Why we got warning when calling a static method through an instance?

[Tahir Akram]

Hi Ranchers;

I have a question.

Why we got warning when calling a static method through an instance of that class?

I mean, the static methods has nothing to do with the object creation of that class, thats why..

Or they are does not contain polymorphic behavior...

Please elaborate.

Thanks.

[Avishkar Nikale]

Hi Tahir,

Please note that though it is legal it is not more readable.

Static method is for a class & not for a instance.

But since a instance will always be a type of that class its legal to call the static method
using the instance reference.

Consider this code

   

Thread t = null;
try 
{
   t.sleep(1000);
} 
catch (InterruptedException e) 
{
  
}

This is confusing since no instance is associated with reference t but still this will not
throw any exception & the current executing thread will sleep.

This will become more clear when you read about threads & static methods used.

As a practice it is good to use the Classname.Staticmethod

[Tahir Akram]

Thanks Avishkar for helping the concept.

[Joanne Neal]

Avishkar Nikale wrote:But since a instance will always be a type of that class its legal to call the static method
using the instance reference.

Not necessarily.
Try this code.

class SuperClass
{
	public SuperClass()
	{
	}

    static void PrintType()
    {
        System.out.println("I'm a SuperClass");
    }
}

class SubClass extends SuperClass
{
    static void PrintType()
    {
        System.out.println("I'm a SubClass");
    }
}

public class StaticTest
{
    public static void main(String[] args)
    {
        SuperClass statictest = new SuperClass();
        statictest.PrintType();
        statictest = new SubClass();
        // type of statictest is SuperClass but it references
        // a SubClass object, so which method will it call ?
        statictest.PrintType();
        SubClass statictest2 = new SubClass();
        statictest2.PrintType();
    }
}

[Avishkar Nikale]

Thanks Joanne,

I should have elaborated that the static method called will depend completely on the reference class type
& not the subsequent class of object the reference is pointing to.

Tahir,

I hope you are not confused by Joanne's example.

It shows that the static method being called will always depend on the class of the reference variable
& not of the underlying instance class.

Please let us know if you need further clarification.