public class PersonStudentTest {

	/**
	 * Tests the Person and Student classes
	 */
	public static void main(String[] args) {
		Person p = new Person("Sara", 25);
		p.speak();
		Student s = new Student("Huy", 27, 3.9);
		s.speak();
		
		Person q = s; // type conformance rule
		q.speak(); // calls speak in Student -> dynamic binding
		// Any variable has two types
		// static type: defined when the variable is declared
		// For instance, the static type of q is Person.
		// dynamic type: the type of the object that the variable
		// refers to
		// For q, the dynamic type is Student
		// the static type never changes. The dynamic type may 
		// change.
		
		// Create an array of Person objects (some of the elements
		// may be Student objects)
		Person[] a = new Person[5];
		String[] names = 
			{"Tanya", "Bobby", "Mauricio", "Xiwei", "Polar"};
		for (int i = 0; i < a.length; i ++) {
			int age = (int) (Math.random() * 10) + 20;
			if (Math.random() < 0.5) { // person
				a[i] = new Person(names[i], age);
			} else { // student
				double gpa = 3.5 + 0.5 * Math.random();
				a[i] = new Student(names[i], age, gpa);
			}
		}
		
		// Call speak for each element of a
		for (Person e: a) {
			e.speak();
		}
		
	}

}