How and when to use an abstract class

Question

This is my test program in Java. I want to know how much abstract class is more important here and why we use abstract class for this.

Is it a mandatory or is it bes

Answer 1

Abstract class, as its name suggest is abstract.

Abstract class doesn't talk about the implementation part. In fact, we extend the abstract class to provide the implementation for its abstract methods. It can also have non-abstract methods.

Check here : Use of Abstract Class in Java

EDIT :

Sample Code :

abstract class Shapes {

 int i=1;
 abstract void draw(); 

 // Remember : Non-abstract methods are also allowed 
 void fill() {
     System.out.println("Non abstract method - fill");
 }
}

class Shape1 extends Shapes {

 int i=1;
 void draw(){
 System.out.println("This is Shape 1:"+i);
 }
}

class Shape2 extends Shapes {
    int i=2;
    void draw() {
        System.out.println("This is Shape 2:"+i);
    }
}

class Shape {

public static void main(String args[])
       {
        Shape1 s1 = new Shape1();
        s1.draw();                     // Prints This is Shape 1:1

        Shape2 s2 = new Shape2();
        s2.draw();                     // Prints This is Shape 2:2
       }
  }