Thread: Isn't the result supposed to be 6?

public class Examp {
    public static void main(String[] args) {
       int i = 5;
       Examp examp_object = new Examp();
       examp_object.inc(i);
       System.out.println(i);
 
    }
    public void inc (int k) {
	k++;
    }
 
}

For my surprise, the result is appearing to be 5. Why is that?

Originally Posted by obel1x

public class Examp {
    public static void main(String[] args) {
       int i = 5;
       Examp examp_object = new Examp();
       examp_object.inc(i);
       System.out.println(i);
 
    }
    public void inc (int k) {
	k++;
    }
 
}

For my surprise, the result is appearing to be 5. Why is that?

I'm kind of struggling with something similar, but in this case, I think what is happening is that you are sending the argument of i to the method inc. The method is then updating a local variable of the object examp_object which is actually an instance of itself, so i never actually changes because when you call the object which is the main method you end up resetting i back to 5?

It's helpful in these little study programs to 1) make them as simple as possible, and 2) to over-instrument them to see what's going on. To simplify, eliminate the instance creation. It doesn't add to the study. To over-instrument, add a few print statements to check the values of variables of interest. In the end, something like:

public class TestClass
{
    public static void main(String[] args)
    {
       int i = 5;
       inc(i);
       System.out.println( "i in main() = " + i );
 
    } // end method main()
 
    public static void inc ( int k )
    {
        k++;
        System.out.println( "k in inc() = " + k );
 
    } // end method inc()
 
} // end class TestClass