Why is it important to use polymorphism in Java?

Polymorphism in Java allows objects of different classes to be processed through a single interface or base class. This is important because:

• It increases flexibility and extensibility of the code — new classes can be added without modifying existing code.
• It simplifies maintenance and testing, as the code works with abstractions rather than specific implementations.
• It enables the use of dynamic method invocation (runtime polymorphism), making the program's behavior more adaptable.

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
    }
}