How to Use Java Inner Class to Your Advantage?

Since inner classes were introduced in version 1.1 of Java, they have triggered a lot of different opinions among people. Knowing when to use inner classes is crucial because using it on wrong situations can create code that is hard to understand and maintain. This article provides facts on how you can use Java inner class to your advantage. It can also be helpful to candidates preparing for an interview.

What Is Inner Class in Java?

Inner classes, also referred to as nested classes, are classes that exist within other classes. They are members of their enclosing class. The nesting is a relationship between classes rather than objects. Java nested class is, therefore, group into as public package meaning it has no access modifier or protected and private, implying that it has access modifiers.

The primary purpose of a nested class is to group classes in one place so that it can be easy to read and maintain.

Using Java Inner Class to Your Advantage

Here are a few tips on how to use the inner class in Java:

Develop Easily Readable and Maintainable Code

Inner classes are embedded into the outer class when the inner class is to be used by one class, making the package more streamlined. Since the classes and interfaces are placed in a single location, you can seamlessly read and maintain the code.

Increase the Level of Encapsulation

The inner class has a unique relationship with the outer class. The inner class can gain access to all members of the outer class including private while maintaining its type of class. You can hide an inner class from other classes of the same package and still access to all members of the enclosing class. You can, therefore, make the inner class of the outer class members private as well as hide the inner class members from other classes of the same package. This increases the level of encapsulation.

Optimize Your Code

This means that you will need less code to write when using inner class in Java. When a class A is written and needs another class B for its use, there are two ways to achieve this. You can either write an inner class B into class A or write class B separately. The good thing about writing inner class B in class A is that you avoid having a different class altogether.

Inner class comes in handy when implementing a helper class or in event handling mechanism. When you use inner class for event handling, you eliminate the need for selecting the component. Inner classes allocate an event handler for every component and every handler completely knows the component it is working for.

Note: Since you’re here, you might also be interested in how to reverse a linked list in Java┬áplus our collection of Java interview questions!


You can typically use Java inner class to increase encapsulation, optimize code and develop more readable and maintainable code. We hope that this article has given you a clear explanation on how to use inner class to your advantage. This knowledge can surely help if you encounter the question in an interview. Let us know your thoughts about this answer.