Interfaces - language feature

Example from 1 languages: Java

interface MyInterface{
   /* This is a default method so we need not
    * to implement this method in the implementation
    * classes
    */
   default void newMethod(){
       System.out.println("Newly added default method");
   }
   /* Already existing public and abstract method
    * We must need to implement this method in
    * implementation classes.
    */
   void existingMethod(String str);
}
public class Example implements MyInterface{
  // implementing abstract method
    public void existingMethod(String str){
        System.out.println("String is: "+str);
    }
    public static void main(String[] args) {
      Example obj = new Example();
      
      //calling the default method of interface
        obj.newMethod();
        //calling the abstract method of interface
        obj.existingMethod("Java 8 is easy to learn");
  
    }
}

Example from 1 languages: TypeScript

// https://www.typescriptlang.org/docs/handbook/interfaces.html
interface SquareConfig {
   color?: string;
   width?: number;
}

Example from 1 languages: Swift

protocol MyProtocol {
init(parameter: Int)
var myVariable: Int { get set }
var myReadOnlyProperty: Int { get }
func myMethod()
func myMethodWithBody()
}
extension MyProtocol {
func myMethodWithBody() {
  // implementation goes here
  }
}

Example from 1 languages: Kotlin

interface Named {
   val name: String
}
interface Person : Named {
    val firstName: String
    val lastName: String
    
    override val name: String get() = "$firstName $lastName"
}

Example from 1 languages: Objective-C

@protocol Printing
   -(void) print;
@end

Example from 1 languages: GraphQL

interface Character {
 id: ID!
 name: String!
 friends: [Character]
 appearsIn: [Episode]!
}
type Human implements Character {
  id: ID!
  name: String!
  friends: [Character]
  appearsIn: [Episode]!
  starships: [Starship]
  totalCredits: Int
}
type Droid implements Character {
  id: ID!
  name: String!
  friends: [Character]
  appearsIn: [Episode]!
  primaryFunction: String
}

Languages with Interfaces include Java, TypeScript, Swift, Kotlin, Objective-C, GraphQL

Languages without Interfaces include progsbase

View all concepts with or missing a hasInterfaces measurement

Read more about Interfaces on the web: 1.