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Double isNaN() method in Java with examples

Double isNaN() method in Java with examples

Last Updated : 11 Jul, 2025

The

isNaN()

method of

Java Double class

is a built in method in Java returns true if this Double value or the specified double value is Not-a-Number (NaN), or false otherwise.

Syntax

:

public boolean isNaN()
        or
public static boolean isNaN(double val)
Parameters

: The function accepts a single parameter

val

which specifies the value to be checked when called directly with the Double class as static method. The parameter is not required when the method is used as instance method.

Return Value:

It returns

true

if the val is

NaN

else it return

false

. Below programs illustrate

isNaN()

method in Java:

Program 1: Java
// Java code to demonstrate
// Double isNaN() method
// without parameter

class GFG {
    public static void main(String[] args)
    {

        // first example
        Double f1 = new Double(1.0 / 0.0);

        boolean res = f1.isNaN();

        // printing the output
        if (res)
            System.out.println(f1 + " is NaN");
        else
            System.out.println(f1 + " is not NaN");

        // second example
        f1 = new Double(0.0 / 0.0);

        res = f1.isNaN();

        // printing the output
        if (res)
            System.out.println(f1 + " is NaN");
        else
            System.out.println(f1 + " is not NaN");
    }
}
Output:
Infinity is not NaN
NaN is NaN
Program 2: Java
// Java code to demonstrate
// Double isNaN() method
// with parameter

class GFG {
    public static void main(String[] args)
    {

        // first example
        Double f1 = new Double(1.0 / 0.0);

        boolean res = f1.isNaN(f1);

        // printing the output
        if (res)
            System.out.println(f1 + " is NaN");
        else
            System.out.println(f1 + " is not NaN");

        // second example
        f1 = new Double(0.0 / 0.0);

        res = f1.isNaN(f1);

        // printing the output
        if (res)
            System.out.println(f1 + " is NaN");
        else
            System.out.println(f1 + " is not NaN");
    }
}
Output:
Infinity is not NaN
NaN is NaN
Reference: https://docs.oracle.com/javase/7/docs/api/java/lang/Float.html#isNaN()

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