What causes "Non-terminating decimal expansion" exception from BigDecimal.divide? [duplicate]

Question

I've used BigDecimals before but not very often and I was working on something this morning and I kept getting the following exception:

Exception in thread "main" java.lang.ArithmeticException: Non-terminating decimal expansion; no exact representable decimal result.     at java.math.BigDecimal.divide(BigDecimal.java:1594) 

I was attempting to set the scale and use rounding to eliminate the problem like so:

    BigDecimal bd1 = new BigDecimal(1131).setScale(2,BigDecimal.ROUND_HALF_UP);     BigDecimal bd2 = new BigDecimal(365).setScale(2,BigDecimal.ROUND_HALF_UP);     BigDecimal bd3 = bd1.divide(bd2).setScale(2,BigDecimal.ROUND_HALF_UP);     System.out.println("result: " + bd3); 

However, I keep getting the same exception. Anyone able to show me where I have made a mistake?

Answer 1

Non-terminating decimal need rounding

When using divide you should use a MathContext with RoundingMode in case the exact result has an infinite number of decimals.

Such is your case:

MathContext mc = new MathContext(2, RoundingMode.HALF_UP) ; BigDecimal bd3 = bd1.divide(bd2, mc); 

Alternatively call divide passing the scale and rounding mode.

BigDecimal bd3 = bd1.divide(bd2, RoundingMode.HALF_UP); 

Answer 2

Here's the problem

bd1.divide(bd2) 

You need to use one of the overloaded divide() methods that takes a rounding mode (in various forms) - you cannot do the rounding after the division because with a nonterminating fraction the intermediate result would either already need to be rounded, or require infinite storage space.