Java application EmployeePayrollSystem error PayrollSystemTest.java:56

import java.util.Scanner;

// PayrollSystemTest.java
// Employee hierarchy test program.

public class PayrollSystemTest {
	private static final int BONUS_MONTH = 11;

	public static void main(String args[]) {
		// create scanner object to get values from user
		Scanner input = new Scanner(System.in);

		System.out.println("Employees process polymorphically:\n");

		SalariedEmployee salariedEmployee = getSalariedEmployeeObject(input);
		HourlyEmployee hourlyEmployee = getHourlyEmployeeObject(input);
		CommissionEmployee commissionEmployee = getCommissionEmployeeObject(input);
		BasePlusCommissionEmployee basePlusCommissionEmployee = getBasePlusCommissionEmployeeObject(input);

		System.out.println("Employees processed individually:\n");

		System.out.printf("%s\n%s: $%,.2f\n\n", salariedEmployee, "earned", salariedEmployee.earnings());
		System.out.printf("%s\n%s: $%,.2f\n\n", hourlyEmployee, "earned", hourlyEmployee.earnings());
		System.out.printf("%s\n%s: $%,.2f\n\n", commissionEmployee, "earned", commissionEmployee.earnings());
		System.out.printf("%s\n%s: $%,.2f\n\n", basePlusCommissionEmployee, "earned",
				basePlusCommissionEmployee.earnings());

		// create four-element Employee array
		Employee employees[] = new Employee[4];

		// initialize array with Employees
		employees[0] = salariedEmployee;
		employees[1] = hourlyEmployee;
		employees[2] = commissionEmployee;
		employees[3] = basePlusCommissionEmployee;

		System.out.println("Employees processed polymorphically:\n");

		// generically process each element in array employees
		double earnings = 0;
		for (Employee currentEmployee : employees) {
			System.out.println(currentEmployee); // invokes toString

			// determine whether element is a BasePlusCommissionEmployee
			if (currentEmployee instanceof BasePlusCommissionEmployee) {
				// downcast Employee reference to
				// BasePlusCommissionEmployee reference
				BasePlusCommissionEmployee employee = (BasePlusCommissionEmployee) currentEmployee;

				double oldBaseSalary = employee.getBaseSalary();
				employee.setBaseSalary(1.10 * oldBaseSalary);
				System.out.printf("new base salary with 10%% increase is: $%,.2f\n", employee.getBaseSalary());
			} // end if
				// Add $100 bonus if birth month is November while calculating
				// monthly salary
			if (currentEmployee.getBirthDate().getMonth() == BONUS_MONTH) {
				earnings = (currentEmployee.earnings() * 4) + 100;
			} else {
				earnings = currentEmployee.earnings() * 4;
			}
			// Print monthly salary
			System.out.printf("earned $%,.2f\n\n", earnings);
		} // end for

		// get type name of each object in employees array
		for (int j = 0; j < employees.length; j++)
			System.out.printf("Employee %d is a %s\n", j, employees[j].getClass().getName());
	} // end main

	private static SalariedEmployee getSalariedEmployeeObject(Scanner input) {
		System.out.println("Please enter first name.");
		String firstName = input.next();
		System.out.println("Please enter last name.");
		String lastName = input.next();
		System.out.println("Please enter SSN.");
		String ssn = input.next();
		System.out.println("Please enter Month of Birth.");
		int month = input.nextInt();
		System.out.println("Please enter Day of Birth.");
		int day = input.nextInt();
		System.out.println("Please enter Year of Birth.");
		int year = input.nextInt();
		System.out.println("Please enter Salary.");
		double salary = input.nextDouble();
		// create subclass objects
		SalariedEmployee salariedEmployee = new SalariedEmployee(firstName, lastName, ssn, month, day, year, salary);
		return salariedEmployee;
	}

	private static HourlyEmployee getHourlyEmployeeObject(Scanner input) {
		System.out.println("\nHourly Employee Details");
		System.out.println("Please enter first name.");
		String firstName = input.next();
		System.out.println("Please enter last name.");
		String lastName = input.next();
		System.out.println("Please enter SSN.");
		String ssn = input.next();
		System.out.println("Please enter Month of Birth.");
		int month = input.nextInt();
		System.out.println("Please enter Day of Birth.");
		int day = input.nextInt();
		System.out.println("Please enter Year of Birth.");
		int year = input.nextInt();
		System.out.println("Please enter hourly wages.");
		double hourlyWages = input.nextDouble();
		System.out.println("Please enter hours worked.");
		double hoursWorked = input.nextDouble();
		HourlyEmployee hourlyEmployee = new HourlyEmployee(firstName, lastName, ssn, month, day, year, hourlyWages,
				hoursWorked);
		return hourlyEmployee;
	}

	private static CommissionEmployee getCommissionEmployeeObject(Scanner input) {
		System.out.println("\nCommission Employee Details");
		System.out.println("Please enter first name.");
		String firstName = input.next();
		System.out.println("Please enter last name.");
		String lastName = input.next();
		System.out.println("Please enter SSN.");
		String ssn = input.next();
		System.out.println("Please enter Month of Birth.");
		int month = input.nextInt();
		System.out.println("Please enter Day of Birth.");
		int day = input.nextInt();
		System.out.println("Please enter Year of Birth.");
		int year = input.nextInt();
		System.out.println("Please enter gross sales.");
		double grossSales = input.nextDouble();
		System.out.println("Please enter commission rate.");
		double commissionRate = input.nextDouble();
		CommissionEmployee commissionEmployee = new CommissionEmployee(firstName, lastName, ssn, month, day, year,
				grossSales, commissionRate);
		return commissionEmployee;
	}

	private static BasePlusCommissionEmployee getBasePlusCommissionEmployeeObject(Scanner input) {
		System.out.println("\nBase Plus Commission Employee Details");
		System.out.println("Please enter first name.");
		String firstName = input.next();
		System.out.println("Please enter last name.");
		String lastName = input.next();
		System.out.println("Please enter SSN.");
		String ssn = input.next();
		System.out.println("Please enter Month of Birth.");
		int month = input.nextInt();
		System.out.println("Please enter Day of Birth.");
		int day = input.nextInt();
		System.out.println("Please enter Year of Birth.");
		int year = input.nextInt();
		System.out.println("Please enter gross sales.");
		double grossSales = input.nextDouble();
		System.out.println("Please enter commission rate.");
		double commissionRate = input.nextDouble();
		System.out.println("Please enter base salary.");
		double baseSalary = input.nextDouble();
		BasePlusCommissionEmployee basePlusCommissionEmployee = new BasePlusCommissionEmployee(firstName, lastName,
				ssn, month, day, year, grossSales, commissionRate, baseSalary);
		return basePlusCommissionEmployee;
	}
} // end class PayrollSystemTest