1. Introduction to Inheritance

1.1 What is Inheritance

Inheritance is a mechanism where one class acquires properties and methods of another class.

1.2 Why Use Inheritance

Code reuse
Reduces redundancy
Improves maintainability

1.3 Real-World Example

Parent → Animal
Child → Dog

1.4 Syntax

class Parent {
    // properties and methods
}class Child extends Parent {
    // additional features
}

2. Types of Inheritance

2.1 Single Inheritance

One class inherits from one parent.

class A {}
class B extends A {}

2.2 Multilevel Inheritance

A chain of inheritance.

class A {}
class B extends A {}
class C extends B {}

2.3 Hierarchical Inheritance

Multiple classes inherit from one parent.

class A {}
class B extends A {}
class C extends A {}

2.4 Multiple Inheritance (Concept)

Java does not support multiple inheritance with classes.

2.5 Hybrid Inheritance

Combination of different types (not directly supported with classes).

3. Method Overriding

3.1 Definition

Method overriding allows a subclass to provide a specific implementation of a method already defined in the parent class.

3.2 Example

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

3.3 Rules

Same method name
Same parameters
Same return type

3.4 @Override Annotation

@Override
void sound() {
    System.out.println("Dog barks");
}

3.5 Runtime Polymorphism

Method is decided at runtime based on object.

4. super Keyword

4.1 Definition

The super keyword refers to the parent class object.

4.2 Access Parent Variable

super.variableName;

4.3 Call Parent Method

super.methodName();

4.4 Call Parent Constructor

super();

4.5 Example

class Animal {
    void show() {
        System.out.println("Animal class");
    }
}class Dog extends Animal {
    void show() {
        super.show();
        System.out.println("Dog class");
    }
}

5. final Keyword

5.1 Definition

The final keyword is used to restrict changes.

5.2 final Variable

final int MAX = 100;

5.3 final Method

final void display() {}

Cannot be overridden.

5.4 final Class

final class A {}

Cannot be extended.

5.5 Example

final class Animal {}class Dog extends Animal {} // Error

Conclusion

Inheritance is a powerful feature in Java that allows code reuse and better organization of programs. By understanding inheritance types, method overriding, and keywords like super and final, beginners can build efficient and scalable applications.

Inheritance