A Second Use for super in Java

A Second Use for super

The second form of super acts somewhat like this, except that it always refers to the superclass of the subclass in which it is used. This usage has the following general form:

 

super.member

 

Here, member can be either a method or an instance variable. This second form of super is most applicable to situations in which member names of a subclass hide members by the same name in the superclass.

 

Consider this simple class hierarchy:

 

// Using super to overcome name hiding.

class A {

int i;

}

// Create a subclass by extending class A.

class B extends A {

int i; // this i hides the i in A

B(int a, int b) {

super.i = a; // i in A

i = b; // i in B

}

void show() {

System.out.println("i in superclass: " + super.i);

System.out.println("i in subclass: " + i);

}

}

class UseSuper {

public static void main(String args[]) {

B subOb = new B(1, 2);

subOb.show();

}

}

 

This program displays the following:

 

i in superclass: 1

i in subclass: 2

 

Although the instance variable i in B hides the i in A, super allows access to the i defined in the superclass. As you will see, super can also be used to call methods that are hidden by a subclass.