public class Hoved {
    public static void main(String[] args) {
        Person per = new Student("Per", 3);
        per.skrivInfo("aarsenhet");

        Student per2 = (Student) per;
        per2.skrivInfo("aarsenhet");

        int[] arr = new int[10];
        
        Person[] personer = new Person[10];
        Professor leif = new Professor("Leif", "IN1010");
        personer[0] = per;
        personer[1] = leif;

        for(Person p : personer) {
            if(p != null) {
                p.skrivInfo();
            }
        }

        System.out.println(per.toString());
        System.out.println(per2); // equivalent
        
        System.out.println(per.equals(per2));
        System.out.println(per == per2);

        Student s1 = new Student("per", 3);
        Student s2 = new Student("per", 3);
        System.out.println(s1.equals(s2));
        System.out.println(s1 == s2);
    }

    void skrivInfo(Person p) {
        if(p instanceof Student) {
            System.out.println("Jeg er student!");
        } else if(p instanceof Professor) {
            System.out.println("Jeg er professor!");
        }
    }
}

/* 
class Universitet {
    Student per; 

    void skrivInfoOmStudenter() {
        per.skrivInfo();
    }
}
*/

/* 
class Object {
    public String toString();

    public boolean equals(Object o);
}
*/