Why to use abstract???

Question

/*abstract class Animal {
int legs = 0;
abstract void makeSound();
}*/

class Cat /*extends Animal*/ {
public void makeSound() {
System.out.println("Meow");
}
}

public class Program {
public static void main(String[] args) {
Cat c = new Cat();
c.makeSound();
}
}

Answer 1

The abstract oblige you to make the develop the fucntion makeSound() in any class who implement Animal. It's a way to be sure that all the animal (class cat, dog, fish) have the same function (makeSound).

Answer 2

Object abstraction allows for a kind of a blueprint of a given class of objects. So, in this case, the abstract class animal allows for the blueprint of any given animal, so you can implement a cat that will have animal characteristics.