OOP /EBUSS Teachers: Kasper B. Graversen Uffe Kofod Tutors: Johannes Beyer Christian Stærmose

OOP /EBUSSOOP /EBUSS

Teachers:

•Kasper B. Graversen

•Uffe Kofod

Tutors:

•Johannes Beyer

•Christian Stærmose

Copyright 2001 Kasper B. Graversen

Today’s programToday’s program

• 9-11 General information on the course and introduction to OOP.

• 11-12 lunch• 12-15 Lab exercises (in room 3.17)

– Install & setup editor– Compile a working program– Compile failing programs


Course materialCourse material

• Java Gently, 3rd edition by Judy Bishop

• Various tutorials (found on the course webpage)

• Assignments (found on the course webpage)

• www.it-c.dk/~kbilstedwww.it-c.dk/~kbilsted


Course structure

• 12 sessions (of which this is the first)

• 900-1200 lectures

• 1300-1600 computer lab exercises

• 10 homework assignments of which 8 must

be approved in order to attend the 4 hour

exam.

• Group work solving assignments is

encouraged. Max. group size = 2


Handing-in rulesHanding-in rules

• Deliver within deadline in the course folder

• Only printouts are accepted (and don’t count on the printers are working 10 min. before deadline)

• Clearly state your name (and of your collaborator if any)

• Be honest! If it doesn’t work explain what happens and how you got stuck.

• Remember documentation– UML

– Short tutorial

• Don’t cheat! (don’t copy others work)


Top 10 Ways to Piss off your LecturerTop 10 Ways to Piss off your Lecturer• Don't think, just take notes in lectures/tutorials.

• Don't participate in tutorials.

• Skip lectures or lab exercises and then ask for help.

• Ask "Is this on the exam?".

• Don't explore.

• Don't do the lab exercises.

• Copy someone else's lab exercises.

• Talk in lectures.

• Disrupt lectures with mobile phones/laser pointers & showing up late.

• Cheat on assignments.

by Andrew Taylor


The course in general 1The course in general 1

• Learn how computers work

• Be able to handle and transform a given problem to be suited for computers

• Gain programming skills

• And for the less ambitious: to be able to laugh at scenes in the movie “antitrust” (which otherwise is a good movie.)


The course in general 2The course in general 2

Procedural programming in an object-orientated context

The basic data types used in procedural programming

Levels of abstraction in describing software systems.


The course in general 3

• Learn the basics of programming-> “DOS programs” – Programs with no interaction– Programs with interaction from text window

• Learn OOP and GUI framework -> “Ordinary programs”– Programs with interaction from windows

• Learn network and Servlet framework -> dynamic webpages (i.e. e-shops)


How to study

• Programming is a craft – Can not be mastered through reading (just like

any other craft)• Read a bit

• try at the keyboard

– Practice the fundamentals again and again!


How to group workHow to group work

• Find someone at the same level at you

• Take turns at the keyboard

• Make time for individual “figuring out”

• Use each other: Discuss,there exists several solutions to an assignment.

• You should not just divide up the work

between you!


How to read the book

• The first 2-3 chapters are hard to read since they try cover on many aspects of programming.

• Expect reading them several times.


How computers work 1How computers work 1

• What is the biggest number?

34 91 72• How did you find it?


How computers work 2How computers work 2What is the biggest number now?32343 09889 58342 23987 34763 19854 33487 28458

78343 64398 33487 28458 62983 09847 98377 84399

20934 89348 10298 78329 34029 44392 38733 94283

62837 97230 23094 35783 23829 24089 62983 09847

89402 78239 90012 34940 12984 34098 23829 24089

23849 93404 23489 23048 23847 23498 12984 34098

84359 34833 26784 29384 03984 39484 03984 39484

92734 38733 94283 83743 23984 34842 34029 44392

09889 58342 23987 34763 19854 40338 12984 34098

78343 64398 33487 28458 62983 09847 10298 78329

20934 89348 10298 78329 34029 44392 78239 90012

62837 97232 23094 35783 23829 24089 97232 23094

89402 78239 90012 34940 12984 34098 89348 10298

23849 93404 23489 23048 23847 23498 64398 33487


How computers work 3How computers work 3

• Natural language is ambiguous

• Programming languages are unambiguous– Distinguish between = and ==– Everything has to be “spelled out”


