Mixin in Java 20

Mixins in Java are implemented using interfaces. An interface defining the mixin can be created, and then it can be implemented by other classes as needed. Here's an example:

1. First, define the mixin interface:

public interface Flyable {
  void fly();
}

2. Then, implement the interface in your classes:

public class Bird implements Flyable {
  public void fly() {
    System.out.println("Flying...");
  }
}
public class Plane implements Flyable {

  public void fly() {

    System.out.println("Flying...");

  }

}

3. Now you can use the Flyable interface to add fly behavior to other classes:

public class Superhero implements Flyable {
  private Flyable flyable = new Bird();
 
  public void fly() {
    flyable.fly();
  }
 
  public void setFlyBehavior(Flyable flyable) {
    this.flyable = flyable;
  }
}

In this example, the Superhero class implements the Flyable interface, and it has a flyable object that it delegates to for the actual flying behavior. It defaults to using a Bird for the fly behavior, but it can be changed at runtime by calling the setFlyBehavior method with a different Flyable object.

Mixins in Java are a powerful way to add behavior to classes without requiring them to inherit from a common base class. They are particularly useful when working with third-party libraries or APIs that don't provide the behavior you need out of the box.