Chapter 8.2 : Extending Abstract Class

We can extend Employee class in normal way as follows:

/* File name : Salary.java */

public class Salary extends Employee

{

   private double salary; //Annual salary

   public Salary(String name, String address, int number, double

      salary)

   {

       super(name, address, number);

       setSalary(salary);

   }

   public void mailCheck()

   {

       System.out.println("Within mailCheck of Salary class ");

       System.out.println("Mailing check to " + getName()

       + " with salary " + salary);

   }

   public double getSalary()

   {

       return salary;

   }

   public void setSalary(double newSalary)

   {

       if(newSalary >= 0.0)

       {

          salary = newSalary;

       }

   }

   public double computePay()

   {

      System.out.println("Computing salary pay for " + getName());

      return salary/52;

   }

}

Here, we cannot instantiate a new Employee, but if we instantiate a new Salary object, the Salary object will inherit the three fields and seven methods from Employee.

/* File name : AbstractDemo.java */

public class AbstractDemo

{

   public static void main(String [] args)

   {

      Salary s = new Salary("Mohd Mohtashim", "Ambehta, UP", 3, 3600.00);

      Employee e = new Salary("John Adams", "Boston, MA", 2, 2400.00);

      System.out.println("Call mailCheck using Salary reference --");

      s.mailCheck();

      System.out.println("\n Call mailCheck using Employee reference--");

      e.mailCheck();

    }

}

This would produce the following result:

Constructing an Employee

Constructing an Employee

Call mailCheck using  Salary reference --

Within mailCheck of Salary class

Mailing check to Mohd Mohtashim with salary 3600.0

Call mailCheck using Employee reference--

Within mailCheck of Salary class

Mailing check to John Adams with salary 2400.