Question

I know that interface can have only static and final values implemented inside it.. But is there any loophole by which I can change the value of
a variable using interface?? The question may be absurd, but I m helpless since its my requirement. Here is the example piece of code..

public interface I {
    int val = 1;  
    int changeValue();

}

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Class A implements I{
    int changeValue(){
        val = 2 ; 
        return 0;
    }
}

How to change the value of ‘val’ using interface?
Can I do something similar to:

val = changeValue();

Is there anything equivalent to do this functionality in an interface?

Answer 1

You cannot. Interface variables are static and final by default.

A final variable is a variable that cannot be changed during the life of the object.

A static vairable is a class variable – it means there is only one value of it for all instances of the class (or interface in this case).

Thus – you only have one value for I.x – and this value cannot be changed.

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What you might want to do, is define methods in your interface:

int getVal();
void setVal(int val);

And make the implementing classes implement the methods – so you will be able to use the variable with the getVal() and setVal() methods.