Employee Payroll Solution in Java

import java.io.*;
import java.util.*;

class Cell
{
   Object data;
   Cell next;

   Cell (Object dat, Cell nxt)
   {
      data = dat;
      next = nxt;
   }
   void setNext(Cell n) { next = n; }
   Cell getNext()       { return next; }
   Object objectOf()    { return data; }
}

class List
{
   Cell head;
   Cell tail;

   List () { head = tail = null; }
   void enqueue (Object obj)
   { 
      if (head == null)
      {
         head = tail = new Cell(obj, null);
         return;
      }
      tail.setNext(new Cell(obj, null));
      tail = tail.getNext();
   }
   Cell getHead() { return head; }
}

class Employee
{
   String name;

   Employee() {}
   Employee (String nm) { name = nm; }
   String getName() { return name; }
   double computePay() { return -1; }          // pure virtual
   void   display () {}
   void   setHours(double hrs) {}
   void   setSales(double sales) {}
}

class EmployeeList extends List
{

   EmployeeList() {}

   void setHours(String name, int hrs)
   {
      for (Cell f = getHead() ; f != null ; f = f.getNext())
      {
         if (((Employee)(f.objectOf())).getName() == name)
         {
            ((Employee)(f.objectOf())).setHours(hrs);
            break;
         }
      }
   }

   void setSales(String name, double sales)
   {
      for (Cell f = getHead() ; f != null ; f = f.getNext())
      {
         if (((Employee)(f.objectOf())).getName() == name)
         {
            ((Employee)(f.objectOf())).setSales(sales);
            break;
         }
      }
   }

   double payroll()
   {
      double total=0;

      for (Cell f = getHead() ; f != null ; f = f.getNext())
         total += ((Employee)(f.objectOf())).computePay();
      return total;
   }

   void display()
   {
      for (Cell f = getHead() ; f != null ; f = f.getNext())
         ((Employee)(f.objectOf())).display();
      System.out.println();
   }
}

class WageEmployee extends Employee
{
   double rate;
   double hours;

   WageEmployee(String nm) { super(nm); }
   WageEmployee(String nm, double r) { super(nm); rate = r; }
   void setRate(double r)    { rate  = r; }
   void setHours(double hrs) { hours = hrs; }
   double getHours()         { return hours; }
   double getRate()          { return rate; }
   double computePay()       { return rate*hours; }
}

class Programmer extends WageEmployee
{
   Programmer (String nm, double w) { super(nm, w); }
   void display()
   {
      System.out.println("Name: "+getName()+
                         "\tHours: "+getHours()+
                         "\tRate: "+getRate());
   }
}

class SalesPerson extends WageEmployee
{
   double commission;
   double SalesMade;

   SalesPerson (String nm, double c) 
   {
      super(nm);
      commission = c;
   }
   void setCommission(double comm) { commission = comm; }
   void setSales(double sales) { SalesMade = sales; }
   double computePay() { return commission*SalesMade; }
   void display()
   {
      System.out.println("Name: "+getName()+
                         "\tCommission: "+commission+
                         "\tSales: "+SalesMade);
   }
}

class Manager extends Employee
{
   double monthlysalary;

   Manager () { super(""); }
   Manager(String nm, double w)  { super(nm); monthlysalary = w; }
   void setSalary(double salary) { monthlysalary = salary; }
   double computePay()           { return monthlysalary; }
   void display()
   {
      System.out.println("Name: "+getName()+
                         "\tMonthly Salary: "+ monthlysalary);
   }
}

public class Wages
{
   public static void main(String argv[])
   {
      EmployeeList emp = new EmployeeList();
      emp.enqueue(new SalesPerson("John", 0.03));
      emp.enqueue(new SalesPerson("Joan", 0.04));
      emp.enqueue(new SalesPerson("Jack", 0.02));
      emp.enqueue(new Manager("Fred", 10000));
      emp.enqueue(new Manager("Frank", 5000));
      emp.enqueue(new Manager("Florence", 3000));
      emp.enqueue(new Programmer("Linda", 7));
      emp.enqueue(new Programmer("Larry", 5));
      emp.enqueue(new Programmer("Lewis", 3));

      emp.setHours("Linda", 35);
      emp.setHours("Larry", 23);
      emp.setHours("Lewis", 3);
      emp.setSales("John", 12000);
      emp.setSales("Joan", 10000);
      emp.setSales("Jack", 5000);
      emp.display();
      System.out.println("Payroll: "+emp.payroll());
   }
}