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Calling a method using null in Java
  • Difficulty Level : Easy
  • Last Updated : 29 Oct, 2017

Prerequisite: null in Java, Static in Java

Can you predict the output of the following program??
Before answering, please observe the fact that in given code, fun() is a static member that belongs to the class and not to any instance.




// Java program to illustrate calling
// static method using Null
public class GFG {
    public static void fun()
    {
        System.out.println("Welcome to GeeksforGeeks!!");
    }
  
    public static void main(String[] args)
    {
        ((GFG)null).fun();
    }
}

Output:

Welcome to GeeksforGeeks!!

Explanation:
This program looks as though it is ought to throw a NullPointerException. However, the main method invokes the greet method (fun) on the constant null, and you can’t invoke a method on null.
But, when you run the program, it prints “Welcome to GeeksforGeeks!!”. Let’s see how:

  • The key to understanding this puzzle is that GFG.fun is a static method.
  • Although, it is a bad idea to use an expression as the qualifier in a static method invocation, but that is exactly what this program does.
  • Not only does the run-time type of the object referenced by the expression’s value play no role in determining which method gets invoked, but also the identity of the object, if any, plays no role.
  • In this case, there is no object, but that makes no difference. A qualifying expression for a static method invocation is evaluated, but its value is ignored. There is no requirement that the value be non-null.

This article is contributed by Shubham Juneja. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

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