it.

Any solution that ends by turning the value back into floating point is incorrect.

Answer 3

String result = String.format("%.2f", num);

Answer 4

Try this .. this should solve it

       Double num = //value
   num = //arithmetic


   String temp =num.toString().split("\\.")[0];
       int precision=temp.length();
       BigDecimal b =new BigDecimal(num,new MathContext(precision+2));
   System.out.println(b.doubleValue());