Thread: NumberFormat to Java String Format

Help, on a homework assignment my instructor made the following comment, could anybody please help in making this change:

In the Employee's toString, you are using the NumberFormat class to format your hourly rate and weekly pay but you are supposed to use java string formatting only (%f).
You should change those to use only string formatting - no use of NumberFormat.

package coursework;
 
import java.text.NumberFormat;
 
public class Employee {
 
	private String firstName;
	private String lastName;
	private int employeeId;
	private double hourlyRate;
	public Timecard timeCard;
 
	public Employee(String firstNameInput, String lastNameInput, int idInput,
			double rateInput, int[] daysIn) {
		setFirstName(firstNameInput);
		setLastName(lastNameInput);
		setEmployeeID(idInput);
		setHourlyRate(rateInput);
		setTimeCard(new Timecard(daysIn));
	}
 
	public void printEmpDetails() {
		System.out.println("Name: " + firstName + " " + lastName);
		System.out.println("Emp. Id: " + employeeId);
		System.out.println("Hourly Rate: $" + hourlyRate);
		System.out.println();
	}
 
	private void setFirstName(String firstName) {
		// Here we are setting our class variable firstName to the passed in
		// variable "name"
		// But only if it has a length greater than 0 and less than or equal to
		// 20
 
		int nameLength = firstName.length();
 
		if (nameLength < 1) {
			System.out.println("First Name length is too small");
			System.out.println(firstName + ": " + firstName.length());
		} else if (nameLength > 20) {
			System.out.println("First Name length is too long");
			System.out.println(firstName + ": " + firstName.length());
		} else {
			this.firstName = firstName;
		}
	}
 
	private void setLastName(String lastName) {
		// Here we are setting our class variable firstName to the passed in
		// variable "name"
		// But only if it has a length greater than 0 and less than or equal to
		// 20
 
		int nameLength = lastName.length();
 
		if (nameLength < 1) {
			System.out.println("Last Name length is too small");
			System.out.println(firstName + ": " + lastName.length());
		} else if (nameLength > 20) {
			System.out.println("Last Name length is too long");
			System.out.println(firstName + ": " + lastName.length());
		} else {
			this.lastName = lastName;
		}
	}
 
	private void setEmployeeID(int employeeId) {
		// Here we are setting our class variable firstName to the passed in
		// variable "name"
		// But only if it has a length greater than 0 and less than or equal to
		// 20
 
		if (employeeId > 9999) {
			System.out
					.println("Number length error: this should be less than 9999: "
							+ employeeId);
		} else if (employeeId < 1000) {
			System.out
					.println("Number length error: this should be more than 1000: "
							+ employeeId);
		} else {
			this.employeeId = employeeId;
		}
	}
 
	private void setHourlyRate(double hourlyRate) {
		// Here we are setting our class variable firstName to the passed in
		// variable "name"
		// But only if it has a length greater than 0 and less than or equal to
		// 20
 
		if (hourlyRate < 0) {
			System.out
					.println("Incorrect value, number must be greater than zero: "
							+ hourlyRate);
		} else {
			this.hourlyRate = hourlyRate;
		}
	}
 
	public void setTimeCard(Timecard newtimeCard) {
 
		if (newtimeCard == null) {
			System.out.print("time card cannot be null");
			System.exit(-1);
		}
		timeCard = newtimeCard;
	}
 
	public Timecard getTimeCard() {
		return timeCard;
	}
 
	public String getFirstName() {
		// Here we are getting our class variable firstName
		return firstName;
	}
 
	public String getLastName() {
		// Here we are getting our class variable lastName
		return lastName;
	}
 
	public int getEmployeeId() {
		// Here we are getting our class variable firstName
		return employeeId;
	}
 
	public double getHourlyRate() {
		// Here we are getting our class variable firstName
		return hourlyRate;
	}
 
	public double getWeeklyPay() {
		int regHrs = 0;
		int otHrs = 0;
		for (int i = 0; i < 5; i++) {
			int hrsDay = getTimeCard().getHoursByDay(i);
			int ot = 0;
			if (hrsDay > 8) {
				ot = hrsDay - 8;
				hrsDay = hrsDay - ot;
			}
			regHrs += hrsDay;
			otHrs += ot;
		}
		double baseWeeklyPay = (regHrs * getHourlyRate()) + (otHrs * getHourlyRate() * 1.5);
		char begId = String.valueOf(getEmployeeId()).charAt(0);
		if (begId == '0' || begId == '2' || begId == '9') {
			baseWeeklyPay = baseWeeklyPay * 1.1;
		} else if (begId == '3') {
			baseWeeklyPay = baseWeeklyPay * 0.9;
		} else if (begId == '8') {
			baseWeeklyPay = baseWeeklyPay * 1.2;
		}
		if (regHrs > 34) {
			baseWeeklyPay = baseWeeklyPay * 0.94;
		}
		return baseWeeklyPay;
	}
 
	public String toString() {
		StringBuilder sb = new StringBuilder();
		String.format formatter = StringFormat.getCurrencyInstance();
 
		sb.append(String.format("Name:          %s %s",getFirstName(),getLastName())).append("\n")
				.append(String.format("Id:            %s",getEmployeeId())).append("\n")
				.append(String.format("Hourly Rate:   %s",formatter.format(getHourlyRate()))).append("\n")
				.append(getTimeCard());
 
		sb.append(String.format("Weekly Pay :   %s",formatter.format(getWeeklyPay())));
		sb.append("\n");
 
		return sb.toString();
	}
 
}

I have no idea