We have to calculate the percentage of marks obtained in three subjects (each out of 100) by student A and in four subjects (each out of 100) by student B. Create an abstract class 'Marks' with an abstract method 'getPercentage'. It is inherited by two other classes 'A' and 'B' each having a method with the same name which returns the percentage of the students. The constructor of student A takes the marks in three subjects as its parameters and the marks in four subjects as its parameters for student B. Create an object for eac of the two classes and print the percentage of marks for both the students.

abstract class Mark  //Creating an Abstract class{

abstract double getPercentage();}

class A extends Mark{

double result;

A( int val1, int val2, int val3){

 result=(val1+val2+val3)/3;}

double getPercentage(){

 return result;}}

class B extends Mark{

double result;

B(int val1, int val2, int val3, int val4){

 result=(val1+val2+val3+val4)/4;}

double getPercentage(){

 return result;}}

class Main{

public static void main(String args[]){

 //class A Object

 Mark obj_1=new A(10,20,30);

 System.out.println(obj_1.getPercentage());

 //class B Object

 Mark obj_2=new B(10,20,38,46);

 System.out.println(obj_2.getPercentage());}}

so much for the extra points :