#   
## Overview

The **`isNaN()` method** of the Java `Double` class returns `true` if the specified number is a **NaN** (Not-a-Number) value. Otherwise, it returns `false`.

`Double` is defined in the `lang` package in Java. 

#   
## Method Signature

```Java
public static boolean isNaN(double v)
```

## Parameters 
`double v`: the value to be tested.

#   
## Example

In the code below, we define three different double variables, each the result of a different computation. Then, we use the `isNaN()` method of `Double` class to test the result for `NaN`.

import java.lang.Double;

public class Main {

    public static void main(String args[])
    {
        Double d1 = 100 / 0.0;
        Double d2 = 0 - 0.0;
        Double d3 = 100 * 0 / 0.0;
        System.out.println(d1 +" - " + d1.isNaN());
        System.out.println(d2 +" - " + d2.isNaN());
        System.out.println(d3 +" - " + d3.isNaN());
    }
}

What is Double.isNan() in Java?

Double's isNaN() method checks if a double value is NaN (Not-a-Number), returning true if it is.