LECTURE NOTES
1 DECEMBER 2004

ASSIGNMENTS
6:00 PM Assignment 5 Design
Fri 12/3 CodeLab #12
Wed 12/15 Assignment 5 Code

ASSIGNMENT 4 DISCUSSION

- grading questions?
- BufferedReader connected to System.in
  - no reason to ever have more than one of these
  - can declare a single one to be shared by your whole program
  - can cause correctness problems
- limited capacity: ArrayList
- looping:
  - no loop
  - calls to the start() / main() method
- references to objects are shared: applicability to arrays
- testing strings for equality: equals() versus ==
- accessing a character in a string: charAt (vs. StringTokenizer)
- StringTokenizer - initialize with delimiter
- prompt for second argument: 
  v(iew), a(dd), t (frequency), d(elete), c(har per word)
- words can be any kind of ASCII character: includes caps and numbers
- errors are logical, not necessarily compile:
  - nothing wrong (to readLine) if user enters v a
  - that is a command line error
- be precise when following the specs: lots of failed testcases b/c error 
  messages didn't match exactly
- incremental development
- concept questions?

ABSTRACT, CONT'D

Exercise:
Premise?
- assume 3 classes: B and C inherit from A
  - makes sense to have kinds of A other than B or C
Design?
- make A instantiable
  - add default behavior to A
  - A is no longer abstract
- define another child of A, D
  - A remains abstract
- which one is better varies with the situation: 
  which makes it easier to do modifications?

INHERITANCE V. INTERFACE

What?
- OO features to model is-a relationships
  - inheritance
  - interface

What?
- intended use of interface
  - share common behavior (method headers) among instances of different classes
  - one class can implement multiple interfaces

What?
- intended use of inheritance
  - share common code among the instances of related classes
  - a single subclass can extend at most one superclass
  - superclasses include data members and/or methods that are shared by the 
    subclasses
  - unlike interface, is a specialization relationship

ASSIGNMENT 5 DISCUSSION

- what are "things" in a game of computer checkers?
- what are "actions"?
- how do these actions relate to these things?

# Under what conditions will the game be over?
# How do you check that a human player clicked on a piece?
# How do you determine whether a move is invalid?
# How do you determine whether a human player may select a piece?
# Will a human player be able to deselect a piece if they change their mind?
# What happens if the human player selects an invalid move?
# How will inheritance be incorporated in your design?
# How will you draw the board?

- what should we use to model a 2D board of squares?
- what do we do to enforce the rules?

- classes
  - need at least 3, up to 5 to do correctly
  - brainstorm what classes necessary
  - using inheritance is a requirement! (there is a good way to use it)
  - rules portion (Checkers) contains
    - graphical portion (CheckerBoard)
      - why? 
        - what if wanted to play checkers by displaying to stdout?
        - could reuse rules portion!
  - Piece
    - can I be moved?
      - needs to know what the rest of the board looks like
      - how do we have two objects refer to each other?
  - RegularPiece and King are similar but different... this makes me think of?
    - inheritance
    - which of the two strategies discussed above seems most appropriate?