Evolution of interface in Java

Prerequisite : Interfaces in Java
In Java SE 7 or earlier versions, an interface can have only:

Constant variables
Abstract methods

We can’t provide implementations of methods in interfaces.

public interface GFG{ 
      String a = "Geeksforgeeks is the best."; 
      
      void hello(String a); 
      void world(int x); 
} 

Java SE 8:
We can write method implementations in Interface from Java SE 8 and on-wards. We need to use “default” keyword to define them as shown below.
In Java SE 8 and later versions, an interface can have only four kinds of things:

Constant variables
Abstract methods
Default methods
Static methods

public interface GFG{ 
      String b = "Shubham is a brilliant coder."; 
    
      default void hello(String a){ 
         System.out.println("Hello"); 
      } 
      static void world(int x){ 
         System.out.println("World"); 
      } 
      void bye(); 
   } 

Java SE 9:
In Java SE 9 and on-wards, we can write private methods in Interfaces using ‘private’ access modifier as shown below (like other private methods).
In Java SE 9 and later versions, an interface can have:

Constant variables
Abstract methods
Default methods
Static methods
Private methods
Private Static methods

public interface GFG{ 
      String b = "Shubham is a brilliant coder."; 
    
      default void hello(String a){ 
         System.out.println("Hello"); 
      } 
      static void world(int x){ 
         System.out.println("World"); 
      } 
      void bye(); 
  
      private void great(long v){ 
           
      } 
   } 

This article is contributed by Shubham Juneja. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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