public static String getNumberStr(Double num) {
if (num == null) {
return "";
}
final DecimalFormat n = new DecimalFormat("#.####################");
n.setDecimalFormatSymbols(new DecimalFormatSymbols(new Locale("EN")));
return n.format(num);
}
BigDecimal one = new BigDecimal(99999999998l);
BigDecimal two = new BigDecimal(1);
one = one.add(two); // сложение
System.out.println(one.round(new MathContext(3,RoundingMode.HALF_UP)));