Organizing Classes and Interface in Java?

Organizing Classes and Interface in Java?

Programming languages have become dynamic, object-oriented, and most important as the other languages because IT industries are all about software that contains coding. The main languages in programming are Java, Python, C++, C#, and many more. Moreover, in our previous articles, we have already discussed what is Java and the concept of OOPS in Java. Today’s article is all about how you can organize classes and interface in Java. But firstly, further, any delay lets discuss what is an interface in Java.

What is Interface in Java?

In the Java programming language, an Interface is an abstract method used to define the performance that a class should carry out. It also contains other methods like default methods, static methods, and constant definitions. The object to be implemented in the interface should be either null or be bound. Moreover, Interfaces can easily stimulate multiple inheritances. However, back in Java 8, we could only use the default and static method in an interface and now in Java 9, we can have private methods. To use the interface in Java always enter the keyword Interface.

Why use Interface in Java?

  • Firstly, Interfaces stimulate multiple inheritances.
  • It can attain the loose coupling.
  • Lastly, It can execute the abstraction.

Changes in Java 9 Interface 

Latest to Java 9 Interface it has introduced Private methods and Private Static methods. These methods can improve the code-reusability in the interface and only accessible from an interface to another interface or class. In Java 9, there are six different methods and variables  of the interface:

  1. Abstract methods
  2. Default methods
  3. Static methods
  4. Private methods
  5. Private Static methods
  6. Constant variables

Also read: JSTL

What are Classes in Java?

It is the collection of classes in the Java program which is provided by the Java language technology tools and the users. Java is all about objects and is an example of Java class. Moreover, it can create many objects in the same class and also you can write your own classes 

Important Component of Classes in Java

  • Constructors: This method can be used to start the object and have no return value.
  • Instance Variables: It can be used to store the object information.
  • Methods: It is used to perform the operations related to the object in the Java class.
  • Static Variables: It gives all the information related to the Java class.
  • Static Methods: It operates only the class, not the object.

Creating Classes in Java

  1. Firstly, to create the class you need to keep the component which consists of data such as for instance variables and it should be a private class.
  2. To access the private component of data in a class we can use Accessor methods also called public methods. 
  3. Further, to get or to set the value from the private component variable we can use the Accessor method.
  4. Lastly, it gives the programmer complete control over the actions performed in the class as well as to change the component variable. Java Encapsulation is a concept of OOPS.

Types of Classes

There are two types of class in java:

  • Abstract Class: These classes do not have any code and are incomplete classes. Hence, you cannot create an object of this class and can only use it for completing the details.
  • Non-Abstract class: These are complete classes and have code. So, you can easily create an object of the class.

Class vs Interface in Java

In Class, with the help of instance variable, you can create an object, but in an Interface, besides not having any instance variable you can create an object. A class contains concrete with having implementation methods. However, an Interface cannot concrete with the implementation methods. The class has private, protected, and public access specifiers and Interface has only one public specifier.

Relationship between Classes and Interfaces in Java

  • The class extends Class.
  • The interface extends Interface.
  • Class implement Interface.
Interface and class relation
Interface and class relation


In conclusion, the Code that is written using an interface is easier to test because you can easily supply a mock implementation instead of a real one. You can also learn Java programming online to make the concept more clear. As of here, we have learned how classes and interfaces play an important role in Java. Classes in java are the blueprint of the objects and as in terms of multiple inheritances class does not support it. However, interfaces can achieve multiple inheritances and facilitate polymorphism. 


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