What is Inheritance in Java – A Complete Guide

In today’s digital era, Java has emerged as the most widely accessed programming language with robust features. Inheritance is among the key themes of OOPs and Java. This feature enables developers to pass data members and properties from one class to the other. In this blog, let’s explore all about Inheritance in Java its types, how inheritance in java works and what are the advantages and disadvantages associated with it.

Meaning of Inheritance

Inheritance is the foundation of Object-Oriented Programming (OOP). It is the process in Java that allows a class to inherit the methods and fields (characteristics) of another class. Inheritance in Java refers to the process of building new classes from older ones. You can also incorporate additional methods and fields into your existing class.  

What is Inheritance in Java?

When an object inherits from a parent object in Java, it takes on each of the parent object’s attributes 

and behaviors. It is a crucial component of the object-oriented programming system or OOPs. Java’s inheritance system is designed to allow you to build new classes on top of pre-existing ones. When a user inherits from an existing class, they get to use the parent class’s properties and methods.  Now that we know what inheritance in java is, let’s look at why we use inheritance in java.

Why use Inheritance in Java? 

• Code Reuse: All subclasses share the code that was written for the superclass. The code from the parent class can be used directly by the child classes. 
• Method Overriding: The only way to override a method is via inheritance. It is a popular method for achieving Run Time Polymorphism in Java.
• Abstraction: Via inheritance, one can reach the concept of abstraction, which frees us from providing all the details. Abstraction only makes the user aware of the capability.

Terms Used in Inheritance

Let’s take a look at the key terms used in inheritance in java to understand it better.

Class

A class is a collection of objects that have similar traits, behaviors, and attributes. Class does not exist in the actual world. To produce items, it only serves as a model, prototype, or blueprint.

Derived Class

A class that descended from a base class is known as a derived class. It is sometimes referred to as a subclass or a child class. 

Base Class

The primary class from which derived classes inherit their features is called the base class. It is also referred to as the parent class or superclass. 

Reusability

One of the most useful contributions of inheritance in java would be the reusability of a code. The idea of “reusability” is highly supported by java inheritance. For instance, if we wish to construct a new class but an existing one already contains a few of the codes we need, we use the old one to derive the new one. By doing so, you can utilize the methods and fields of the pre-existing class.

Rules of Inheritance Java

By now, you’ve covered the fundamentals of java inheritance in addition to the many types and term used in inheritance. So, let’s go over certain guidelines that we must adhere to while creating applications that use java inheritance.

Rule#1: Java Does Not Support Multiple Inheritance

There’s no way that Java enables multiple inheritances. The Java compiler generates a compilation error whenever the user attempts multiple inheritances in a program. 

Rule#2: Java does not permit Cyclic Inheritance

Cyclic inheritance is where a class inherits itself to a form or structure of a cycle. 

Rule#3: We cannot inherit private data from members

If you know about ‘access modifiers,’ you’ll recall that inheritance isn’t applicable to members with private access.

Rule#4: Constructors are not inherited

The fact that constructors are leveraged for creating class objects means that they aren’t inherited from class to class. 

Rule#5: We can use parent reference to access child objects

You already know quite a lot of inheritance examples. You can make a reference to the parent class type and then use the new keyword to create a derived class object that you’ll assign to the parent class. 

Rule#6: Parent constructors are executed because of super () in derived constructors

According to a rule, it’s clear that the inheritance of constructors isn’t possible. However, the superclass’s constructor could be implemented within the derived class’s constructor, leveraging the super () call. 

Examples of Inheritance in Java

In Java, a class is capable of borrowing attributes and methods from any other class. The term’ child class’ or ‘subclass’ refers to the class that receives the properties by inheritance. The class from which the inheritance of the properties is done is called the parent class or superclass. 

Types of Inheritance in Java 

There are 5 various inheritance in Java, which include: 

• Multi-level inheritance
• Single inheritance
• Hierarchical inheritance
• Multiple inheritances
• Hybrid inheritance

1. Single Inheritance

   In this java inheritance, a single subclass extends from single superclass. Basically, both the parent as well as the child class are present in a single inheritance. The child class - the commonly used one - inherits the data members and methods from the parent class.

2. Multi-Level Inheritance

   In Multi-level inheritance in java, a subclass that extends from a superclass also serves as the superclass for another class in a hierarchical inheritance system.

3. Multiple Inheritance

   The multiple inheritance in java allows a class to have many superclasses and inherit characteristics from all of its parent classes. Be aware that Java does not support multiple inheritances using classes. Only by using interfaces can we obtain multiple inheritances in Java.

4. Hierarchical Inheritance

   In this java inheritance, multiple subclass extends from a superclass. A parent-child relationship is what hierarchical inheritance is. The sole distinction is that several child classes derive from a single-parent class.

5. Hybrid Inheritance

   A seamless combination of inheritance in Java is known as hybrid inheritance. Multiple inheritance types are seen in this form of inheritance. 

Concept of Inheritance in Java

• Class: It is a collection of objects possessing common properties. Objects are made using class – a type of blueprint or template. 

• Child or Sub Class: Also known as an extended or derived class, a child class is a class that inherits another one. 

• Parent or Super Class: The subclass inherits features and capabilities from another class, which is none other than the superclass. It’s also referred to as parent or base class. 

Advantages of Inheritance in Java

Let’s look at the disadvantages of inheritance of java.

1. Code reuse: It is made possible by inheritance, which lowers the amount of new code required. Reduced code duplication results from the subclass’s ability to reuse the superclass’s properties and functions.
2. Abstraction: Through inheritance, it is possible to create abstract classes that specify a common interface for a collection of related classes. This encourages abstraction and encapsulation, making extending and maintaining the code simpler.
3. Class Hierarchy: A class hierarchy can be created through inheritance and utilized to represent the relationships between actual objects in the real world.
4. Polymorphism: Polymorphism, or the capacity for a thing to take on various forms, is made possible by inheritance. The superclass’s methods can be overridden by subclasses, giving them the flexibility to alter how they behave.

Disadvantages of Inheritance in Java

Let’s look at the disadvantages of inheritance of java.

• The performance of the inherited methods lags. 
• A few of the parent class’s data members can be useless, wasting memory as a result.
• A strong connection between child and parent classes is a result of inheritance. This indicates that neither of the two classes (Child or Parent class) may be utilized independently of the other.

Are you interested in knowing about inheritance in Java? If so, explore this article on the various Types of Inheritance in Java! 

Conclusion

This concludes the guide and discussion on inheritance in Java. By now, you must have gained knowledge of the fundamentals of inheritance in Java, including relationships, access modifiers, and more. Now that you have the resources, you may create Java programs that are more reusable, which is a cornerstone of Java OOP (Object Oriented Programming).

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