When to Use the "super" Keyword in Java

When can you use the "super" keyword In Java?

In Java, the super keyword is used in several contexts, primarily to refer to the superclass of the current object. Here are the main scenarios where you can use the super keyword:

1. Accessing Superclass Methods: You can use super to call a method from the superclass that has been overridden in the subclass. This is useful when you want to invoke the superclass's version of the method.

   class Parent {
       void display() {
           System.out.println("Parent display");
       }
   }
   
   class Child extends Parent {
       void display() {
           super.display(); // Calls the Parent's display method
           System.out.println("Child display");
       }
   }
   

2. Accessing Superclass Constructors: You can use super() to call a constructor of the superclass from the subclass constructor. This must be the first statement in the subclass constructor.

   class Parent {
       Parent() {
           System.out.println("Parent constructor");
       }
   }
   
   class Child extends Parent {
       Child() {
           super(); // Calls the Parent's constructor
           System.out.println("Child constructor");
       }
   }
   

3. Accessing Superclass Fields: If a subclass has a field with the same name as a field in its superclass, you can use super to refer to the superclass's field.

   class Parent {
       int value = 10;
   }
   
   class Child extends Parent {
       int value = 20;
   
       void display() {
           System.out.println("Child value: " + value); // Refers to Child's value
           System.out.println("Parent value: " + super.value); // Refers to Parent's value
       }
   }
   

Summary

• Use super.methodName() to call a method from the superclass.
• Use super() to call a superclass constructor.
• Use super.fieldName to access a field from the superclass when there is a naming conflict.

These usages help in managing inheritance and ensuring that the correct methods and fields are accessed in a class hierarchy.