Fundamentals of Software Development 1Slide 1 Today’s Summary UML class diagrams – –Why classes are important – –UML class diagrams – relationships – –UML class diagrams – details for each class MethodsMethods –Invoking a method –Defining a method Summarized on the next few slides Summarized on the slides after the above summary

Fundamentals of Software Development 1Slide 2 Why classes are important What does an object’s type tell you? – –Answer: How the object operates! What attributes the object has What operations the object can do Fact: The type of an object is simply the name of the class to which the object belongs What can you conclude from the above statements? The class (i.e. type) of an object tells you how the object operates!Answer: The class (i.e. type) of an object tells you how the object operates! Questions?

Fundamentals of Software Development 1Slide 3 Review: UML class diagrams What they areWhat they are –A notation to assist object-oriented design (not just Java) Why use UML?Why use UML? –UML as sketch To figure out a designTo figure out a design To communicate ideas and alternativesTo communicate ideas and alternatives –UML as blueprint To convey the design to the coderTo convey the design to the coder –UML as programming language To generate code automatically from the designTo generate code automatically from the design This is how we (and most people) use UML class diagrams – as a tool to help our thinking

Fundamentals of Software Development 1Slide 4 Review: UML class diagrams – relationships-only Order Line Product Corporate Customer OrderCustomer Personal Customer Employee salesRep is-a (by extending a class) is-a (by implementing an interface) has-a 1means one *means 0 or more 1.. *means 1 or more 0.. 1means 0 or 1 lineItem 1 * * * * Questions?

Fundamentals of Software Development 1Slide 5 UML class diagram with details Together, let’s examine JavaEyes and fill in the details for the EyeBall class in the UML class diagramTogether, let’s examine JavaEyes and fill in the details for the EyeBall class in the UML class diagram What are the attributes? Their types?What are the attributes? Their types? –Any comments needed? What are the operations? Their types?What are the operations? Their types? –Any comments needed? EyeBall eyeBallColor : Color xPosition : int yPosition : int radius : int EyeBall(Color eyeBallColor) draw( Graphics graphics) look(int x, int y) Moves the EyeBall to follow the mouse to the given (x, y) point There are two ways to show an object-type attribute: Draw a HAS-A arrow to it List it in the detailed box Choose the former if you want to emphasize the relationship Sets the EyeBall color to the given color Questions?

Fundamentals of Software Development 1Slide 6 Method invocation versus definition “There is a difference between knowing the path and walking the path.” ~ Morpheus“There is a difference between knowing the path and walking the path.” ~ Morpheus “There is a difference between defining a method and invoking a method.” ~ CSSE Prof.“There is a difference between defining a method and invoking a method.” ~ CSSE Prof.

Fundamentals of Software Development 1Slide 7 Method invocation versus definition To define (write) a method means to write its codeTo define (write) a method means to write its code –The code is a recipe to follow when the method runs –Methods often have parameters – information that comes into the method when it is run To invoke (call, run) a method means to cause the method’s code to runTo invoke (call, run) a method means to cause the method’s code to run –Sending it actual values to substitute for the formal parameters of the method Example (on next slides)Example (on next slides)

Fundamentals of Software Development 1Slide 8 Method invocation versus definition To define (write) a method means to write its codeTo define (write) a method means to write its code To invoke (call, run) a method means to cause the method’s code to runTo invoke (call, run) a method means to cause the method’s code to run Example (on next slide):Example (on next slide): –The NameDropper class in the blue box defines: A field called myName to hold the NameDropper’s name to dropA field called myName to hold the NameDropper’s name to drop A constructor called NameDropper that takes the name to store in the fieldA constructor called NameDropper that takes the name to store in the field A method called transform that takes a phrase to tranformA method called transform that takes a phrase to tranform –The statements in the yellow box cause the NameDropper constructor and transform method to run They each run several times, with different actual arguments substituted for the formal parameters in the NameDropper definitionThey each run several times, with different actual arguments substituted for the formal parameters in the NameDropper definition These statements would themselves appear in some other classThese statements would themselves appear in some other class

Fundamentals of Software Development 1Slide 9 public class NameDropper extends StringTransformer implements StringTransformable { private String myName; public NameDropper(String nameToUse) { this.myName = nameToUse; } public transform(String phrase) { return this.myName + “says ” + phrase; } } NameDropper person1, person2, person3; person1 = new NameDropper(“Calvin”); person2 = new NameDropper(“Hobbes”); person3 = new NameDropper(“lobster”); person1.transform(“you look funny today, Hobbes.”); person2.transform(“you looker even funnier.”); person1.transform(“no, YOU look funnier.”); person3.transorm(“I amd just a lonely lobster.”); Definition of the NameDropper class Invoking the NameDropper constructor and transform method

Fundamentals of Software Development 1Slide 10 What’s Ahead? Before the next session:Before the next session: –Do Homework 6 (no late homework!) Including the reading and the associated online quizIncluding the reading and the associated online quiz –Next session: WordGames - Implementing your own classes!WordGames - Implementing your own classes! Reminder: Find the homework assignment from the Schedule page of the CSSE 120 Angel site angel.rose-hulman.edu Suggestion: Routinely do your homework in F-217 (CSSE lab). A student assistant is there every Sunday through Thursday evening, 7 pm to 9 pm, so you can get immediate answers to any questions you might have.