What is the Difference Between Class and Interface?

06/21/2025 • Giovanni Medeiros

The main difference between a class and an interface in Java is that a class describes the behavior of an object, while an interface contains the behaviors assigned and defined by the class. Here are some key differences between classes and interfaces:

  • Keyword: A class is created using the keyword class, while an interface is created using the keyword interface.
  • Objects: Classes can have objects created from them, while interfaces cannot.
  • Method Bodies: Classes can contain method bodies, while interfaces can only contain method signatures (i.e., abstract methods).
  • Inheritance: Classes can inherit from other classes using the extends keyword, while interfaces can be inherited by classes using the implements keyword.
  • Variables: Classes can have different types of variables (instance, static, final), while interface variables are always public, static, and final.
  • Constructors: Classes can have constructor methods, while interfaces cannot.

In summary, classes are used to create objects and contain method bodies, while interfaces are used to define the capabilities that a class must implement. An interface is a blueprint of a class, specifying the methods and properties that a class implementing the interface must have.

Comparative Table: Class vs Interface

Here is a table comparing the differences between a class and an interface:

Parameter Class Interface
Keyword used class interface
Objects can be created Yes No
Inheritance A class can extend another class A class can implement an interface
Inherited by A class can be extended by another class A class can implement multiple interfaces
Constructors Yes, a class can contain constructors No, an interface cannot contain constructors
Abstract methods No, a class cannot contain abstract methods Yes, an interface can contain abstract methods
Access specifiers Variables and methods in a class can be declared using any access specifier (public, private, protected, default) All variables and methods in an interface are declared as public
Variables Variables in a class can be static, final, or neither All variables in an interface are static and final

In summary, a class is a blueprint for creating objects and can contain constructors, non-abstract methods, and variables with various access specifiers. An interface, on the other hand, is a contract that a class agrees to implement, containing abstract methods and public variables. Classes can extend other classes and implement interfaces, while interfaces can extend other interfaces and be implemented by classes.

Read more