Comparing numbers is hard

afish — Sat, 17 Aug 2019 08:00:21 +0000

We know that to compare floating point values we should use epsilon and not just compare bits. We may run into similar issues when comparing BigDecimal in Java:

BigDecimal a = BigDecimal.valueOf(0);
BigDecimal b = BigDecimal.valueOf(Double.valueOf(0));
System.out.println(a.equals(b));

What is the output? Of course it is false, otherwise I wouldn’t write this post. This is because BigDecimal includes scale:

Unlike compareTo, this method considers two BigDecimal objects equal only if they are equal in value and scale (thus 2.0 is not equal to 2.00 when compared by this method).

So we should use this:

System.out.println(a.compareTo(b));

and then the result is as we expect.

BigDecimal – Random IT Utensils

Comparing numbers is hard