NaN = Not A Number
Not A Number
"NaN" stands for "not a number". "Nan" is produced if a floating point operation has some input parameters that cause the operation to produce some undefined result. For example, 0.0 divided by 0.0 is arithmetically undefined. Taking the square root of a negative number is also undefined.
0.0 / 0.0 -> NaN
Math.sqrt(-2.0) -> NaN
Operations involving NaN
Double.NaN + Double.NaN -> NaN
Float.NaN + 2.0 -> NaN
Float.NaN * 3.0 -> NaN
(0.0 / 0.0) * Float.POSITIVE_INFINITY -> NaN
Math.abs(0.0 / 0.0) -> NaN
(int) (Double.NaN) -> 0
All boolean operations involving "NaN" results in a false value.
Double.NaN > 1.0 -> false
Double.NaN < 1.0 -> false
Double.NaN == 1.0 -> false
Float.NaN < -3.0 -> false
Float.NaN > Float.POSITIVE_INFINITY -> false
Float.NaN < Float.POSITIVE_INFINITY -> false
(0.0 / 0.0) == (0.0 / 0.0) -> false
Taken from http://www.concentric.net/~Ttwang/tech/javafloat.htm