Not a Number. A floating point constant representing the result of attempting to perform an erroneous mathematical operation (such as trying to divide by zero). Referencing the static variable Double.NaN prints “NaN”, and calling the non-static method isNaN() on a Float or Double object returns a boolean. For example: return new Float(3.14).isNaN() returns false.
Represents the absence of a value, using the ASCII literal null.