The Java language

• abstract boolean break byte case catchchar class const continue default dodouble else extends final finally float for goto if implements import instanceof

int interface long native new packageprivate protected public return short staticsuper switch synchronized this throw throwstransient try void volatile while ++ -- % == = []

Green = important Yellow = covered Gray = not covered

• Not a lot - but think of it as the alphabet and what

you can do with mere ~26 building blocks


What Java adds to C objects, inheritance, interfaces exceptions garbage collection proper modularization facilities better support for arrays, strings multi-threading rich set of platform-independent APIs introspection/meta-operations

by Andrew Taylor


Procedural Programming

• We say functional programming languages such as Haskell/Prolog are declarative.

• A declarative program defines more what is to be computed rather than how to compute

• i.e. sets up a maze and define movement - the program will then automatically find its way out.


Programs and states

• Programs in procedural programming language such as C, C++, Basic, Pascal or Java give a sequence of operations (actions) to produce result.

• A Java program must defines explicitly how to compute a result.

• We say procedural programming languages such as Java are imperative.

by Andrew Taylor


Imperative programs• A state could be a certain position in the maze.

• The only way to get out of the maze is by developing an algorithm for finding out.

• Algorithm: A precise “recipe” for solving a problem.


State change• Procedural programs work by state-change.

• The state of a program: variables (mutable typed containers)

position (place in code where executing)

external files (input/output file positions)

• The program comprises: declarations - (description of variables: names and types)

statements - (list of operations to be performed)

• State is dynamic; program is static. by Andrew Taylor


Object Oriented Programs 1

• Object Oriented programming is procedural programming encapsulated in objects.

• These objects can be named to represent entities in the problems being solved.

• Reading code describing the solution, one reads words expressing the problem.

• OOP allows descriptions of problems and solutions in “ordinary” language, rather than in a language specific to computer platform or programming language.


Object Oriented Programs 2Object Oriented Programs 2

• Code has, over time, become self-contained and easy to describe.

• Through objects code can be passed around and be reused in various places in the program or in several programs.

• Programs are usually newer written from scratch

• One of the reason why Java is popular is the 1732 classes big library of code ready to be used.

• But reuse requires documentation


Object Oriented Programs 3Object Oriented Programs 3

• Any drawbacks in using this fantastic technology?– Small programs relativly are bigger– Keeping track of objects


The world from an OO perspective

• A car

• A Shop

Wheel Wheel

WheelWheelMotor

Steering mechanism

articles customer

customer

customer

customer

Shop

Bank

Accounting

Body


The world from a OO perspective

Attributes• Attributes describes properties of a class

• Car– color– price– cleanness

• Motor– speed

• Wheel– mm rubber

Wheel Wheel

WheelWheelMotor

Steering mechanism

Bodyspeed

colorprice cleanness


The world from a OO perspective

Methods• Methods declares functionality of a class• Body

– openDoor– closeDoor

• Motor– on/off– speedup– brake

• Steering mechanism– left/right

Wheel Wheel

WheelWheelMotor

Steering mechanism

Bodyspeed

colorprice cleanness

openDoor

openDoor

on/off

left right

speedup

brake


Using UML to sketch

BodypricecolorcleannessopenDoorcloseDoor

Motorspeedonoffspeedupbrake

Steering mechanism

leftright

Wheelrubber

1

4


Grouping classes


How java works

Java source code

Java Byte code

Machine code

Compiler

Virtual machine

ExecutionExecution

Editor

Ultraedit

javac

java

(Foo.java)

(Foo.class)


Writing code

Java source code

Compiler

Editor

ultraedit

javac Failure

•Very picky•“;” at the end of (almost) every line•“a” is different from “A” (case sensitive)•A missing parenthesis, the slightest misspelling etc. gives failure


““Hello world” in Java 1Hello world” in Java 1

• The smallest program in java

class Hello

{

public static void main(String[] args)

{

System.out.print(“Hello world!“);

}

}

• Saved in a file called “Hello.java” (notice the capital H)


““Hello world” in Java 2Hello world” in Java 2

• To translate it to something the computer understands we run the compiler

javac Hello.java

• To run the program we type

java Hello

Documents

OOP /EBUSS Teachers: Kasper B. Graversen Uffe Kofod Tutors: Johannes Beyer Christian Stærmose