class StudentTest 
{
	public static void main(String[] args) 
	{
		Person bob = new Student("Bob", 17, 3.7f);
		Person jane = new Person("Jane", 21);
		//Object arrays can hold anything - well anything that we can refer to.
		Object[] allTheStuff = new Object[10];
		allTheStuff[0] = bob;
		
		//Autoboxing allows for a primitive like an int to be placed into an Object 
		//(in this case, the Integer class) automatically without us saying:
		//allTheStuff[1] = new Integer(7); 
		//These two lines are equivalent, however.
		allTheStuff[1] = 7;

		allTheStuff[2] = jane;

		//Auto-unboxing occurs as well, thanks to the cast to int. 
		//This is equivalent to the code:
		// int x = ((Integer)allTheStuff[1]).intValue();
		int x = (int)allTheStuff[1];

		//Displays 7
		System.out.println(x);

		//Calls toString on the Student, even though its compile-time type was Person
		System.out.println(allTheStuff[0]);
		//Calls toString on the Person
		System.out.println(allTheStuff[2]);
	}
}

class Student extends Person
{
	private float qpa;

	public Student(String name, int age, float qpa) {
		super(name, age);
		this.qpa = qpa;
	}

	//Overrides Person's toString to be more specific to a Student.
	public String toString() {
		//we invoke the superclass toString method (from Person) as part of it
		return super.toString() + ", QPA: " + qpa;
	}

	public float getQPA() {
		return qpa;
	}

	public void setQPA(float qpa) {
		this.qpa = qpa;
	}
}

class Person //implicitly extends Object
{
	private int age;
	private String name;

	public Person(String name, int age) {
		this.name = name;
		this.age = age;
	}

	//No-arg constructor - we have to make this if we want to create someone with
	// new Person(). If we don't, and we want to force them to use a parameterized
	// constructor, just omit this constructor.
	public Person() { }

	public int getAge() {
		return age;
	}
	
	public String getName() {
		return name;
	}

	
	public void setAge(int age) {
		this.age = age;
	}
	
	public void setName(String name) {
		this.name = name;
	}

	//Overrides Object's toString method
	public String toString() {
		return "Name: " + name + ", Age: " + age ;
	}
}