AdministrationEmployee.java

public class AdministrationEmployee extends Employee {


    public AdministrationEmployee(String name) {
        super(name, Employee.TEMPORARY, 0, "Administration");
    }

    public double getSalary() {
        return  18000;
    }
}

Employed.java

public interface Employed {

    double getSalary();

}

Employee.java

public abstract class Employee implements Employed {

    public static final int TEMPORARY = 0, TRAINING = 1, INDEFINITE = 2;

    private String name;
    private int contract;

    private int years;
    private String department;

    public Employee(String name, int contract, int years, String department) {

        if (contract != TEMPORARY && contract != TRAINING && contract != INDEFINITE)
            throw new IllegalArgumentException();
        if (years < 0) throw new IllegalArgumentException();
        if (!"Management".equals(department) &&
                !"Engineering".equals(department) &&
                !"Administration".equals(department)) throw new IllegalArgumentException();

        this.name = name;
        this.contract = contract;
        this.years = years;
        this.department = department;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getContract() {
        return contract;
    }

    public void setContract(int contract) {
        this.contract = contract;
    }

    public int getYears() {
        return years;
    }

    public void setYears(int years) {
        this.years = years;
    }

    public String getDepartment() {
        return department;
    }

    public void setDepartment(String department) {
        this.department = department;
    }

    // <name>: <department> department, <type of contract> contract, <years> years in the company, salary of <salary> bitcoins
    @Override
    public String toString() {
        String contractStr;
        if (contract == 0)
            contractStr = "temporary";
        else if (contract == 1) {
            contractStr =  "training";
        } else {
            contractStr = "indefinite";
        }
        return name + ": " + department + " department, " + contractStr + " contract, " +
                years + " years in the company, salary of " + getSalary() + " bitcoins";
    }
}

EngineeringEmployee.java

public class EngineeringEmployee extends Employee {


    public EngineeringEmployee(String name, int contract, int years) {
        super(name, contract, years, "Engineering");
    }

    public double getSalary() {
        double startSalary = 25000;
        double stepPerYear = 2500;
        return startSalary + stepPerYear * getYears();
    }
}

ManagementEmployee.java

public class ManagementEmployee extends Employee {

    public ManagementEmployee(String name, int years) {
        super(name, INDEFINITE, years, "Management");
    }

    public double getSalary() {
        double startSalary = 40000;
        double stepPerYear = 6000;
        return startSalary + stepPerYear * getYears();
    }
}

Staff.java

public class Staff {


    public static void main(String[] args) {
        Employee [] staff = new Employee[6];
        staff[0] = new ManagementEmployee("Bill", 9);
        staff[1] = new EngineeringEmployee("Anna", Employee.INDEFINITE, 9);
        staff[2] = new EngineeringEmployee("John", Employee.INDEFINITE, 5);
        staff[3] = new EngineeringEmployee("Elizabeth", Employee.TRAINING, 3);
        staff[4] = new EngineeringEmployee("Michael", Employee.TRAINING, 2);
        staff[5] = new AdministrationEmployee("Albert");

        double managersSalaryTotal = 0;
        double engineersSalaryTotal = 0;
        double adminsSalaryTotal = 0;
        double acmeTotal = 0;
        for (Employee employee : staff) {
            System.out.println(employee);
            acmeTotal += employee.getSalary();
            if ("Management".equals(employee.getDepartment())) {
                managersSalaryTotal += employee.getSalary();
            }
            if ("Engineering".equals(employee.getDepartment())) {
                engineersSalaryTotal += employee.getSalary();
            }
            if ("Administration".equals(employee.getDepartment())) {
                adminsSalaryTotal += employee.getSalary();
            }
        }
        System.out.println();
        System.out.println("MANAGEMENT TOTAL SALARY: " + managersSalaryTotal + " bitcoins");
        System.out.println("ENGINEERING TOTAL SALARY: " + engineersSalaryTotal + " bitcoins");
        System.out.println("ADMINISTRATION TOTAL SALARY: " + adminsSalaryTotal + " bitcoins");
        System.out.println("ACME TOTAL SALARY: " + acmeTotal + " bitcoins");

    }

}