CMPUT 301: Lecture 04 Practical OO constructs & UML Lecturer: Martin Jagersand Department of Computing Science University of Alberta Notes based on previous courses by Ken Wong, Eleni Stroulia Zach Dodds, Martin Jagersand

2 Goals today: 1.Introducing UML 2.Some more basic OO examples in Java Note: Many examples taken from: Dennis Kafura “Object oriented software design and construction” On-line version of book:

3 UML Unified Modeling Language Class notationObject Notation

4 GUI Window

5 UML class example public class Frame { // version 1 … public Frame ( String name, int initXCoord, int initYCoord, int initWidth, int initHeight ) { … } public void resize( int newHeight, int newWidth ) { … } public void moveTo( int newXCoord, int newYCoord ) { … } public void drawText( String text, int atX, int atY ) { … } … } Java

6 UML Object Notation

7 Named Constants public class Frame { … public static final int MOUSE_DOWN = 1; public static final int MOUSE_UP = 2; public static final int MOUSE_DRAG = 3; public static final int MOUSE_MOVE = 4; … } if (eventType == Frame.MOUSE_DOWN) { … }

8 UML Constant Notation Public class-level attributes in the Frame class: +MOUSE_DOWN: Integer = 1; {invariant} +MOUSE_UP: Integer = 2; {invariant} +MOUSE_DRAG: Integer = 3; {invariant} +MOUSE_MOVE: Integer = 4; {invariant}

9 Overloaded Methods Overloaded methods are a set of methods (of a class) that have the same name (and same conceptual action) but different argument lists.

10 Overloaded Methods public class Frame { … // constructors overloaded to provide defaults public Frame( String name, int initXCoord, int initYCoord ); public Frame( String name ); public Frame(); … // methods overloaded for different inputs public void resize( int newHeight, int newWidth ); public void resize( float factor ); … }

11 UML Class Notation

12 Interacting Objects An object can be passed around, representing a bundle of related information. The information exchange occurs between a sender object and receiver object.

13 Interacting Objects To pass information from a sender object to a receiver object: –parameter passing –return value

14 Parameter Passing public class Sender { … public void callerMethod() { Receiver receiver = new Receiver(); Info argRef = new Info(); … receiver.calledMethod( argRef ); … } } public class Receiver { … public void calledMethod( Info infoRef ) { // do something with passed Info object … } }

15 Return Value public class Receiver { … public void callerMethod() { Sender sender = new Sender(); Info infoRef = sender.calledMethod(); // do something with returned Info object … } } public class Sender { … public Info calledMethod() { Info resultRef = new Info(); … // return a reference to an Info object return resultRef; } }

16 Call By Value In Java, there is essentially only call by value. A primitive value (e.g., int, char, etc.) is copied when passed. An object has its reference copied when passed; the object itself is not copied. Strings and arrays are passed like objects.

17 Call By Value public class Sender { … public void callerMethod() { Receiver receiver = new Receiver(); Info argRef = new Info(); … receiver.calledMethod( argRef ); argRef.doSomeMore(); } } public class Receiver { … public void calledMethod( Info infoRef ) { infoRef.doSomething(); infoRef = null; } }

18 Collaborating Objects A group of interacting objects can form: –associations (or acquaintances) –aggregations (or containments)

19 Collaborating Objects Each object has a role in the group and collaborates with (i.e., uses, connects to, knows about) other objects to perform its role.

20 Collaborating Objects Connections between objects: –client/server (unidirectional) –client object invokes methods of server object –client object knows about the server object –peer (bidirectional) –peers know about each other and use each others’ methods

21 Sequences of Interactions A controlling object might perform a sequence of operations over a set of objects.

22 UML Sequence Diagram

23 UML Sequence Diagram Participating objects. Time flows down. Method invocations. Iteration and conditionals. Activation of objects. Creation of objects. Optional return arrows. Notes. Not to scale.

24 Sequence Displaying an image: –ask user for filename of image –create image using contents of given file –draw image in a Frame

25 Sequence Classes of participating objects: –ImageTest (implements Program interface) –FileChooser (asks for filename) –Image (create image from file) –Frame (draw image)

26 UML Sequence diagram

27 Assignment 1 You are to design and implement a simple image viewer that allows the user to: – load and view an image – view the image size – rescale the size of the image – adjust the brightness of the image See detailed specification on the course www page

28 Study (unix/linux) image editor: xv

29 Mathematical / Computational image models Continuous mathematical: I = f(x,y) Discrete (in computer) addressable 2D array: I = matrix(i,j) Discrete (in file) e.g. ascii or binary sequence:

30 Image representation for display True color, RGB, …. (R,G,B) (R,G,B) … (R,G,B) : (R,G,B)

31 Image representation for display Indexed image (I) (I) … (I) : (I) (R,G,B) : (R,G,B)

32 Point operations on images Point operations perform some operation on one pixel at a time (independent on the neighboring pixels) For each ( x,y ) I 2 ( x,y ) = f(I( x,y )) Contrast to image transforms (later in course) perform operations on the whole image

33 Common point operations Brightness adjustment Contrast adjustment –Dynamic range compression –Gray level slicing Histogram equalization Image (sequence) averaging Background subtraction

34 Linear brightness and contrast adjustment As seen on TV! Brightness For each ( x,y ) I 2 ( x,y ) = I( x,y )+const Contrast I 2 ( x,y ) = const*I( x,y )

35 Contrast adjustment example