What is the Difference Between Class and Interface?

06/01/2025 • 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.

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