Open-Closed-Principle.java

//A class should be open for extension and closed for modification.
// This one is a bad Example
class AnimalFeeder {
    public void feedDog() {}
    public void feedCat() {}
    public void feedBird() {}
    // ...
}



//This one is a Good one

interface Animal {
    void feed();
}


class AnimalFeeder {
    public void feed(Animal a) {
        a.feed();
    }
}

// now whatever object we want we can simply pass in AnimalFeeder method and we don't need to modify AnimalFeeder class if we want to extend the functionality of Animal

class Dog implements Animal {
    public void feed() {}
}

class Cat implements Animal {
    public void feed() {}
}