Question on Abstraction

Question

What is the difference between the following snippets of code:

abstract class Animal{
abstract void makeSound();
}
class Cat extends Animal{
public void makeSound(){
System.out.println("Meow! Meow!");
}
}
public class MyProgram{
public static void main(String[] args){
Animal cat = new Cat();
cat.makeSound();
}
}

and

class Cat{
public void makeSound(){
System.out.println("Meow! Meow!");
}
}
public class MyProgram{
public static void main(String[] args){
Cat cat = new Cat();
cat.makeSound();
}
}

They both print "Meow! Meow!" but the upper one is an abstraction. What is the value of having an abstraction in this case?

Answer 1

Abstraction is necessary as the abstract classes may not be instantiated, and require subclasses to provide implementations for the abstract methods.

That's very handy for me! :-D