Explain forms of inheritance in java with examples?

Answer 1

Types of Inheritance:

They are:

1. Single Inheritance

A Scenario where one class is inheriting/extending the behavior of just one super class.

Ex: public class Ferrari extends Car {…}

2. Multilevel Inheritance

A Scenario where one class is inheriting/extending the bahavior of another class which in turn is inheriting behavior from yet another class.

Ex: public class Automobile {…}

Public class Car extends Automobile {…}

Public class Ferrari extends Car {…}

This multilevel inheritance actually has no limitations on the number of levels it can go. So as far as java goes, it is limitless. But for maintenance and ease of use sakes it is better to keep the inheritance levels to a single digit number.

3. Multiple Inheritance

Actually, java does not support multiple inheritance. You can achieve partial multiple inheritance using interfaces but java is not like C or C++ where you can do direct multiple inheritance. However, you can achieve partial multiple inheritance with the help of interfaces.

Ex: public class FerrariF12011 extends Ferrari implements Car, Automobile {…}

And this is under the assumption that Car and Automobile are interfaces.

Here if you see, though you don't inherit concrete code from the Car or the Automobile interface, you do inherit skeleton methods that determine the way your class eventually behaves and hence this can be considered partial Multiple Inheritance.

If you are curious asking me why doesn't java allow multiple inheritance, think about this scenario. Let us say the Automobile Class has a drive() method and the Car class has a drive() method and the Ferrari class has a drive() method too. Let us say you create a new class FerrariF12011 that looks like below:

Public class FerrariF12011 extends Ferrari, Car, Automobile {…}

And at some point of time you need to call the drive() method, what would happen? Your JVM wouldn't know which method to invoke and you may have to instantiate one of the classes that you already inherit in order to call its appropriate method. Sounds confusing right? To avoid this nonsense is why the creators of java did not include this direct multiple inheritance feature.

4. Hybrid Inheritance

This is the scenario wherein your java code exhibits traits of more than one of the inheritance types explained above. Going with the example above again:

Public class FerrariF12011 extends Ferrari implements Car, Automobile {…}

The above is a combination of both single and multiple inheritance.