Java Class vs Interfaces

Last Updated : 25 May, 2026

In Java, classes and interfaces are used to define the structure and behavior of programs. While they might seem similar, since both can hold methods and variables, they have very different purposes.

👁 Intefaces-in-Java-1

class-vs-Interface

A class can extend another class and implement an interface, while an interface can only extend another interface, not implement a class.

Class in Java

A class is a blueprint for creating objects. It encapsulates fields (state) and methods (behavior) that are common to all objects of that type.

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Explanation: Above code defines a Student class with two instance variables, id and name, and creates an object to demonstrate default values. It shows that objects of a class can hold state and access its fields.

Interface in Java

An interface in Java is a blueprint of a class. Interface variables are implicitly public static final. Before Java 8, interface methods were implicitly public abstract. From Java 8 onward, interfaces can also contain default and static methods, and from Java 9 onward, private methods are allowed.

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Geek
10

Explanation: Above code defines an interface with a constant and an abstract method, then implements it in a class providing method behavior. It demonstrates how a class can adopt an interface and use its constants and methods.

Class vs Interface

The following table lists all the major differences between an interface and a class in Java.

Features	Class	Interface
Keyword	The keyword used to create a class is "class".	The keyword used to create an interface is "interface".
Instantiation	A class can be instantiated, i.e., objects of a class can be created.	An interface cannot be instantiated directly, instead, it is implemented by a class or a struct.
Inheritance	Classes do not support multiple inheritance.	Interface supports multiple inheritance.
Inheritance Mechanism	A class can inherit another class using the keyword extends.	A class uses implements to adopt an interface, while an interface uses extends to inherit another interface.
Constructors	It can contain constructors.	It cannot contain constructors.
Methods	Methods in a class can be abstract, concrete, or both.	An interface contains abstract methods by default (before Java 8) or default/static methods (from Java 8 onward).
Access Specifiers	Variables and methods in a class can be declared using any access specifier(public, private, default, protected).	Interface variables are public static final, and methods are public by default.
Variables	Variables in a class can be static, final, or neither.	All variables are static and final.
Purpose	A class is a blueprint for creating objects and encapsulates data and behaviour.	An interface specifies a contract for classes to implement by focusing on capabilities rather than implementation.