why Float.NaN == Float.NaN is false

Question

Why Float.NaN == Float.NaN gives false ? I have tested it on more than one JVMs.

Any help is appreciated .

  System.out.println(Float.NaN == Float.NaN); // gives false

Find the reason [here](http://stackoverflow.com/questions/9341653/float-nan-float-nan) — Jayamohan, Apr 08 '13 at 11:52
Off the top of my head I'm thinking `NaN` is specified to be unequal to any other number. (Or, in fact, *uncomparable*, but `==` can't express that.) — millimoose, Apr 08 '13 at 11:56

Denys Séguret · Answer 1 · 2013-04-08T12:01:20.240

3

That's not specific to Java.

IEEE754's NaN are by contract equal to no number, even themselves.

edited Apr 08 '13 at 12:01

answered Apr 08 '13 at 11:51

Denys Séguret

isn't that the easiest way to detect NaN - if the number is not itself? – Tobias Langner Apr 08 '13 at 12:00
@TobiasLangner As put by Wikipedia : *"The equality and inequality predicates are non-signaling so x = x returning false can be used to test if x is a quiet NaN"*. But in your code the clearest would be to use `Float.isNaN`. – Denys Séguret Apr 08 '13 at 12:01

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