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Java Double class isNaN() method with example

Double class isNaN() method: Here, we are going to learn about the isNaN() method of Double class with its syntax and example.
Submitted by Preeti Jain, on September 22, 2019


    public boolean isNaN ();
    public static boolean isNaN(double value);

Double class isNaN() method

  • isNaN() method is available in java.lang package.
  • isNaN() method is used to check NaN (Not a Number) values (i.e. either positive NaN or negative NaN).
  • isNaN(double value) method is used to check NaN values for the given double argument (i.e. either positive or negative NaN).
  • isNaN() method does not throw an exception at the time of checking NaN values represented by the object.
  • Similarly, isNaN(double value) method does not throw an exception at the time of checking NaN values of the given argument.
  • Both types of methods are the non-static methods, they are accessible with the class object only and if we try to access them with the class name then we will get an error.


  • In the first case isNaN(), we don't pass any parameter or value.
  • In the second case isNaN(double value), we pass only one parameter of double type, it represents the double value to be tested for NaN.

Return value:

The return type of this method is boolean, it returns wither "true" if the value if either positive or negative NaN, it returns "false" if the value is not NaN.


// Java program to demonstrate the example 
// of isNaN() method of Double class

public class IsNaNOfDoubleClass {
    public static void main(String[] args) {
        // Object initialization
        Double ob1 = new Double(0.0 / 0.0);
        Double ob2 = new Double(-0.0 / 0.0);
        Double ob3 = new Double(20.0);

        // Display ob1,ob2 and ob3 values
        System.out.println("ob1: " + ob1);
        System.out.println("ob2: " + ob2);
        System.out.println("ob3: " + ob3);

        // It checks NaN by calling ob1.isNaN() for ob1
        // and ob2.isNaN() for ob2  
        boolean NaN1 = ob1.isNaN();
        boolean NaN2 = ob2.isNaN();

        // It also checks NaN of this Double object by calling
        // ob3.isNaN(ob3) for ob3 
        boolean NOTNaN = ob3.isNaN(ob3);

        // Display result values
        System.out.println("ob1.isNaN(): " + NaN1);
        System.out.println("ob2.isNaN(): " + NaN2);
        System.out.println("ob3.isNaN(ob3): " + NOTNaN);


ob1: NaN
ob2: NaN
ob3: 20.0
ob1.isNaN(): true
ob2.isNaN(): true
ob3.isNaN(ob3): false

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