package types.casting;

interface Animal { default public String f () { return "Animal"; } }
interface Fish extends Animal { default public String f () { return "Fish"; } }
interface Bird extends Animal { default public String f () { return "Bird"; } }
class Cod implements Fish { public String f () { return "Cod"; } }
class Owl implements Bird { public String f () { return "Owl"; } }

public class Main {
  private Main() {}
  public static void main(String[] args) {
    Cod cod = new Cod ();
    Owl owl = new Owl ();
    
    /* Implicit upcasts always compile and run ok */
    Animal aCod = cod;
    Animal aOwl = owl;
    
    /* Explicit upcast  causes an unnecessary cast warning */
    //Animal aCod2 = (Animal) cod;

    /* Explicit downcasts always compile, but may cause runtime errors */
    //Fish f1 = aCod;        // implicit downcast: compiler error
    //Fish f2 = (Fish) aOwl; // explicit downcast: runtime error
    Fish f3 = (Fish) aCod;   // explicit downcast: runtime success

    /* Crosscasting to a class is disallowed by the compiler */
    //Cod f4 = (Cod) owl;          // crosscast: compiler error
    
    /* Crosscast can be replaced by upcast+downcast */
    //Cod f5 = (Cod) (Animal) owl; // upcast+downcast: runtime error

    /* Crosscasting to an interface is allowed by the compiler */
    //Fish f6 = (Fish) owl;        // crosscast: runtime error
    
    /* Casting changes the declared type, but not the actual type */
    System.out.println("Animal: " + aCod.f());
    System.out.println("Fish:   " + f3.f());
    System.out.println("Cod:    " + cod.f());
  }
}