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  1. OO programming and UML Design Dr. Zhen Jiang West Chester University E-mail: zjiang@wcupa.edu

  2. Outline • Introduction to object and class • Introduction to UML • Introduction to UML design

  3. Introduction to object and class • What’s object • Identity • State • Behavior • Sequence Diagram • Statechart Diagram • Messages and methods • What’s class • Objects and Classes • Class Attributes • Operation (Method) • Interfaces • Interfaces and Implementation

  4. What’s object • Fundamentals of Object-Oriented Programming

  5. What’s object • Conceptually, there are many ways to think of an object • something that can be seen or touched • a thing to which some action is directed • something that performs an action • The structure and behaviour of similar objects are defined in their common class • Objects have three properties: identity , state, and behaviour

  6. Object Property 1: Identity • Identity is that property of an object which distinguishes it from all other objects • Most programming languages use variable names to refer to objects • Keep in mind, however, that an object may not have a name; Similarly, an object might have multiple names (aliases) • For this reason, there is a subtle distinction made between the concepts of "name" and "identity"

  7. Object Property 2: State • The state of an object encompasses all of the descriptions of the object plus the current values of each of these descriptions

  8. Object Property 3: Behaviour • Behaviour is how an object acts and reacts, in terms of its state changes and message passing • The state of an object represents the cumulative results of its behaviour • In object-oriented programming, a behaviour is invoked by sending a message to an object

  9. Sequence Diagrams • A sequence diagram is an interaction diagram that focuses on the time ordering of messages • A vertical dashed line is used to represent the lifetime of an object (it’s the object’s lifeline) • A focus of control is a tall, thin rectangle that shows the period of time during which an object is performing an action

  10. : Pilot : ATC : Radar requestLdgClearance(r) checkWeather checkRunwayClear(r) clear clearance

  11. Sequence

  12. Statechart Diagram • Captures dynamic behavior (event-oriented) • Purpose • Model object lifecycle • Model reactive objects (user interfaces, devices, etc.)

  13. Example Objects • There are many physical objects we can examine right in this room • each person is an object • any chair is not an object • each light bulb is an object • Any book is not an object • this room itself is an object (full or not)

  14. See if the followings are objects or not: • Desk • Lamp • Person • Log • The Earth • Clock • Machine • Computer • Saving account • Answer: N, Y, Y, N, Y, Y, Y, Y, Y

  15. Messages and Methods • A object executes a method when it sends/receives a message • For example, we can ask/tell a dog to sit by sending him the message "sit" • In object-oriented programming, objects send messages asking/telling others to perform behaviours -- those other objects invoke the method corresponding to the message in order to execute the desired behaviour

  16. What’s class • A class describes the common structure (attributes/state) and behaviour of its instances • For example, • 3.14, 2.71, and 5.5 can be classified as Floats • the following shapes can be classified as Circles

  17. Classes and Objects • An object is called an "instance" of a class • The terms instance and object are interchangeable • Creating an object from a class is often called instantiation • For example, there are many person objects in this room -- each person is an instance of the person class

  18. Classes and objects • How would we describe the state, behaviour, and identity for each of these objects • We have looked at objects and we have seen that objects can be "classified" into classes • As programmers, we work with both classes and objects from those classes • For example, we might write a stack class and create multiple stack objects for use in our program

  19. In a 2D drawing package, circles have a radius, a line thickness, a line colour, and a fill colour • Each individual circle (instance) drawn by the user has its own value for each attribute • The programmer writes a Circle class and the program instantiates a Circle object every time the user draws a Circle a snowman made from 9 Circle instances

  20. Class Attributes • An attribute is a named property of a class that describes the range of values that instances of the property may hold.(Booch,1999) • An attribute has a type that defines the type of its instances. • Only the object itself should be able to change the value of its attributes. • The values of the attributes define the state of the object

  21. Operation (Methods) • An operation is the implementation of a service that can be requested from any object of the class to affect behavior (Booch, 1999) • An operation can be: • Question (does not change the value of the object) • Command (may change the value of the object)

  22. Interfaces • An interface is a collection of operations that are used to specify a service of a class or a component (Booch, 1999) • An interface is a contract of related services and a set of conditions that must be true for the contract to be faithfully executed • Interfaces formalize polymorphism, they allow us to define polymorphism in a declarative way unrelated to implementation

  23. Interface and Implementation • The class interface is its external (public) view • The class implementation is its internal (private) view • It is convenient to think of the interface as describing "what the objects of this class can do" and the implementation as "how the objects of this class do it" • The implementation of a class consists of all the "behind the scenes" operations defined in the interface of the class

