Is it possible to change the implementation of a method in a derived class?

Yes, in Java, it is possible to override a method in a subclass — this is called method overriding. To do this, you declare a method with the same signature in the subclass and provide a new implementation. The method in the superclass should not be declared as final.

Example:

class Animal {
    void sound() {
        System.out.println("Some sound");
    }
}

class Dog extends Animal {
    @Override
    void sound() {
        System.out.println("Bark");
    }
}

In this example, the sound() method is overridden in the Dog class.