//pickup your quiz, midterm leftover, etc

//I'll post some sample questions for exam soon

//recall the Student class and its 2 subclasses:

Student s = new Student("Pam", 8923423);
s.toString()

StudentAthlete s1 = new StudentAthlete("Joe", 98023423, "Swimming")
s1.toString()
s1.getSport()

StudentNerd s2 = new StudentNerd("Joe", 98023423, 25);
s2.toString()
s2.getSprot() //ooops! s2 is a StudentNerd, it has no knowlege of StudentAthlete class
s2.readBook()
s2.toString()

s1.readBook() //oops!  s1 is a StudentAthlete , it has no knowlege of StudentNerd class

s.readBook() //oops! what's the problem?
s.getSport() //oops! what's the problem?

//here is the class hierarchy:
                 Object
                   |
               Student
                   |
                 /   \
     StudentAthlete   StudentNerd

Student s3
s3 = s1  //remember s1 (athelte) is a student
s3.toString()
s3.getSprot()

s3 = s2   //remember s2 (nerd) is a student
s3.toString()
s3.readBook()

StudnetNerd s4
s4 = s1 //oops! s1 is athlete which is not nerd so cannot assign!!

StudnetNerd s5
s5 = s2 //oops! s2 nerd is which is not athlete so cannot assign!!

//How do we know what object s refers to? we use isntanceof operator:
s1 instanceof Object
s1 instanceof Student
s1 instanceof StudentAthlete
s2 instanceof Object
s2 instanceof Student
s2 instanceof StudentAthlete


Student s = s2 //recall s2 is athlete
// apparent type of s is Student
// real type of s is StudentAthlete
//you can cast it back to StudentAthlete to access the extra methods:
StudentAthlete s6 = (StudentAthlete) s;
s6.getSport()

Student s = new Student("David", 8783274);
StudentAthlete s4 = (StudentAthlete) s; //oops!!

// Can't cast a Student to type StudentAthlete.  There are
// more methods/data in StudentAthlete than there are in Student.
// We can cast a StudentAthlete to type Student.  We just ignore
// the additional data/methods.

//also we cannot cast a StudentNerd into StudentAthlete!


Student[] a = new Student[3]
a[0] = new Student("s1",1000)
a[1] = new StudentAthlete("s2",2000,"Swimming")
a[2] = new StudentNerd("s3",3000,8)

a[i].toString()
a[i].getSport()!!

//let's write OO class, to see what compiles and what doesn't