Java ООП композиция arraylist

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Main Class
import java.util.ArrayList;

public class Main {

    public static void main(String[] args) {


        ArrayList<Employee> employeesList = new ArrayList<Employee>();
        Employee n1 = new Employee("soiri", 88753, "09645324");
        Employee n2 = new Employee("sofia", 42455, "09645324");
        Employee n3 = new Employee("bolira", 678312, "09645324");
        Employee n4 = new Employee("kobi", 342423, "09645324");
        Employee n5 = new Employee("kestin", 3434, "09645324");
        Employee n6 = new Employee("madrid", 88753, "09645324");
        Employee n7 = new Employee("rob", 524622, "09645324");
        Employee n8 = new Employee("sosi", 143432523, "09645324");
        Employee n9 = new Employee("coli", 2525141, "09645324");
        Employee n10 = new Employee("ban", 2525252, "09645324");
        employeesList.add(n1);
        employeesList.add(n2);
        employeesList.add(n3);
        employeesList.add(n4);
        employeesList.add(n5);
        employeesList.add(n6);
        employeesList.add(n7);
        employeesList.add(n8);
        employeesList.add(n9);
        employeesList.add(n10);






        Invoice invoice = new Invoice(500,"David",n1);



        ArrayList<DayWorking> workingOfDay = new ArrayList<DayWorking>();
        DayWorking d1 = new DayWorking(n1,n2,n3);
        DayWorking d2 = new DayWorking(n2,n4,n6);
        DayWorking d3 = new DayWorking(n7,n8,n9);
        DayWorking d4 = new DayWorking(n3,n1,n10);
        DayWorking d5 = new DayWorking(n5,n8,n9);
        DayWorking d6 = new DayWorking(n10,n5,n2);
        workingOfDay.add(d1);
        workingOfDay.add(d2);
        workingOfDay.add(d3);
        workingOfDay.add(d4);
        workingOfDay.add(d5);
        workingOfDay.add(d6);



        ArrayList<WorkSchedule> week = new ArrayList<WorkSchedule>();
        WorkSchedule w1 = new WorkSchedule(d1);
        week.add(w1);





        invoice.printDetails();


        w1.printWorking();




        //week.printWorking(); //loop
    }

}


public class Employee {

    private String namePurchaseOrder;
    private int id;
    private String phoneNumber;


    public Employee() {

    }

    public Employee(String namePurchaseOrder, int id, String phoneNumber) {

        this.namePurchaseOrder = namePurchaseOrder;
        this.id = id;
        this.phoneNumber = phoneNumber;
    }

    public String getNamePurchaseOrder() {
        return this.namePurchaseOrder;
    }

    public void setNamePurchaseOrder(String namePurchaseOrder) {
        this.namePurchaseOrder = namePurchaseOrder;
    }

    public int getId() {
        return this.id;
    }

    public void setId(int id) {
        this.id = id;
    }


    public String getPhoneNumber() {
        return this.phoneNumber;
    }


    public void setPhoneNumber(String phoneNumber) {
        this.phoneNumber = phoneNumber;
    }



}

public class Invoice {

        private int price;
        private String clientName;
        private Employee seller;


        public Invoice () {

        }

        public Invoice(int price, String clientName, Employee seller) {
            this.price = price;
            this.clientName = clientName;
            this.seller = seller;
        }

    public int getPrice() {
        return price;
    }

    public void setPrice(int price) {
        this.price = price;
    }

    public String getClientName() {
        return clientName;
    }

    public void setClientName(String clientName) {
        this.clientName = clientName;
    }

    public Employee getSeller() {
        return seller;
    }

    public void setSeller(Employee seller) {
        this.seller = seller;
    }

    public void printDetails() {

        System.out.println("Price: "+ price);
        System.out.println("Client Name: "+ clientName);
        System.out.println("Seller: "+ seller);

    }

}



public class WorkSchedule {

   private DayWorking d1;
   private DayWorking d2;
   private DayWorking d3;
   private DayWorking d4;
   private DayWorking d5;
   private DayWorking d6;

    public WorkSchedule(DayWorking d1) {
        this.d1 = d1;
    }



    public WorkSchedule(DayWorking d1, DayWorking d2, DayWorking d3, DayWorking d4, DayWorking d5, DayWorking d6) {
        this.d1 = d1;
        this.d2 = d2;
        this.d3 = d3;
        this.d4 = d4;
        this.d5 = d5;
        this.d6 = d6;
    }

    public DayWorking getD1() {
        return d1;
    }

    public void setD1(DayWorking d1) {
        this.d1 = d1;
    }

    public DayWorking getD2() {
        return d2;
    }

    public void setD2(DayWorking d2) {
        this.d2 = d2;
    }

    public DayWorking getD3() {
        return d3;
    }

    public void setD3(DayWorking d3) {
        this.d3 = d3;
    }

    public DayWorking getD4() {
        return d4;
    }

    public void setD4(DayWorking d4) {
        this.d4 = d4;
    }

    public DayWorking getD5() {
        return d5;
    }

    public void setD5(DayWorking d5) {
        this.d5 = d5;
    }

    public DayWorking getD6() {
        return d6;
    }

    public void setD6(DayWorking d6) {
        this.d6 = d6;
    }


    public void printWorking() {

        System.out.println("The name of the Working monday: " + d1);
        System.out.println("The name of the Working sunday: " + d2);
        System.out.println("The name of the Working thursday: " + d3);
        System.out.println("The name of the Working tuesday: " + d4);
        System.out.println("The name of the Working wednesday: " + d5);
        System.out.println("The name of the Working saturday: " + d6);

    }


}


public class DayWorking {

    private Employee morning;
    private Employee noon;
    private Employee evening;


    public DayWorking() {

    }


    public DayWorking(Employee morning, Employee noon, Employee evening) {
        this.morning = morning;
        this.noon = noon;
        this.evening = evening;
    }

    public Employee getMorning() {
        return morning;
    }

    public void setMorning(Employee morning) {
        this.morning = morning;
    }

    public Employee getNoon() {
        return noon;
    }

    public void setNoon(Employee noon) {
        this.noon = noon;
    }

    public Employee getEvening() {
        return evening;
    }

    public void setEvening(Employee evening) {
        this.evening = evening;
    }
}

Что я уже пробовал:

Это то, что мне нужно сделать..
На выходе я получаю нулевое значение почему ?
Спасибо за помощь!

Напишите отдел, представляющий счет-фактуру покупки в магазине одежды. Счет - фактура должен содержать следующие поля: - сумма покупки - личность покупателя-объект, представляющий сотрудника, совершившего продажу. Для такого объекта мы напишем отдел с полным названием, удостоверением личности и номером телефона. Затем вы должны написать отдел, который представляет рабочую доску в этом магазине. Каждый день в цехе должны работать три работника, и этот отдел должен описывать, кто будет работать каждый день. Для каждого дня введите класс с рабочей доской, состоящей из массива объектов из этого класса.

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