Use a DecimalFormatter:
double number = 0.9999999999999;
DecimalFormat numberFormat = new DecimalFormat("#.00");
System.out.println(numberFormat.format(number));
Will give you “0.99”. You can add or subtract 0 on the right side to get more or less decimals.
Or use ‘#’ on the right to make the additional digits optional, as in with #.## (0.30) would drop the trailing 0 to become (0.3).