Dynamic method dispatch

Dynamic method dispatch is a mechanism in Java where the method to be executed is determined at runtime rather than at compile time. It is also known as runtime polymorphism or late binding.

In Java, dynamic method dispatch is achieved through method overriding, where a subclass provides a specific implementation of a method that is already present in its superclass. When a method is invoked on an object, the JVM determines which version of the method to execute based on the actual type of the object at runtime.

Here's how dynamic method dispatch works:

1. Method Override: Subclasses can override methods defined in their superclass to provide specialized implementations. The subclass method must have the same signature (name and parameters) as the superclass method.

2. Runtime Binding: When a method is called on an object, the JVM determines the appropriate method implementation to execute based on the actual type of the object at runtime.

3. Polymorphic Behavior: Dynamic method dispatch allows for polymorphic behavior, where the same method call can exhibit different behavior depending on the actual type of the object.

Example:

class Animal {

    void makeSound() {

        System.out.println("Animal makes a sound");

    }

}

class Dog extends Animal {

    void makeSound() {

        System.out.println("Dog barks");

    }

}

class Cat extends Animal {

    void makeSound() {

        System.out.println("Cat meows");

    }

}

public class Main {

    public static void main(String[] args) {

        Animal animal1 = new Dog(); // Upcasting

        Animal animal2 = new Cat(); // Upcasting

        animal1.makeSound(); // Calls Dog's makeSound() method

        animal2.makeSound(); // Calls Cat's makeSound() method

    }

}

In this example:

- The `makeSound()` method is overridden in both the `Dog` and `Cat` subclasses.

- When `makeSound()` is called on `animal1` and `animal2`, the JVM dispatches the call to the appropriate subclass method based on the actual type of the object (`Dog` or `Cat`) at runtime.

Dynamic method dispatch enables polymorphic behavior in Java, allowing for flexibility and extensibility in object-oriented programming.