Part 1: Introduction. Course Contents. Books. Goals. Sources for Slides (Acknowledgements) Webpage. The course web page is at

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1 1 Course Contents 2 Part 1: Introduction Difference between conventional and objectoriented programming Introduction to object-oriented programming with Java lots of Java details aimed at producing and maintaining medium sized software systems. Goals 3 Books 4 Sound knowledge of programming principles Sound knowledge of object-orientation Able to critically assess the quality of small and medium software systems Able to implement a medium-sized software systems in Java Java How to program Deitel & Deitel, Prentice Hall Objects First with Java A Practical Introduction using BlueJ David J. Barnes & Michael Kölling, Pearson Education, 2003 ISBN Object-Oriented Software Construction Bertrand Meyer (Pearson 1997), ISBN Sources for Slides (Acknowledgements) 5 Webpage 6 David J. Barnes & Michael Kölling Sigi Benkner, University of Vienna, Inst. f. Software Science Donald Bell, California State Polytechnic University, Pomona Deitel & Deitel, Prentice Hall T. Fahringer, Inst. of Computer Science, UIBK The course web page is at dps.uibk.ac.at/~tf/lehre/ss04/seii/vorlesung.html There is also a mailing list for this course. Please check them regularly. They will be used for announcements and distribution of material.

2 Course overview (1) 7 Software Engineering 8 Introduction to Computer Introduction to Java Applications Introduction to Java Applets Control Structures Arrays Object Oriented Programming Inheritance Polymorphism Exception Handling and much more Software Engineering should help to reach similar quality levels for large software systems as achieved for classical engineering disciplines. Goals: cost-effective software development high quality meet all time constraints Example: Erroneous Software 22. Juli 1962, Cape Canaveral/Florida: Start of the 1st US Venus satellite Mariner 1. Excerpt of a Fortran program to control the carrier rocket Atlas-Agena B (NASA):... IF (TVAL. LT. 0.2E-2) GOTO 40 DO 40 M = 1, 3 WO = (M-1) *0,5... DO 5 K = 1. 3 T (K) = WO Z = 1.0/(X**2) *B1** E-4*BO**2 D (K) = 3.076E-2*2.0*(1.0/X*BO*B E-4(BO**2-X*BO**2-X*BO*B1))/Z E (K) = H**2* *WO/SIN (WO)*Z H = D (K) E (K) 5 CONTINUE 10 CONTINUE Y = H/WO-1 40 CONTINUE 9 Definition: Software Engineering F.L. Bauer (NATO Konferenz, 1968) The establishment and use of sound engineering principles in order to obtain economically software that is reliable and works efficently on real machines. Standard Glossar IEEE (1983)... Is the systematic approach to the development, operation, maintenance, and retirement of software. 10 Main Task of Software Development 11 Software 12 Development The term software comprises a set of artifacts: programs documents data Quality Assurance Maintenance Management Software products are developed for a certain customer (custom software) or for the general market (generic software).

3 Costs and Complexity of Software 13 Traditional Software Development 14 COST EFFORT LINES OF Products (US million) (Man Year) CODE Lotus V Space Shuttle CitiBank Teller Waterfall model Dominated software development for a long time Widely applied through many different variations Requirement Analysis Design Implementation Test Maintenance A paramount problem of software development is the handling of complexity. Trend towards more and more complex software: Distributed applications (Internet, Grid, Mobile Computing,...) Multimedia Real time applications Main problems: Strict classification of software projects Discrete transition among phases Late discovery of design errors (late design breakage) Late appearance of actual code Risk not to meet requirements Impedance mismatches Impedance mismatches 15 Traditional Software Development (1) 16 Structured Analysis and Design (SA/SD) As Management requested it. As the Project Leader defined it. As Systems designed it. Basis are analysis techniques developed between 1965 u Center: Modeling of processes through functions. Widely applied (conventional software development) Main focus: Implementation and Test Complex maintenance Aufwand As Programming developed it. As Operations installed it. What the user wanted. (Pre-1970 cartoon; origin unknown) Requirement Analysis Design Implementation Test Traditional Software Development (2) Software Errors during Design and Implementation 17 Costs of Error Correction % of errors found before release x Coding 36% 64% Analyse/Design 1, 5-6 x 1 x Defintion Development After release 30% of errors found before release

