How can principles of polymorphism be applied to work with different object types?

Polymorphism allows working with objects of different classes through a common interface or base class, calling methods that are implemented differently in each class. This simplifies the code and increases its flexibility.

Example:

interface Animal {
    void sound();
}

class Dog implements Animal {
    public void sound() {
        System.out.println("Bark");
    }
}

class Cat implements Animal {
    public void sound() {
        System.out.println("Meow");
    }
}

public class Main {
    public static void main(String[] args) {
        Animal a = new Dog();
        a.sound(); // Bark

        a = new Cat();
        a.sound(); // Meow
    }
}

Here, a variable of type Animal can refer to objects of different classes, and the call to the sound() method will be executed according to the actual type of the object.