How to round a number to n decimal places in Java
- by Alex Spurling
What I'd like is a method to convert a double to a string which rounds using the half-up method. I.e. if the decimal to be rounded is a 5, it always rounds up the previous number. This is the standard method of rounding most people expect in most situations.
I also would like only significant digits to be displayed. That is there should not be any trailing zeroes.
I know one method of doing this is to use the String.format method:
String.format("%.5g%n", 0.912385);
returns:
0.91239
which is great, however it always displays numbers with 5 decimal places even if they are not significant:
String.format("%.5g%n", 0.912300);
returns:
0.91230
Another method is to use the DecimalFormatter:
DecimalFormat df = new DecimalFormat("#.#####");
df.format(0.912385);
returns:
0.91238
However as you can see this uses half-even rounding. That is it will round down if the previous digit is even. What I'd like is this:
0.912385 -> 0.91239
0.912300 -> 0.9123
What is the best way to achieve this in Java?
