Difference interface vs abstract class in java

Difference interface vs abstract class in java

In this tutorial, we will learn about:
  • difference between abstract class and interface in java

Abstract class and interface differ based on following parameters:
  • An abstract class can have both abstract methods and concrete methods.
  • An interface has all the methods as abstract. Methods in interface is 100% abstract.
Keyword used to declare
  • To declare abstract class use the keyword ‘abstract’.
  • To declare interface use the word ‘interface’. 
Method declaration
  • In abstract class, to declare any method as abstract use of abstract keyword is mandatory.
  • In interface, to declare methods as abstract use of abstract keyword is optional. Methods in interface is by default abstract.
Inheritance Supported
  • Being a class, an abstract class cannot inherit multiple classes. It can only inherit one class.
  • An Interface can extend (or inherit) multiple interfaces.
What can be extended?
  • An abstract class can extend either normal class or abstract class.
  • Interface can extend only interface but not a class.
Variable type & Access modifier
  • An abstract class can have static, non-static, final or non-final variable with any access modifier.
  • An interface can only have public static final variable. In interface variable is constant.

Example of abstract class

Given below is a simple example of abstract class:

abstract class TutorialsInHand{
      //abstract method- body of the method not defined 
      public abstract void javaTutorial();

      //concrete method or non-abstract method
      public void motive(){
            System.out.print("Provide best learning resources");


Read in detail about abstract method here

Example of Interface

Given below is a simple example of interface in java

interface SampleExample{

   public static final int constVar = 9;

   //abstract method 
   public void method1();


Read in detail about interface in java


Java Interview Questions

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Rohanjit Kumar
Technology geek, loves to write and share knowledge with the world. Having 9+ years of IT experience. B.Tech in Computer Science & Engineering
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