Comparing the values of two generic Numbers

Question

I want to compare to variables, both of type T extends Number. Now I want to know which of the two variables is greater than the other or equal. Unfortunately I

Answer 1

A working (but brittle) solution is something like this:

class NumberComparator implements Comparator {

    public int compare(Number a, Number b){
        return new BigDecimal(a.toString()).compareTo(new BigDecimal(b.toString()));
    }

}

It's still not great, though, since it counts on toString returning a value parsable by BigDecimal (which the standard Java Number classes do, but which the Number contract doesn't demand).

Edit, seven years later: As pointed out in the comments, there are (at least?) three special cases toString can produce that you need to take into regard:

• Infinity, which is greater than everything, except itself to which it is equal
• -Infinity, which is less than everything, except itself to which it is equal
• NaN, which is extremely hairy/impossible to compare since all comparisons with NaN result in false, including checking equality with itself.