Use Float.isNaN(float) or Double.isNaN(double) to check NaN value : float « Java Source And Data Type « SCJP

1. SCJP
2. Java Source And Data Type
3. float

public class MainClass{
    public static void main(String[] argv){
        float x = Float.NaN;
        
        System.out.println( Float.isNaN(x));
    }
}