How do you test to see if a double is equal to NaN in Java?

Use the static Double.isNaN(double) method, or your Double's .isNaN() method.

Simply doing:

if (var == Double.NaN) {
    ...
}

Reference:
http://stackoverflow.com/questions/1456566/how-do-you-test-to-see-if-a-double-is-equal-to-nan-in-java