Classes Student + Teacher Java Exercise - Java Programming Course

package December_19th;
public class Teacher extends Person
{
	private String subject;
	public final void Explain()
	{
		System.out.println("Explanation begins");
	}
}

package December_19th;
import java.util.*;
public class Main
{
	public static void main(String[] args)
	{
		boolean debug = false;

		//Create a Person and make it say hello
		Person myPerson = new Person();
		myPerson.Greet();

		/*Create a student, set his age to 21, 
		  tell him to Greet and display his age*/
		Student myStudent = new Student();
		myStudent.SetAge(21);
		myStudent.Greet();
		myStudent.ShowAge();

		/*Create a teacher, 30 years old, 
		 *ask him to say hello and then explain*/
		Teacher myTeacher = new Teacher();
		myTeacher.SetAge(30);
		myTeacher.Greet();
		myTeacher.Explain();

		if (debug)
		{
			new Scanner(System.in).nextLine();
		}
	}
}

package December_19th;
public class StudentextendsPerson
{
	public final void ShowAge()
	{
		System.out.printf("My age is: %1$s years old" + "\r\n", age);
	}
}

upackage December_19th;
private sing System;
public class Person
{
	protected int age;
	public final void Greet()
	{
		System.out.println("Hello");
	}
	public final void SetAge(int n)
	{
		age = n;
	}
}