Rounding Bigdecimal values with 2 Decimal Places

Question

I want a function to convert Bigdecimal 10.12 for 10.12345 and 10.13 for 10.12556. But no function is satisfying both conversion in same time.Please help to achieve this.

Below is what I tried.
With value 10.12345:

BigDecimal a = new BigDecimal("10.12345");  a.setScale(2, BigDecimal.ROUND_UP) a.setScale(2, BigDecimal.ROUND_CEILING) a.setScale(2, BigDecimal.ROUND_DOWN) a.setScale(2, BigDecimal.ROUND_FLOOR) a.setScale(2, BigDecimal.ROUND_HALF_DOWN) a.setScale(2, BigDecimal.ROUND_HALF_EVEN) a.setScale(2, BigDecimal.ROUND_HALF_UP) 

Output :

10.12345::10.13 10.12345::10.13 10.12345::10.12 10.12345::10.12 10.12345::10.12 10.12345::10.12 10.12345::10.12 

With value 10.12556:

BigDecimal b = new BigDecimal("10.12556");  b.setScale(2, BigDecimal.ROUND_UP) b.setScale(2, BigDecimal.ROUND_CEILING) b.setScale(2, BigDecimal.ROUND_DOWN) b.setScale(2, BigDecimal.ROUND_FLOOR) b.setScale(2, BigDecimal.ROUND_HALF_DOWN) b.setScale(2, BigDecimal.ROUND_HALF_EVEN) b.setScale(2, BigDecimal.ROUND_HALF_UP) 

Output :

10.12556::10.13 10.12556::10.13 10.12556::10.12 10.12556::10.12 10.12556::10.12 10.12556::10.12 10.12556::10.12 

Answer 1

I think that the RoundingMode you are looking for is ROUND_HALF_EVEN. From the javadoc:

Rounding mode to round towards the "nearest neighbor" unless both neighbors are equidistant, in which case, round towards the even neighbor. Behaves as for ROUND_HALF_UP if the digit to the left of the discarded fraction is odd; behaves as for ROUND_HALF_DOWN if it's even. Note that this is the rounding mode that minimizes cumulative error when applied repeatedly over a sequence of calculations.

Here is a quick test case:

BigDecimal a = new BigDecimal("10.12345"); BigDecimal b = new BigDecimal("10.12556");  a = a.setScale(2, BigDecimal.ROUND_HALF_EVEN); b = b.setScale(2, BigDecimal.ROUND_HALF_EVEN);  System.out.println(a); System.out.println(b); 

Correctly prints:

10.12 10.13 

UPDATE:

setScale(int, int) has not been recommended since Java 1.5, when enums were first introduced, and was finally deprecated in Java 9. You should now use setScale(int, RoundingMode) e.g:

setScale(2, RoundingMode.HALF_EVEN)

Answer 2

Add 0.001 first to the number and then call setScale(2, RoundingMode.ROUND_HALF_UP)

Code example:

public static void main(String[] args) {     BigDecimal a = new BigDecimal("10.12445").add(new BigDecimal("0.001"));     BigDecimal b = a.setScale(2, BigDecimal.ROUND_HALF_UP);     System.out.println(b); }