Throwing Exception RoundingMode.UNNECESSARY
I wrote this to test it BigDecimal
in action, but found myself throwing an RoundingMode.UNNECESSARY
exception. Can someone explain why?
public class TestRounding2 {
public static void main(String args[]) {
Locale swedish = new Locale("sv", "SE");
BigDecimal pp; //declare variable pp=pounds pence
NumberFormat swedishFormat = NumberFormat.getCurrencyInstance(swedish);
Scanner scan = new Scanner(System.in);
System.out.println("ENTER POUNDS AND PENCE TO AT LEAST FIVE DECIMAL PLACES :");
pp = scan.nextBigDecimal();
BigDecimal pp1 = pp.setScale(2, RoundingMode.HALF_EVEN);
System.out.println("HALF_EVEN: £ " + pp1.toString());
System.out.println(swedishFormat.format(pp1));
BigDecimal pp2 = pp.setScale(2, RoundingMode.FLOOR);
System.out.println("FLOOR: £ " + pp2.toString());
System.out.println(swedishFormat.format(pp2));
BigDecimal pp3 = pp.setScale(2, RoundingMode.CEILING);
System.out.println("CEILING £: " + pp3.toString());
System.out.println(swedishFormat.format(pp3));
BigDecimal pp4 = pp.setScale(2, RoundingMode.HALF_DOWN);
System.out.println("HALF DOWN £: " + pp4.toString());
System.out.println(swedishFormat.format(pp4));
BigDecimal pp5 = pp.setScale(2, RoundingMode.HALF_UP);
System.out.println("HALF UP: £ " + pp5.toString());
System.out.println(swedishFormat.format(pp5));
BigDecimal pp6 = pp.setScale(2, RoundingMode.UP);
System.out.println("UP: £ " + pp6.toString());
System.out.println(swedishFormat.format(pp6));
BigDecimal pp7 = pp.setScale(2, RoundingMode.DOWN);
System.out.println("DOWN: £ " + pp7.toString());
System.out.println(swedishFormat.format(pp7));
BigDecimal pp8 = pp.setScale(2, RoundingMode.UP);
System.out.println("UP: " + pp8.toString());
System.out.println(swedishFormat.format(pp8));
}
}
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This is by design. See the Javadoc:
Rounding mode to assert that the requested operation has an exact result, therefore, no rounding is required. If this rounding mode is specified in an operation that produces an imprecise result, {@code ArithmeticException} is thrown.
This mode is for a specific exception if there is something round.
Examples. The following code does not throw an Exception.
BigDecimal pp = new BigDecimal(7);
pp.setScale(2, RoundingMode.UNNECESSARY);
System.out.println(pp);
changing 7
to a fractional number results in an exception because now you MUST round it:
BigDecimal pp = new BigDecimal(7.1);
pp.setScale(2, RoundingMode.UNNECESSARY);
// java.lang.ArithmeticException: Rounding necessary
System.out.println(pp);
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