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2017/2018

POO - Programação Orientada por Objetos OOP - Object-oriented programming

José Valente de Oliveirajvo@ualg.pt

www.ualg.pt | w3.ualg.pt/~jvo/poo

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A welcome in Java programming language

class X {public static void main(String [] a) {

System.out.print(”Welcome\n"); }

} #include <stdio.h> int main(void) {

printf(”Welcome\n"); return 0;

}

jvo@ualg.pt José Valente de Oliveira 4-4

Classes and objectsn A class can be seen as a description of a set

of objects sharing the same data structure(not the same data) and the same behaviour(functions)

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What’s an object?

n An object represents a concrete entity of the problem domain, that handles a specific task

n Examples include:q Tangible things as cars, bank accountsq Roles as employee, boss, ...q Interactions as contract, sale, ...

n An object is like a black box: Internal details are hidden.

jvo@ualg.pt José Valente de Oliveira 4-6

What’s an object?n An object can be seen as an abstraction

which represents an entity with interest forthe problem to solve.

n An object has:q Stateq Behaviourq Identity

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jvo@ualg.pt José Valente de Oliveira 4-7

What’s an object?n An object can be seen as an abstraction

which represents an entity with interest forthe problem to solve.

n An object has:q Stateq Behaviourq Identity

Point A is an object with:

-State: Coordinates (XA=1, YA=1)

- Behaviour: computes the distance between itself and another point

- Identify: Object point A is different from any other object

jvo@ualg.pt José Valente de Oliveira 4-8

Examples of classes and their objects

Class Objects Data Typical functions

Point (0, 0)(4.5; 7.2)

x=0; y =0x=4,5; y=7.2

dist

BankAccount account1 Balance=0Number=12

Transferwithdraw

Fraction ½ Numerator = 1Denominator =2

sum

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OOP Basics

n Identifying objects and assigning responsibilities to these objects.

n Objects communicate with other objects by sending messages.

n Build complex objects based on simple ones

n Three basic ideas:

Procedural vs. Object-Orientedn Procedural

Focus on procedures: credit, debit, compute interest

n Object Oriented

Focus on entities with a well-defined role in the problem domain:Customer, Account

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Procedural vs. Object-Oriented

Why should we care about OOP?

n Modularity - large software projects can besplitted into independent, self-containedmodules.

n Reusability - Programs can be assembledfrom pre-written software components.

n Extensibility - New software components canbe written or developed from existing ones.

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Course main topics

n Elementary concepts of OOP

n Introduction to Object Oriented Modelling and UML (Unified Modelling Language)

n Principles, concepts and techniques of OOP

n Object Oriented Programming using Java

n Elementary data structures

n Fundamental Design Patterns

Learning outcomesn Understand Object Oriented programming

principles and techniques

n Application modelling using UML

n Be familiar with fundamental Design Patterns

n Use Java as a programming language

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From: http://www.tiobe.com/

TIOBE Programming Community Index for September 2017

From: http://www.tiobe.com

Long term trends of Tiobe indices as of September 2017

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From: http://www.payscale.com

Median salary by years of experience

Bibliographyn [Main textbook]

Bruce Eckel, Thinking in Java, 4th edition, Prentice Hall, New Jersey, cf. http://mindview.net/Books/TIJ4

n [Supplementary readings on UML]UML Quick Ref. www.uml.org

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Bibliography

n [Supplementary readings on Design patterns]Erich Gamma, Richard Helm, Ralph

Johnson, John Vlissides, Design Pattern – Elements of Reusable Object-Oriented Software, Addison-Wesley, 1995

[Supplementary readings on Data Structures]Robert Sedgewick. “Algorithms in Java,

3rd edition – parts 1-4: Fundamentals, data structures, sorting, searching”, Addison-Wesley, 2003

Assessmentn Final grade (any season) =

60% final written exam + 40% Lab assignments

n Approval if final grade >= 9.5 (round offs are only applicable to the final grade)

n Admission to final exams: all registered students with i) lab assessment grade >= 7,5 (any season)ii) lab presences >= 2/3

n Final written exam is partially open book, i.e., 25 A4 student prepared pages can be used as consulting material

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Lab assessment

n Lab assessent equals the weighted sum of lab assignments

n Lab assignments are made in working groups of 2 or 3 elements.

n However, the assegment is individual, and depends of the student preformance during the assignment defence.

n Groups registration (for both assignments and classes) is mandatory and should be made at:

www.deei.fct.ualg.pt/POO/Entregas

Labsn Some assignments (i.e.,tutorials) consist only in submitting source code to

Mooshak

n Other assignments (i.e., problems) requires both the submission of source code and a report

n Submissions beyond the deadline will reduce global lab assessment (0.25v per day)

n Criteria for assessment of the assignments: - Correction features that exceed specifications will not be

considered for assessment- Efficiency use of resources: CPU, RAM, etc. - Code reusability - Readability including comments to document the code

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To take away todayn What’s OOP?n Goals for this coursen Main covered topicsn Recommend bibliographyn Assessmentn OOP web resourses