"super" Keyword in Java
Introduction
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superkeyword is a reference variable in Java. - It is used to refer to the immediate parent class object (i.e., the superclass of the current object).
- This keyword is mainly used in inheritance when a subclass needs to access members (methods, constructors, or variables) of its parent class.
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Use of
superKeyword:- It is used to refer the parent class instance variable.
- It is used to refer to the parent class method.
- It is used to refer to the parent class constructor.
1. It is used to refer the parent class instance variable.
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Java Program Example 1:
class Parent { int num = 100; } class Child extends Parent { int num = 200; void display() { System.out.println("Child num: " + num); System.out.println("Parent num: " + super.num); // referring to parent class variable } } public class SuperDemo { public static void main(String[] args) { Child c = new Child(); c.display(); } }Output:
Child num: 200 Parent num: 100
2. It is used to refer to the parent class method.
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Java Program Example:
class Parent { void showMessage() { System.out.println("Hello from Parent class showMessage() method"); } } class Child extends Parent { void display() { // Calling parent class method using 'super' super.showMessage(); System.out.println("Inside Child class display() method"); } } public class SuperDemo { public static void main(String[] args) { Child obj = new Child(); obj.display(); } }Output:
Hello from Parent class showMessage() method Inside Child class display() method
3. It is used to refer to the parent class constructor.
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Java Program Example:
package notesprogram; class Parent { Parent() { System.out.println("Parent constructor called"); } } class Child extends Parent { Child() { super(); // calls Parent's constructor System.out.println("Child constructor called"); } } public class SuperDemo { public static void main(String[] args) { Child c = new Child(); } }Output:
Parent constructor called Child constructor called
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Note : super() must be the first statement in a constructor
- If used, the call to the parent class constructor (super()) must appear as the very first statement in the child class constructor.
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Note : super() must be the first statement in a constructor
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