Compare Double.MIN_VALUE and 0

Question

Why this code does't work? Actually,this is just the small part of a big program. It has to compare Double.MIN_VALUE to different values, it works with all values except 0. ,why? Thanks!

double d = Double.MIN_VALUE;
if (0. > d) {
    System.out.println("OK");
}

Answer 1

The Double.MIN_VALUE is 4.9E-324. And this is not less than 0. But it is not actually 0.

If you print

System.out.println(4.9E-324d > 0.);//this is true

In this sense,

0.0000000000...0001 != 0. But it tends to 0

The same way 4.9E-324d != 0 but tends to 0

Answer 2

Double.MIN_VALUE is actually a bad name for the constant in Java. It does not fit to int.MIN_VALUE. In C# it is called Double.Epsilon, which IMHO fits better.

So, Double.MIN_VALUE is not the largest negative double value that exists. IMHO there's no such constant for the largest discrete Double number. Otherwise, the largest negative number is Double.NEGATIVE_INFINITY.