public class Employee {
    private final int employeeID;
    private final String lastName;
    private final String[] firstNames;
    private final double hourlyRate;
    
    // Note: This code assumes InvalidEmployeeException
    // is in the same package as this source code.
    public Employee(final int id, final double hourlyRate,
        final String[] firstNames, final String lastName)
        throws InvalidEmployeeException {

        // set employeeID
        if (id <= 0) throw new InvalidEmployeeException("ID less than 1");
        this.employeeID = id;
        // set hourlyRate
        if (hourlyRate < 0.0) throw new InvalidEmployeeException("Employee rate less than 0");
        this.hourlyRate = hourlyRate;
        // set firstNames
        if (firstNames == null) this.firstNames = new String[0];
        else this.firstNames = (String[])firstNames.clone();
        // set lastName
        if (lastName == null) throw new InvalidEmployeeException("Last name is missing");
        else this.lastName = lastName;
    }

    public Employee(final int id, final double hourlyRate,
        final String firstName1, final String firstName2,
        final String lastName) throws InvalidEmployeeException {
        this(id, hourlyRate, new String[]{firstName1, firstName2}, lastName);
    }

    public Employee(final int id, final double hourlyRate,
        final String firstName, final String lastName)
        throws InvalidEmployeeException {
        this(id, hourlyRate, new String[]{firstName}, lastName);
    }

    public Employee(final int id, final double hourlyRate,
        final String lastName) throws InvalidEmployeeException {
        this(id, hourlyRate, new String[0], lastName);
    }
    public int getID() { return employeeID; }
    public double getHourlyRate() { return hourlyRate; }
    public String getFirstName(final int pos) {
        if (pos >= firstNames.length) return null;
        else return firstNames[pos];
    }
    public String getLastName() { return lastName; }
    public int getNumberOfFirstNames() { return firstNames.length; }
    public String toString() {
        String result = "Employee: #" + employeeID + ", Name: ";
        for (String s : firstNames) result = result + s + " ";
        result += lastName + " (Rate: "
            + String.format("$%.2f", hourlyRate) + ")";
        return result;
    }
}