  24. Introduction to UML • What’s UML • Goals of UML • Overview • Class diagram • Introduction • Class icon • Class relationship • Constraints • Other diagrams

  25. UML: Unified Modeling Language • The Unified Modeling Language (UML) is an industry-standard language for specifying, visualizing, constructing, and documenting the artifacts of software systems • The UML definition was led by Grady Booch, Ivar Jacobson, and Jim Rumbaugh (all now at Rational Software)

  26. UML simplifies the process of software design, making a "blueprint" for construction In Essence: a tool used through the analysis and design phases of system development for expressing the constructs and relationships of complex systems Target Usage: for building object-oriented and component-based systems

  27. Goals of UML 1. Provide users with a ready-to-use, expressive visual modeling language so they can develop and exchange meaningful models 2. Provide extensibility and specialization mechanisms to extend the core concepts. 3. Be independent of particular programming languages and development processes. 4. Provide a formal basis for understanding the modeling language. 5. Encourage the growth of the Object-Oriented tools market. 6. Support higher-level development concepts such as collaborations, frameworks, patterns and components. 7. Integrate best practices.

  28. Many free learning materials on the web • e.g. www.rational.com/uml • Standard of UML www.cs.wcupa.edu/~zjiang/01-09-67.pdf • Some recommended texts on UML: • The Unified Modeling Language User Guide, [G. Booch, J. Rumbaugh, I. Jacobson, 2000] • UML Explained, [Kendall Scott, 2001] • Applying UML and Patterns 2nd Ed., [Craig Larman, 2002] • UML Distilled 2nd Ed., [Martin Fowler with K. Scott, 2000] • UML and C++, [R. Lee & W. Tepfenhart, 2001]

  29. UML Overview • UML is a language for visualizing, specifying, constructing and documenting the artifacts of a software system • The artifacts might include requirements, architecture, design, source code, project plans, tests, prototypes, releases

  30. Review something Object action action state1 state2 operations/methods attributes: {attribute1, attribute2} structure operation/method attribute1 attribute2 value

  31. Light Turn on/off On Off operations/methods: Turn_on/off ( ) attributes: {True, False} structure Turn_on True False Turn_off value

  32. Class Diagram • Introduction • Class Icon • Relationships • Constraints

  33. Introduction • The class diagram is fundamental to object-oriented programming • UML’s class diagrams capture the attributes and operations of each class as well the relationships that exist between classes

  34. Class Icon • Class Icon • Hiding Details • Visibility Notation • Attribute Specification • Operation Specification

  35. Class Icon • The UML class icon is a rectangle with three compartments: • class name • class attributes • class operations • Attributes are specified in the following form: • object:class name

  36. Hiding Detail • You can optionally leave out the attributes, operations, or both in a class icon:

  37. UML Member Visibility Notation • UML has three visibility prefixes for members:+ for public, # for protected, and – for private • e.g.

  38. Full UML Attribute Specification • The full form of a UML attribute is as follows:[visibility] name [multiplicity] [: type] [= initial value] [{property}] • The property choices are changeable, addOnly, and frozen

  39. Full UML Operation Specification • The full form of a UML operation is as follows:[visibility] name [(parameter-list)] [:return-type] [{property}] • The property choices are sequential, concurrent, guarded, and isQuery • The full form of a UML parameter is:[direction] name : type [= default-value] • The direction choices are in, out, and inout

  40. UML Class Relationships • A class relationship is a connection between two (or more) classes • The three most important class relationships are generalizations, associations, and aggregations • UML provides a graphical representation for each of the relationships using a different line type for each relationship

  41. Class Relationships • Generalization • Association • Association Class • Qualified Association • Ternary Association • Aggregation

  42. Generalization • A generalization is a relationship between a general thing (superclass) and a more specific kind of that thing (subclass) • In the UML, generalization requires that objects of the subclass may be used anywhere an object of the superclass appears

  43. Association • An association is a structural relationship that specifies that objects of one thing are connected to objects of another

  44. Association • Associations can be adorned with a name. Teaching

  45. Association • Associations can be adorned with the roles. teacher learner

  46. Association • Associations can be adorned with the multiplicity. 1 4..*

  47. Association Class (relation attributes) • Each object of association class is one instance of relationship (link) in an association. 1..* 4..*

  48. Qualified Association • Qualified association relates two classes and a qualifier. • The qualifier is a special attribute that reduces the effective multiplicity of an association.

  49. Ternary Association • A ternary association is a structural relationship that specifies that objects of one thing are connected to objects of other two’s.