Unexpected BigDecimal result. 1 divided by 3 results in 1. Unsure why

Question

Possible Duplicate:
Addition for BigDecimal

I feel like I'm missing something obvious, but cannot figure out what it is. I'm trying to use BigDecimal to get the decimal portion of a division between two numbers. A very simple case, 1.00 divided by 3.00 should be 0.(3) repeating. However, I keep getting a result of 1.00.

BigDecimal num = new BigDecimal(1.00).setScale(2);
BigDecimal divisor = new BigDecimal(3.00).setScale(2);

num.divide(divisor, BigDecimal.ROUND_HALF_UP);

System.out.print(num);

My result is 1.00 and I can't figure out why?

score 14 · Accepted Answer · answered Jan 07 '13 at 18:59

14

The result of num.divide is ignored. You need to set that back into a variable

    BigDecimal num = new BigDecimal(1.00).setScale(2);
    BigDecimal divisor = new BigDecimal(3.00).setScale(2);

    BigDecimal result = num.divide(divisor, BigDecimal.ROUND_HALF_UP);

    System.out.print(result);

This prints 0.33

answered Jan 07 '13 at 18:59

Daniel Kaplan

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+1 You have to do this as BigDecimal (and BigInteger which it uses) is immutable. – Peter Lawrey Jan 07 '13 at 19:04
Ah, thank you. I totally missed that despite it being the very first word in the documentation. – Joshua Weise Jan 07 '13 at 19:46

score 3 · Answer 2 · answered Jan 07 '13 at 19:00

3

BigDecimals are immutable. You need to assign the result to the variable.

answered Jan 07 '13 at 19:00

Honza Brabec

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score 2 · Answer 3 · answered Jan 07 '13 at 19:00

2

num.divide doesn't change num it returns the result.

Try:

num = num.divide(divisor, BigDecimal.ROUND_HALF_UP)

answered Jan 07 '13 at 19:00

Peter Svensson

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Unexpected BigDecimal result. 1 divided by 3 results in 1. Unsure why

3 Answers3