Inheritance in java

The process by which one class acquires the properties(data members) and functionalities(methods) of another class is called inheritance.

Inheritance allows us to reuse code, it improves re-usability in your java application.

Note: The biggest advantage of Inheritance is that the code that is already present in base class need not be rewritten in the child class.

Single Inheritance

class Animal {
	public void eat() {
		System.out.println("I can eat");
	}

	public void sleep() {
		System.out.println("I can sleep");
	}
}
class Dog extends Animal {
	public void bark() {
		System.out.println("I can bark");
	}
}

public class Helloworld {
	public static void main(String[] args) {
	      Dog dog1 = new Dog();
	      dog1.eat();
	      dog1.sleep();
	      dog1.bark();
	}
}

We have created a parent class called Animal and then we created a child class Dog.

When we extend the Animal class in Dog class at that time the dog class has the availability to

access all the methods and variables.

Output:

I can eat

I can sleep

I can bark

As in output, you can see the dog object is able to access the eat and sleep methods which are inside the Animal class.

Multi-Level Inheritance

From the same as above example we have created a new class called BabyDog. Added a new method ,

so while accessing the parent methods we do not face any issues because of multilevel inheritance.

class Animal {
	public void eat() {
		System.out.println("I can eat");
	}

	public void sleep() {
		System.out.println("I can sleep");
	}
}
class Dog extends Animal {
	public void bark() {
		System.out.println("I can bark");
	}
}
class BabyDog extends Dog {
	public void introduce() {
		System.out.println("I am BabyDog");
	}
}

public class Helloworld {
	public static void main(String[] args) {
		BabyDog dog1 = new BabyDog();
		dog1.eat();
		dog1.sleep();
		dog1.bark();
		dog1.introduce();
	}
}

Output:

I can eat I can sleep I can bark I am BabyDog

Hierarchical inheritance

class Animal{
	public void eat() {
		System.out.println("i can eat");
	}
}
class Dog extends Animal{
	public void bark() {
		System.out.println("i can bark");
	}
}
class BabyDog extends Animal{
	public void introduce() {
		System.out.println("i am baby dog");
	}
}
public class Hierarchical {

	public static void main(String[] args) {
		BabyDog babyDog= new BabyDog();
		babyDog.eat();
		babyDog.introduce();
	}

}