CODEWITHSUNDEEP
javastatic
Batty
Batty

Reputation: 151

Static variable accessed from null variable

Why is a null reference exception not thrown when I try to print the value of a static field value from an uninitialized instance of a class.

I expected a Null reference exception in the following code:

public class Check {

  static int i=1;

  public static void main(String []args)
  {
     Check ch = null;
     System.out.print(ch.i);
  }

}

Produces output as: 1.

Upvotes: 2

Views: 76

Answers (3)

adibro500
adibro500

Reputation: 171

In your snippet, i is static that means it may not need to be instantiated that means the default constructor need not be called as:

Check ch= new Check();

as i is static only a reference will suffice. Like you did,

Check ch = null;

So doing,

System.out.println(ch.i);

will print the value of i that is 1 from static context

Upvotes: 2

lealceldeiro
lealceldeiro

Reputation: 14958

Given that i is static (it can be accessed through the class directly, no need to use an instance for it), in the code ch.i, the compiler checks for the type of the reference of ch (Check) and use it for accessing the variable i instead of using the class instance. This mean null (the instance) is not used at all (thus we don't get any exception).

That's it, the output of Check.i is 1.

Upvotes: 1

Alexandre
Alexandre

Reputation: 589

Because i is a static variable, it does not matter whether its value is obtained from an object or from the class.

See the note here:

https://docs.oracle.com/javase/tutorial/java/javaOO/classvars.html

Upvotes: 1

Related Questions