Question

I would like to format some double values to a specific number of digits ignoring starting zeros.

Example, lets say format to 6 digits:

131.468627436358  ->  131.469
3.16227766016838  ->  3.16228
0.66018099039325  ->  0.660181
0.02236067977499  ->  0.0223607

Answer 1

BigDecimal allows handling of significant figures correctly. This:

MathContext round3SigFig = new MathContext(3,RoundingMode.HALF_UP);
System.out.println((new BigDecimal(0.000923874932)).round(round3SigFig));

produces:

0.000924

Obviously, though, passing your floating points through an arbitrary precision object representation isn’t ideal.