Java - using the 'super' keyword

Question

Simple question. I made a class called Tester1 which extends another called Tester2. Tester2 contains a public string called 'ABC'.

Here is Tester1:

public class Tester1 extends Tester2
{
    public Tester1()
    {
         ABC = "Hello";
    }
}

If I instead change line 5 to

super.ABC = "Hello"; 

am I still doing the exact same thing?

Answer 1

Yes. There's only one ABC variable within your object. But please don't make fields public in the first place. Fields should pretty much always be private.

If you declared a variable ABC within Tester1 as well, then there'd be a difference - the field in Tester1 would hide the field in Tester2, but using super you'd still be referring to the field within Tester2. But don't do that, either - hiding variables is a really quick way to make code unmaintainable.

Sample code:

// Please don't write code like this. It's horrible.
class Super {
   public int x;
}

class Sub extends Super {
    public int x;

    public Sub() {
        x = 10;
        super.x = 5;
    }

}

public class Test {
    public static void main(String[] args) {
        Sub sub = new Sub();
        Super sup = sub;
        System.out.println(sub.x); // Prints 10
        System.out.println(sup.x); // Prints 5
    }
}

Answer 2

Yes, the super qualifier is unnecessary but works the same. To clarify:

public static class Fruit {

    protected String color;
    protected static int count;
}

public static class Apple extends Fruit {

    public Apple() {
        color = "red";
        super.color = "red"; // Works the same
        count++;
        super.count++; // Works the same
    }
}