Rounding necessary with BigDecimal numbers

java rounding bigdecimal
Mehdi picture Mehdi · May 24, 2012 · Viewed 71.1k times · Source

I want to set scale of two BigDecimal numbers a and b . as in this example :

BigDecimal a = new BigDecimal("2.6E-1095");
        BigDecimal b = new BigDecimal("2.7E-1105");
        int i = 112, j=1;

        BigDecimal aa = a.setScale(i+j);
        BigDecimal bb = b.setScale(i+j);

and when i run i have this exception:

java.lang.ArithmeticException: Rounding necessary
    at java.math.BigDecimal.divideAndRound(BigDecimal.java:1439)
    at java.math.BigDecimal.setScale(BigDecimal.java:2394)
    at java.math.BigDecimal.setScale(BigDecimal.java:2437)

Why rounding is necessary ? if i don't want to make around, what is solution please ?

Thanks

Answer

brain picture brain · May 24, 2012

You have two BigDecimal numbers both of which require over a 1000 decimal places. Trying to set the scale to only have 113 decimal places means you will lose precision and therefore you need to round.

You can use the setScale methods that take a RoundingMode to prevent the exception but not the rounding.

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