Inheritence

Inheritance

Inheritance allows one class (child class) to inherit the properties and methods of another class (parent class). It supports reusability and method overriding.

Types of Inheritance

• Single Inheritance: One child class inherits from one parent class.
• Multilevel Inheritance: A child class inherits from a parent class, which itself is a child of another class.
• Hierarchical Inheritance: Multiple child classes inherit from one parent class.
• Hybrid Inheritance: Combination of different inheritance types (not directly supported in Java but achieved using interfaces).

// Example of Single Inheritance
class Animal {
    void eat() {
        System.out.println("This animal eats food");
    }
}

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

Super Keyword

The 'super' keyword refers to the immediate parent class. It is used to access parent class methods, constructors, and variables.

class Parent {
    void display() {
        System.out.println("Parent class method");
    }
}

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

Method Overriding

Method overriding occurs when a child class provides its own implementation of a method already defined in its parent class.

class Vehicle {
    void run() {
        System.out.println("Vehicle is running");
    }
}

class Bike extends Vehicle {
    void run() {
        System.out.println("Bike is running safely");
    }
}

Covariant Return Type

In method overriding, a child class can return a subtype of the parent class's return type. This is called a covariant return type.

class Parent {
    Parent get() {
        return this;
    }
}

class Child extends Parent {
    @Override
    Child get() {  // Covariant return type
        return this;
    }
}

Abstract Class

An abstract class cannot be instantiated directly. It can have abstract methods (methods without a body) and concrete methods.

abstract class Shape {
    abstract void draw(); // Abstract method (no body)

    void message() {
        System.out.println("This is a shape");
    }
}

class Circle extends Shape {
    void draw() {
        System.out.println("Drawing a circle");
    }
}

Viva/Interview Questions (Inheritance & Related Concepts)