Class(implementing the interface) and interface in same file and accessing the class from a main class in different package

I was going through some design pattern videos on YouTube, however I have a small doubt on some basic Java concept. I tried searching for solution, but was unable to find one. Below is my query.

I have some classes Animal.java, Dog.java, an interface Fly.java which also has a class named CantFly in same file. A main method CheckAnimal.java. Below is the code

Animal.java

package com.classification.pojo;

public class Animal {

    public Fly flyingType;

    public String tryToFly() {
        return flyingType.fly();
    }

    public void setFlyingAbility(Fly newFlyType) {
        flyingType = newFlyType;
    }

}

Dog.java

package com.classification.pojo;

public class Dog extends Animal {
    public Dog() {
        super();
        flyingType = new CantFly();
    }

    public void digHole() {
        System.out.println("I am digging hole!");
    }
}

Fly.java

package com.designpattern.strategy;

public interface Fly {
    String fly();
}

class CantFly implements Fly {

    public String fly() {
        return "Can't fly";
    }
}

class ItFlys implements Fly {
    public String fly() {
        return "I can fly";
    }
}

CheckAnimal.java

package com.designpattern.main;

import com.classification.pojo.Animal;
import com.classification.pojo.Dog;
import com.classification.pojo.Fly;

public class CheckAnimals {

    public static void main(String[] args) {
        Animal doggy = new Dog();
        System.out.println(doggy.tryToFly());
        doggy.setFlyingAbility(new ItFlys());
        System.out.println(doggy.tryToFly());
    }

}

In CheckAnimal.java, for doggy object to invoke setFlyingAbility() method correctly, Animal.java, Dog.java and Fly.java needs to be in same package. If I keep Fly.java in different package, I cannot access CantFly() constructor. I hope I have made my point clear.

- Ishan