- announcements
  - exam conflicts
  - CodeLab 1 due today @ 11:58 pm
  - reading: Ch 1, Ch 2.1-2.3
  - online survey
  - CodeWarrior Tutorial due Monday
  - CodeLab 2 due Wednesday 9/15
  - Assignment 0 posted online (due Friday 9/17)
  - Office Hours room change to CSS 1306

- 11:00 last week catchup

  - how parts of computer work as pertinent to Java
  - programs stored in storage device
    - secondary
    - nonvolatile
    - slow
  - when run, bring program into main memory
    - primary/volatile/fast
    - prefixes are binary
      - k = 2^10 = 1,024
      - M = 2^20 = 1,048,576
      - G = 2^30 = 1,073,741,824
    - Stack, heap
    - static, constant
  - CPU does actual work
  - may use communication device (modem, cable, DSL)

  - Programming Lang
    - categories
      - machine
      - assembly (assembler)
      - high-level
        - OO
      - compilers
      - Java bytecode, VM and interpreter
    - errors
      - compile-time
      - run-time
      - logical
    - Why not Engligh

  - Java
    - James Gosling, Sun
    - C based
    - web programming: applets (mini-app for browser)
    - applications
    - clean design

  - Demo program

/* 
 * Demo of a program.
 * No one should be deprived of a "Hello world" program!
 */
public class HelloWorld {
       public static void main(String[] args) {

              System.out.println("Hello World!");
              }

}

11:10 OBJECTS AND CLASSES
  OBJECT DEFINITION
  OBJECT UML
  CLASS DEFINITION
  CLASS UML
  DISTINCTION: SOPHIE'S WORLD

     ____________
    |            |
    | <obj name> |
    | ---------- |
    |____________|

    ______________
   |              |
   | <class name> |
   |              |
   |              |
   |______________|

- object: thing we can imagine
  - data
  - ops that manipulate data
- programs: interacting objects
- notation: UML = Unified Modeling Language
- mulitple objs of same type in program
- program has instr to create objs
- class: obj definition
  - what objs can and cannot do
- obj: instance of exactly one class
  - obj "belongs to" class
- no lim on # instances of a class
- class versus object: Sophie's World

11:20 MESSAGES AND METHODS
  MESSAGE: TO OBJ FROM OUTSIDE
  METHOD: INTERNAL IMPL OF MESSAGE
  UML
  ARGUMENTS
  RETURN VALUES
  INSTANCE VS CLASS

                     ____________
                    |            |
<msg name>(<args>)  | <obj name> |
------------------->| ---------- |
       <|---o       |____________|
     <return val>


- programming:
  1) define classes
  2) use classes & objs to accomplish tasks
- message
  - instruct class/obj to perform task
  - message UML:
- must program class/obj to process msg
  - method: instructions to perform a task
    - class: defined for class  } more
    - instance: defined for obj } below
  - argument: value passed to obj in association w/ msg
  - msg name sent must match some method def
- instance methods: pertain to individual instance/obj
  - one-way msg
    - obj performs msg op
    - obj does not communicate back to msg sender
  - two-way msg: obj returns information to sender
    - can be data
    can be success/fail status
- class methods: pertain to all instances of a class
  - deal w/ collective info about all instances of a class

11:30 CLASS AND INSTANCE DATA
  DATA
  DATA AND MESSAGES
  CLASS VS INSTANCE
  MEMBER/VALUE
  TYPES: VARIABLE VS CONSTANT
    ______________
   |              |
   |  <obj name>  |
   |  ----------  |
   |______________|
   |              |
   |  <var name>  |
   |  {frozen}    |
   |  __________  |
   | |          | |
   | | <varval> | |
   | |__________| |
   |______________|

    ______________
   |              |
   | <class name> |
   |______________|
   |              |
   |  <var name>  |
   |  ----------  |
   |  {frozen}    |
   |  __________  |
   | |          | |
   | | <varval> | |
   | |__________| |
   |______________|

- class & instance data values
  - store information about self
  - often altered by messages
- all instances of same class
  - possess same set of data values
  - content may vary
- class data value
  - information shared by all instances
  - collective information about the instances
  - an instance can access data vals of the class to which it belongs
- data member synonym for data val
- representing class data val as instance data val wastes space
- types of data vals
  - variable: can change over time
  - constant
    - cannot change over time
    - keyword frozen on UML diagrams
- data val summary
  - class var
  - class const
  - instance var
  - instance const

11:40 INHERITANCE
  DEFINITION
  SUPERCLASS/ANCESTOR/BASE CLASS
  SUBCLASS/DESCENDANT/DERIVED CLASS
  HIERARCHY
  POWERFUL
   ___
  |   |
  |___|
    ^
    |
   ___
  |   |
  |___|

- inheritance
  - use to design 2+ entities that are different but share many common features
    1) superclass/ancestor/base class
       - class w/ common features
       - cannot refer to items defined in subclass
    2) subclass/descendant/derived class
       - extension of common class
       - inherits all attributes of common class
       - can refer to items defined in superclass
- hierarchy
  - subclass is superclass of other classes
- powerful: develop complex programs efficiently and elegantly

11:45 SOFTWARE ENGINEERING/LIFE CYCLE
- computer programming
  - writing code
  - software development
- good developer
  - know lang
  - know how to design program
    - here: OO
- software engineering
  - systematic, disciplined
  - development, testing, maintenance
- software life cycle
  - conception --> operation
  - phases
    - analysis
      - needs of customer
      - feasibility
        - yes --> requirements specification
                  - testable
    - design
      - specification --> design
      - OO: set of classes
    - coding
      - design --> program
      - here: Java program
      - easier than design
    - testing
      - run program
      - varying data sets
      - types (OO)
        - unit: classes individually
        - integration: classes working together
      - debugging: eliminating errors (design and coding)
    - operation
      - use program
      - maintenance
        - make changes
        - additional features
        - undetected errors
        - 70% software cost