Loopy Puzzlers - Java Puzzlers: Traps, Pitfalls, and Corner Cases - page 78

example, this program prints false :
class Test {
public static void main(String[] args) {
double i = 0.0 / 0.0;
System.out.println(i - i == 0);
}
}
The principle underlying the rules for computing with NaN is that once it generates NaN, a
computation is damaged, and no further computation can repair the damage. The NaN value is
intended to allow a damaged computation to proceed to a point where it is convenient to deal with
the situation.
In summary, the float and double types have a special NaN value to represent a quantity that is not
a number. The rules for computations involving NaN are simple and sensible, but the consequences
of these rules can be counterintuitive.
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