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What is Inheritance?

Inheritance allows one class (child) to acquire properties and behaviors (fields and methods) of another class (parent).
It's like "Child inherits features from Parent".

Syntax

    
    class Parent {
        // fields and methods
    }

    class Child extends Parent {
        // additional fields and methods
    }
    
    

extends keyword is used to inherit from a class.

Example:

    
    // Parent class
    class Animal {
        void eat() {
            System.out.println("This animal eats food.");
        }
    }

    // Child class
    class Dog extends Animal {
        void bark() {
            System.out.println("Dog barks.");
        }
    }

    // Main class
    public class Main {
        public static void main(String[] args) {
            Dog d = new Dog();
            d.eat();   // inherited method
            d.bark();  // own method
        }
    }
    
    

Output:

    
    This animal eats food.
    Dog barks.
    
    

Why use Inheritance?

• Reusability: Avoid writing the same code again.
• Extensibility: Easily add new features.
• Readability: Code structure becomes more logical.

Types of Inheritance in Java

Type	Supported in Java?	Example
Single	Yes	One child → one parent
Multilevel	Yes	Class C inherits from B, B from A
Hierarchical	Yes	Multiple classes inherit from one parent
Multiple (direct)	No	Java doesn't support this (but you can use interfaces)

Multilevel Example

    
    class A {
        void displayA() {
            System.out.println("A class");
        }
    }

    class B extends A {
        void displayB() {
            System.out.println("B class");
        }
    }

    class C extends B {
        void displayC() {
            System.out.println("C class");
        }
    }

    public class Test {
        public static void main(String[] args) {
            C obj = new C();
            obj.displayA();  // from A
            obj.displayB();  // from B
            obj.displayC();  // from C
        }
    }
    
    

super Keyword (used in Inheritance)

• super is used to refer to the parent class.
• You can use it to:
  • Call parent class methods: super.methodName();
  • Call parent class constructor: super();

Example:

    
    class Animal {
        Animal() {
            System.out.println("Animal constructor");
        }
    }

    class Dog extends Animal {
        Dog() {
            super(); // calls parent constructor
            System.out.println("Dog constructor");
        }
    }
    
    

Access Modifiers in Inheritance

Modifier	Inherited in Child?
public	Yes
protected	Yes
private	No
default (no modifier)	Only in same package

"Inheritance = Parent gives code to child. Child gets all the features and adds new ones too."

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