4 Object-Oriented Software Development At the end of the 80s a change of paradigm in software engineering occurred: object orientation Object-oriented Analysis and Design (OOA/OOD) Based on OO technology (starting in 1985) Object models are central (union of data and process models) centric: analysis and design Simplified maintenance Aufwand 19 Object-oriented versus Procedural Object-oriented Paradigm Data and Operations (Methods) define unit Class Center issue: What Smalltalk, C++, Java,... In contrast: procedural programming Separation of data and methods (procedures) Center issue: How Pascal, C, Fortran, Requirement Analysis Design Implementation Test OOA/OOD versus SA/SD 21 Introduction to Objects 22 Library Information System Object-Oriented A/D Structured A/D Catalog Book Librarian Library OOA/OOD Classification based on concepts (objects) Record Loans System Add Resources Report Fines SA/SD Classification based on processes (functions) What are Objects? To a child they are something perceptible by one or more of the senses. To an IT professional they are a software packets that abstract important features of a real object. Porsche

5 25 26 Los Angeles Alan Kay (Customer) Versateller 1. Things Porsche 2. Places Los Angeles 3. Roles Alan Kay 4. Systems Versateller Real objects have characteristics: 29 Real objects also have behaviors: Porsches Top Speed 2. Los Angeles Population 3. Customers d Owed 4. Versatellers Amount on Hand 1. Porsches Accelerate 2. Los Angeles Tax 3. Customers Purchase 4. Versatellers Dispense Cash

6 31 32 Objekts have characteristics and behavior Porsche Top Speed, Accelerate Los Angeles Population, Tax Alan Kay Amount Owed, Purchase Versateller Amount on Hand, Dispense Cash Key 1 Key2 Key 3 A software object has both characteristics (variables) and behavior (methods) encapsulated in it. Software objects communicate by messages. Software objects can inherit characteristics and behavior just like many real objects. Key one: Characteristics are encapsulated by the objects behavior Greeting 33 Key two: Objects communicate by messages 34 Bank Location Call Bank Call Bank Location Dispense Money $100 Key two (also): Messages are polymorphic (mean different things to different objects) 35 Key three: Objects can be classified into classes 36 triangle.redraw() ellipse.redraw() rectangle.redraw() Classes are a template that is used to manufacture objects (instances) (Note that instance is a synonym of object) Polymorphism means different implementations can be hidden behind a common interface.

7 Key three (also): Classes contain the behavior called methods while the instances contain the characteristics called variables Interest Withdraw 37 Key three (also): Each class can inherit both variables and methods ACCOUNT Account# Open Deposit 38 SAVINGS Minimum Withdrawal CHECKING Service Charge Check Key three (also): 39 Object 40 Methods and variables can override their parents (CD Deposit overrides Account Deposit) ACCOUNT Account# Open Deposit A software packet that abstracts the salient behavior and characteristics of a real object into a software package that simulates the real object. CD Rate Due Date Renew Deposit SAVINGS Minimum Withdrawal CHECKING Service Charge Check Encapsulation Message The containment of the data behind a software membrane consisting of methods. The data can only be accessed through the encapsulated behavior. A signal from a client object requesting services from a server object. The message may contain arguments. The server object may return a response.

8 Class 43 Instance 44 A template for defining new object instances. It is sometimes called an object class. The methods reside in the object class. A term used to refer to an actual object. Sometimes called an object instance. Inheritance A technique to allow classes to use a parent classes methods and data. Inheritance can have many levels 45 Polymorphism A request handling mechanism that selects a method depending on the message and the target object. Thus the message means different things to different objects. 46 Overriding 47 Method 48 Where an overloaded method is chosen from the child class instead of from the parent class. The actual computer code that is encapsulated in the object class.

9 49 Summary 50 Subclass A class that has a parent class to inherit from. Object technology is the current modern paradigm OO can enable reuse of system design and coding effort (and consequently save a lot of time and money) Systems built with object technology should be able to be built faster, be more reliable, and be more maintainable Use of object technology requires a different way of thinking than does traditional programming