关于java中任意对象强制转换为接口类型的问题

public class Apple implements Eatable{
    public static void main(String args[]) {
        Drinkable drinkable = (Drinkable)new Apple();
    }
}
interface Eatable{}
interface Drinkable{}

public class Apple extends Eatable{
    public static void main(String args[]) {
        Drinkable drinkable = (Drinkable)new Apple();  报错 inconvertible types: can not cast Apple to Drinkable
    }
}
class Eatable{}
class Drinkable{}