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

if you have your own speical rounding rule, you have to implement on your own... — Kent, Mar 24 '14 at 12:27
You seem to be testing "10.12445" in your second set of tests - didn't you want "10.12556"? — OldCurmudgeon, Mar 24 '14 at 12:43
sorry for the typo,Thanks for reply just corrected. its 10.12556 only — sunleo, Mar 24 '14 at 12:45
@sunleo `10.12556` with `BigDecimal.ROUND_HALF_EVEN` gives `10.13`, and not `10.12`, and I think that this is what you want... — Florent Bayle, Mar 24 '14 at 12:49
Yes That's correct.Thanks for enlighten me.Pls maks as Answer. — sunleo, Mar 24 '14 at 13:01
Your question shows incorrect output: the last three lines of your second example give "10.13" when you print it. How do you print it? like this: `System.out.println(b.setScale(2, BigDecimal.ROUND_HALF_DOWN));`? Maybe.. - do you realize that BigDecimal is immutable and that `setScale` returns a new BigDecimal, that it doesn't change the existing one? — Erwin Bolwidt, Mar 24 '14 at 13:35
Downvoted question as output shown does not match the code shown (where are the `println` statements?). And the output for `RoundingMode.HALF_UP` and for `RoundingMode.HALF_EVEN` in the second block is not what Java would return. — Frans, Jan 07 '19 at 11:39

score 106 · Accepted Answer · edited Apr 20 '20 at 14:26

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)

I prefer to setScale after the new BigDecimal in the same line, but this answer helps me. new BigDecimal("10.12345").setScale(2, BigDecimal.ROUND_HALF_EVEN) — bpedroso, Oct 10 '17 at 16:38
`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)` — Sophia Price, Apr 20 '20 at 13:16

Erwin Bolwidt · Answer 2 · 2014-03-24T13:05:54.143

16

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);
}

edited Mar 24 '14 at 13:05

answered Mar 24 '14 at 12:30

Erwin Bolwidt

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a.add(new BigDecimal("0.001")).setScale(2, RoundingMode.HALF_UP) tried this is not working ? – sunleo Mar 24 '14 at 12:41
Not sure where the problem is for you. Try the code example I added, it prints "10.13". BTW you changed the question after I gave the answer, you originally asked to round "10.12345" to "10.12" and "10.12445" to "10.13". – Erwin Bolwidt Mar 24 '14 at 13:06
Your problem is probably the same as why you are printing the wrong output in your question itself (`new BigDecimal("10.12556").setScale(2, BigDecimal.ROUND_HALF_UP)` is `10.13`, not `10.12`) as your printed. As I said above, the only thing I can think of is that you assume that `setScale` changes the BigDecimal - but it does not, as they are immutable - the method returns a new BigDecimal. – Erwin Bolwidt Mar 24 '14 at 14:06

score 2 · Answer 3 · answered Mar 24 '14 at 12:28

You may try this:

public static void main(String[] args) {
    BigDecimal a = new BigDecimal("10.12345");
    System.out.println(toPrecision(a, 2));
}

private static BigDecimal toPrecision(BigDecimal dec, int precision) {
    String plain = dec.movePointRight(precision).toPlainString();
    return new BigDecimal(plain.substring(0, plain.indexOf("."))).movePointLeft(precision);
}

OUTPUT:

10.12

score 2 · Answer 4 · answered Mar 24 '14 at 12:45

You can call setScale(newScale, roundingMode) method three times with changing the newScale value from 4 to 3 to 2 like

First case

    BigDecimal a = new BigDecimal("10.12345");

    a = a.setScale(4, BigDecimal.ROUND_HALF_UP); 
    System.out.println("" + a); //10.1235
    a = a.setScale(3, BigDecimal.ROUND_HALF_UP); 
    System.out.println("" + a); //10.124
    a = a.setScale(2, BigDecimal.ROUND_HALF_UP);
    System.out.println("" + a); //10.12

Second case

    BigDecimal a = new BigDecimal("10.12556");

    a = a.setScale(4, BigDecimal.ROUND_HALF_UP); 
    System.out.println("" + a); //10.1256
    a = a.setScale(3, BigDecimal.ROUND_HALF_UP); 
    System.out.println("" + a); //10.126
    a = a.setScale(2, BigDecimal.ROUND_HALF_UP);
    System.out.println("" + a); //10.13

score 1 · Answer 5 · answered Nov 14 '22 at 16:45

According to the docs, setScale(int, int), has not been recommended since Java 1.5, when enums were first introduced:

The new setScale(int, RoundingMode) method should be used in preference to this legacy method.

It was finally deprecated in Java 9.

You should call setScale(2, RoundingMode.HALF_EVEN) instead. It makes error checking much simpler, since you can't pass in an undefined enum, but you can certainly pass in an integer mode which is undefined.

Rounding Bigdecimal values with 2 Decimal Places

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