Checking for NaN and using it in an If

Question

I am collecting some data from a database and adding them together to get some statistics, but since I backdate some of my data then the calculated sum will sometime come up as NaN (not a number) I want to create an if sentence that says if(not a number) then exclude this data from my table.

How do I test if the data (in this case double) is NaN?

Do you care about decimals also? – Metalhead Oct 22 '12 at 12:14 — Metalhead, Oct 22 '12 at 12:14

Bill the Lizard · Accepted Answer · 2018-02-05T19:11:56.923

39

There are static methods Float.isNaN(float) and Double.isNaN(double) that you can use.

double x = ... // whatever calculation you do

if (Double.isNaN(x)) {
    ...
}

edited Feb 05 '18 at 19:11

answered Oct 22 '12 at 12:11

Bill the Lizard

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`x` can be any numeric type or a wrapper of a Number and this will still work. i.e. it doesn't have to be `double`. – Peter Lawrey Oct 22 '12 at 12:45
There is also Float.isNan(x) – Vapid Apr 24 '17 at 19:03
There is also isNaN(x) – Sunny R Gupta Feb 05 '18 at 19:01
@SunnyRGupta Where is that at? – Bill the Lizard Feb 05 '18 at 19:07
1

- OOPS. I did it again. JavaScript mixed in here. There is no isNaN directly. I take back my words. – Sunny R Gupta Feb 05 '18 at 19:23

Peter Lawrey · Answer 2 · 2012-10-22T12:43:51.443

4

You can test for NaN two ways. You can use the built in function

Double.isNaN(x)

or perform the check this does which is

if (x != x)

provided x is a double or a float

edited Oct 22 '12 at 12:43

answered Oct 22 '12 at 12:13

Peter Lawrey

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The second piece of code is only good if x is `double`. If for some reason the code uses `Double` then it will end up comparing reference. – nhahtdh Oct 22 '12 at 12:20
How this works ? That x is double, but Not a Number ? – Damian Leszczyński - Vash Oct 22 '12 at 12:23
@Vash: NaN is very special, it is probably the only thing that when compare not equal to itself will return true. – nhahtdh Oct 22 '12 at 12:24
For those who want to know more: http://stackoverflow.com/questions/2618059/in-java-what-does-nan-mean – Damian Leszczyński - Vash Oct 22 '12 at 12:28

score -6 · Answer 3 · answered Oct 22 '12 at 12:12

-6

This would work for you.

if(number == Float.NaN)

answered Oct 22 '12 at 12:12

Techie Manoj

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This will always be false as NaN != NaN – Peter Lawrey Oct 22 '12 at 12:14
// 1 method if (Double.isNaN(doubleValue)) { } // 2. method if (doubleObject.isNan()) { ... } Simply doing: if (var == Double.NaN) { ... } – Rehan Sarwar Apr 27 '18 at 13:25

Checking for NaN and using it in an If

3 Answers3