Comp 170, Week 4 (Week of Feb 02)


pld Notebook
lab-classes
picdemo.Numerics

exam 1 is Feb 18, up through the end of chapter 4.

============================================================	
============================================================

   for:each loop versus while loop:
	
	int totallen = 0;		// in the file
	for(String note : notes) {
		totallen += note.length();
	}
	
    While loop:
	int totallen = 0;
	int n = 0;
	while (n<notes.size()) {
		String note = notes.get(n);
		totallen += note.length();
		n++;
	}
	
   Classic "for" loop:
   
	int totallen = 0;
	for (int n = 0; n < notes.size(); n++) {
		String note = notes.get(n);
		totallen += note.length();
	}

 
Overview of notebook.pld

	listReverse
		cannot use for:each loop

	totallength
		straightforward loop

	searchNotes
		uses note.contains(s)
		may have multiple hits; can't return anything

	findFirst
		returns the first one found

	longestNote
		note need to record the note that is longest
		do shortestNote()? 
		
	relation to min date (year or year/month)

==================================================================


lab-classes example

searchStudent(String theID): returns true or false, 
*not* the Student object corresponding to that id.

Why?

Note how this is implemented, and how we could change it.
If we wanted the Student object returned, if found,
we probably would return null if not found.

Also note that we're NOT really going through the entire list
of students, even though it looks like we are: we stop, 
and *return*, when the first match is found.


enrollStudent(): now uses searchStudent()

	if (searchStudent(newStudent.getStudentID())) {
	    System.out.println("Student with ID " + newStudent.getStudentID() + " already enrolled");
	    return;
	} else {


============================================================
============================================================
Wednesday

Ctor in Membership: nobody asked about "throws IllegalArgumentException"!
That's probably a good thing, in that this "weird stuff" didn't confuse too much.


emphasize EVERYTHING IS DEFINED SOMEWHERE

==================================================================


project picdemo, class Numerics
several numeric loops

	numtable(): table of cubes, classic-for loop
	triangletable():
		table of rows, classic-for loop
	sumNums():
		while loop
	triangleRow:
		classic-for loop
		rewrite as while
	
	isPrime()
		while loop; done before
	
	primeTable(): 
		while loop

Numeric examples with max

	find max of 130x - x^2 for 1<=x<=100

	repeatedly calculate rand.nextInt(100) until we reach 0
	
	Count the # of iterations (length), and count the max
	
	Do it 1000 times and find max length
	
===================================================
============================================================

club:
	joinedInMonth(int month): Exercise 4.24, p 112
	deleteMember(String memToDelete)
		note that this chokes ONLY on the last member!

============================================================
=================================================

   Iterator loop:
   	p 95
   	iterator loop to find the total length of all the notes:

   	Iterator<String> it = notes.iterator();
   	while(it.hasNext()) {
   		totallen += it.next().length();
   	}

MailServer iterator loop: 
Use iterator (or while) because we can remove an item from the list
being processed.

    public MailItem getNextMailItem1(String who)
    {
        Iterator<MailItem> it = items.iterator();
        while(it.hasNext()) {
            MailItem item = it.next();
            if(item.getTo().equals(who)) {
                it.remove();
                return item;
            }
        }
        return null;
    }

=================================================


loop patterns:
	processing a list
	processing a range of numbers 1..N
	processing N times
	
	printing or other repeated action
	sum
	search
	max

================================================================

Monday's lab: Kakutani/Collatz sequences

	Start with an integer N > 1.

	if N is odd, let N = 3*N+1
	if N is even, let N = N/2

	keep going.

	7, 22, 11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1

	Do you ever reach 1? (apparently so, though it's not proven)
	If so, how long does it take? 
	What is the largest N reached on the way?