public class Person
{
    private String name;
    private Date birthday;
    public Person()
    {
        this(“”,new Date(0,0,0));
    }
    public Person(String name, Date birthday)
    {
        this.name=name;
        this.birthday=birthday;
    }
    public String getName()
    {
        return name;
    }
    public String toString()
    {
        return String.format("Name: %s\nBirthDay: %s\n",name,birthday);
    }
}

public class Employee extends Person
{
    private double salary;
    public Employee()
    {
        super();
        salary=0;
    }
    public Employee(String name, Date birthday, double salary)
    {
        super(name,birthday);
        this.salary=salary;
    }
    public double getSalary()
    {
        return salary;
    }
    public String toString()
    {
        return String.format("%sSalary: %.2f Vnd\n",super.toString(),salary);
    }
}

public class Manager extends Employee
{
    private Employee assistant;
    public Manager()
    {
        super();
    }
    public Manager(String name, Date birthday, double salary)
    {
        super(name,birthday,salary);
    }
    public void setAssistant(Employee assistant)
    {
        this.assistant=assistant;
    }
    public String toString()
    {
        return String.format("%sAssistant: %s",super.toString(),assistant);
    }
}

public class Date
{
    private int month; // 1-12
    private int day;   // 1-31 based on month
    private int year;  // any year

    // constructor: call checkMonth to confirm proper value for month;
    // call checkDay to confirm proper value for day
    public Date( int theMonth, int theDay, int theYear )
    {
        month = checkMonth( theMonth ); // validate month
        year = checkYear(theYear); // validate year
        day = checkDay( theDay ); // validate day
    } // end Date constructor

    // utility method to confirm proper month value
    private int checkMonth( int testMonth )
    {
        if ( testMonth > 0 && testMonth <= 12 ) // validate month
        return testMonth;
        else // month is invalid
        {
            System.out.printf(
                "Invalid month (%d) set to 1.", testMonth );
            return 1; // maintain object in consistent state
        } // end else
    } // end method checkMonth

    // utility method to confirm proper day value based on month and year
    private int checkDay( int testDay )
    {
        int daysPerMonth[] =
        { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
        if (year%400==0||(year%4==0&&year%100!=0))
            daysPerMonth[2]=29;
        // check if day in range for month
        if ( testDay > 0 && testDay <= daysPerMonth[ month ] )
            return testDay;

        // check for leap year
        if ( month == 2 && testDay == 29 && ( year % 400 == 0 ||
            ( year % 4 == 0 && year % 100 != 0 ) ) )
            return testDay;

        System.out.printf( "Invalid day (%d) set to 1.", testDay );
        return 1;  // maintain object in consistent state
    } // end method checkDay

    private int checkYear( int testYear )
    {
        if (testYear>=0)
            return testYear;
        System.out.printf( "Invalid Year (%d) set to 0.", testYear );
        return 0;
    }

    public void nextDay()
    {
        int daysPerMonth[] =
        { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
        if (year%400==0||(year%4==0&&year%100!=0))
            daysPerMonth[2]=29;
        if (day==daysPerMonth[month])
        {
            day=1;
            if (month==12)
            {
                month=1;
                year++;
            }
            else
                month++;
        }
        else
            day++;
    }
    // return a String of the form month/day/year
    public String toString()
    {
        return String.format( "%d/%d/%d", month, day, year );
    } // end method toString
} // end class Date

public class PeopleTest
{
    public static void main(String args[])
    {
        // Test Task 1.a
        Employee newbie = new Employee("Newbie", new Date(2,10,1989), 1000000);
        Manager boss = new Manager("Boss", new Date(2,23,1979), 4000000);
        boss.setAssistant(newbie);
        Manager bigBoss = new Manager("Big Boss", new Date(12,3,1969), 10000000);
        bigBoss.setAssistant(boss);
        System.out.println(newbie);
        System.out.println(boss);
        System.out.println(bigBoss);

        // Test Task 1.b
        Person people[] = {newbie,boss,bigBoss};
        for (int i=0;i<3;i++)
        {
            System.out.println(people[i]);
        }
    }
}