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Week 2
Wed, Jan 20

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0.
What are classes?
	fields + methods

What are objects: 
	Class definition + "instance data", or "state", for the fields
	
	Objects are very much like DATABASE RECORDS, 
	except for this public/private stuff.
	
How are objects created? 
	with new() and a "constructor"

Fig 1.6 (4th ed, Page 10)

Data types:
	int, String, classes

How do you tell everything apart? This can be tricky
	_ convention (field names begin with _)?? B&K don't use this
	methods calling other methods

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1. Now go on to the TicketMachine.
Version 1:
	variables: private data
	public/private
	ctor
	getPrice
	getBalance
	insertMoney
	printTicket
	
	Ticketmachine "invariant": balance & total are always updated properly.
	
	Exercises 2.7/2.8: change to "class public Ticketmachine", leave out public entirely
	
	Fields/Ctors/Methods
	
	Note that the ctor does NOT return a value!
	You can write functions that don't return a value by putting "void" there.
	
	Look at fields through the Inspector
	
	Formal v Actual params in ctor
	
	Which variable is which? Figuring out what the fields are
	
	accessors & mutators
	
	
	Make TicketMachine print a serial # on each ticket
		private int serialNum
	Add a method ticketCount()
	
	
	What if we don't put in enough money?
	What if we put in too much?
	What if we insert -100000 cents?
	What if the initial ticket price is negative?
	
	This brings us to if-statements: p 36
		
2. TicketMachine Version 2
==========================

	improved logic to printTicket(): make sure enough money was inserted
	
	class vars v local vars
	_ convention?
	
	Overview of ch 2: 
		fields, ctors, methods (accessor/mutator), parameters, assignment, return, if
	
	review structure of a class:
		fields 		almost always private
		ctors		usually public; no return type
		methods		usually public; must have return type (or "void")
			accessors generally return a value
			mutators may or may not.
			
	At least as far as fields go, an object looks like a DATABASE RECORD.
	ISOM 370 registrants take note:
	
	methods calling other methods

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3. picdemo

	picdemo	(pld's example, not a book example)
		train
		Picture
			meteor
			lawngrow
	

	multiple ctors
		adding extra ctors to circle
		how they appear in bluej
		can one ctor call the other? sort of.
			See commented out this(20,60) (but ignore for now)
			
	
	First look at LOOPS
		meteor
		lawnzip -- oops, this probably isn't what we meant
		lawngrow
		Math.random()
		rain
			randombubbles
		
		Note use of RANDOM here that makes rain easier than lawngrow.


Structure of simple NUMERIC while loop:

	n=0;
	while (n<100) {
	    do stuff
	    do more stuff
	    ...
	    probably depends on n; may not though
	    
	    n=n+1;
	}
	
	used in lawngrow, rain, bubbles, meteor
	
		
		Some TABLES of numbers, using loops
		triangletable

An even simpler form of loop is the FOR-EACH loop, 
where we do something to each element of a list (eg print it).
However, the simplicity is perhaps a touch deceptive.


did not finish all loop examples above; see 03.text