Interfejsy (wprowadzenie i porównanie)

Czym jest interfejs?

Kod: implementacja interfejsu

public class Main {
  // Interface that declares a capability
  static interface Drivable {
    void drive(); // method to implement
  }

  // A class implements the interface
  static class Car implements Drivable {
    public void drive() {
      System.out.println("Car is driving");
    }
  }

  public static void main(String[] args) {
    Drivable d = new Car(); // upcast to interface
    d.drive();              // runs Car's method
  }
}

Interfejsy a klasy abstrakcyjne

Kod: metoda domyślna

public class Main {
  // Interface with a default method (has a body)
  static interface Greeter {
    void greet(String name);
    default void sayBye() { // default provides a reusable tiny implementation
      System.out.println("Bye");
    }
  }

  static class SimpleGreeter implements Greeter {
    public void greet(String name) {
      System.out.println("Hello, " + name);
    }
  }

  public static void main(String[] args) {
    Greeter g = new SimpleGreeter();
    g.greet("Ada");
    g.sayBye(); // default method from the interface
  }
}

Wiele interfejsów

Kod: wiele interfejsów

public class Main {
  static interface Drivable { void drive(); }
  static interface Maintainable { void maintain(); }

  static class ServiceCar implements Drivable, Maintainable {
    public void drive() { System.out.println("ServiceCar driving"); }
    public void maintain() { System.out.println("ServiceCar maintenance"); }
  }

  public static void main(String[] args) {
    ServiceCar s = new ServiceCar();
    s.drive();
    s.maintain();
  }
}

Sprawdzian dotyczący interfejsów

Podsumowanie