Polymorphism question, help needed

[Quinn92]

Not sure how to approach the two tasks i have been given below..can anyone tell me where I am going wrong or give me a pointer or two?


– Modify the supplied payroll system to include private instance variable joinDate in class Employee to represent when they joined the company. Use the java.util.Date for this variable.
– Use a static variable in the Employee class to help automatically assign each new employee a unique (incremental) id number.

// Abstract base class Employee.
import java.util.Date;
public abstract class Employee {

    private String firstName;
    private String lastName;
    public Date birthDate;
    // constructor
    public Employee(String first, String last, Date dateOfBirth) {
        firstName = first;
        lastName = last;
        birthDate = dateOfBirth;
    }

    // get first name
    public String getFirstName() {
        return firstName;
    }

    // get last name
    public String getLastName() {
        return lastName;
    }
    
    public void setBirthDate(Date dateOfBirth)
    {
 		birthDate = dateOfBirth;
    }
  
    public Date getBirthDate()
    {
 	   return birthDate;
    }
    
    
    public String toString() {
        return firstName + ' ' + lastName;// how can add dates to this without creating a type problem?
    }

    public abstract double earnings();
}

import java.util.Date;

// CommissionWorker class derived from Employee

public final class CommissionWorker extends Employee {

    private double salary; // base salary per week
    private double commission; // amount per item sold
    private int quantity; // total items sold for week

    // constructor for class CommissionWorker
    public CommissionWorker(String first, String last, Date dateOfBirth,
            double salary, double commission, int quantity) {
        super(first, last, dateOfBirth); // call superclass constructor
        setSalary(salary);
        setCommission(commission);
        setQuantity(quantity);
    }

    // set CommissionWorker's weekly base salary
    public void setSalary(double weeklySalary) {
        salary = (weeklySalary > 0 ? weeklySalary : 0);
    }

    // set CommissionWorker's commission
    public void setCommission(double itemCommission) {
        commission = (itemCommission > 0 ? itemCommission : 0);
    }

    // set CommissionWorker's quantity sold
    public void setQuantity(int totalSold) {
        quantity = (totalSold > 0 ? totalSold : 0);
    }

    // determine CommissionWorker's earnings
    public double earnings() {
        return salary + commission * quantity;
    }

    // get String representation of CommissionWorker's name
    public String toString() {
        return "Commission worker: " + super.toString();
    }
} // end class CommissionWorker

import java.util.Date;

// Boss class derived from Employee.

public final class Boss extends Employee {

    private double weeklySalary;

    // constructor for class Boss
    public Boss(String first, String last, double salary, Date dateOfBirth) {
        super(first, last, dateOfBirth); // call superclass constructor
        setWeeklySalary(salary);
    }

    // set Boss's salary
    public void setWeeklySalary(double salary) {
        weeklySalary = (salary > 0 ? salary : 0);
    }

    // get Boss's pay
    public double earnings() {
        return weeklySalary;
        
    }

    // get String representation of Boss's name
    public String toString() {
        return "Boss: " + super.toString();
    }
} // end class Boss

// Driver for Employee hierarchy

// Java core packages
import java.text.DecimalFormat;
import java.util.Date;

// Java extension packages
import javax.swing.JOptionPane;

public class Test {

    // test Employee hierarchy
    public static void main(String args[]) {
        Employee employee; // superclass reference
        String output = "";

        Boss boss = new Boss("John", "Smith",800.0,  new Date(8, 7,1979));

        CommissionWorker commissionWorker =
                new CommissionWorker("Sue", "Jones",new Date(8, 7,1979),400.0, 3.0, 150);

        PieceWorker pieceWorker =
                new PieceWorker("Bob", "Lewis",new Date(8, 7,1979),  2.5, 200);

        HourlyWorker hourlyWorker =
                new HourlyWorker("Karen", "Price",new Date(8, 7,1979),  13.75, 40);

        DecimalFormat precision2 = new DecimalFormat("0.00");

// Employee reference to a Boss
        employee = boss;

        output += employee.toString() + " earned $"
                + precision2.format(employee.earnings()) + "\n"
                + boss.toString() + " earned $"
                + precision2.format(boss.earnings()) + "\n";

        // Employee reference to a CommissionWorker
        employee = commissionWorker;

        output += employee.toString() + " earned $"
                + precision2.format(employee.earnings()) + "\n"
                + commissionWorker.toString() + " earned $"
                + precision2.format(
                commissionWorker.earnings()) + "\n";

        // Employee reference to a PieceWorker
        employee = pieceWorker;

        output += employee.toString() + " earned $"
                + precision2.format(employee.earnings()) + "\n"
                + pieceWorker.toString() + " earned $"
                + precision2.format(pieceWorker.earnings()) + "\n";

// Employee reference to an HourlyWorker
        employee = hourlyWorker;

        output += employee.toString() + " earned $"
                + precision2.format(employee.earnings()) + "\n"
                + hourlyWorker.toString() + " earned $"
                + precision2.format(hourlyWorker.earnings()) + "\n";

        JOptionPane.showMessageDialog(null, output,
                "Demonstrating Polymorphism",
                JOptionPane.INFORMATION_MESSAGE);

        System.exit(0);
    }
} // end class Test

import java.util.Date;

// PieceWorker class derived from Employee

public final class PieceWorker extends Employee {

   
	private double wagePerPiece; // wage per piece output
    private int quantity; // output for week

    // constructor for class PieceWorker
    public PieceWorker(String first, String last, Date dateOfBirth,
    		double wage, int numberOfItems) {
        super(first, last, dateOfBirth); // call superclass constructor
        setWage(wage);
        setQuantity(numberOfItems);
    }

    // set PieceWorker's wage
    public void setWage(double wage) {
        wagePerPiece = (wage > 0 ? wage : 0);
    }

    // set number of items output
    public void setQuantity(int numberOfItems) {
        quantity = (numberOfItems > 0 ? numberOfItems : 0);
    }

    // determine PieceWorker's earnings
    public double earnings() {
        return quantity * wagePerPiece;
    }

    public String toString() {
        return "Piece worker: " + super.toString();
    }
}

import java.util.Date;

// Definition of class HourlyWorker

public final class HourlyWorker extends Employee {

    private double wage; // wage per hour
    private double hours; // hours worked for week

    // constructor for class HourlyWorker
    public HourlyWorker(String first, String last, Date dateOfBirth,
            double wagePerHour, double hoursWorked) {
        super(first, last, dateOfBirth); // call superclass constructor
        setWage(wagePerHour);
        setHours(hoursWorked);
    }

    // Set the wage
    public void setWage(double wagePerHour) {
        wage = (wagePerHour > 0 ? wagePerHour : 0);
    }

    // Set the hours worked
    public void setHours(double hoursWorked) {
        hours = (hoursWorked >= 0 && hoursWorked < 168
                ? hoursWorked : 0);
    }

    // Get the HourlyWorker's pay
    public double earnings() {
        return wage * hours;
    }

    public String toString() {
        return "Hourly worker: " + super.toString();
    }
}