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Appendix G: Object-Oriented Programming with Java 6. How is a redefined method introduced into a Java subclass? 7. The Java keyword abstract has two uses. Give examples of each and explain their usage. 8. Answer the following, giving explanations. (a) Can an interface extend another interface? […]

Object-Oriented Design with UML and Java public Rectangle(double upperLeftX, double upperLeftY, double width, double height) { this(new Point(upperLeftX, upperLeftY), width, height); } public double getPerimeter() { return 2 * (theWidth + theHeight); } public double getArea() { return theWidth * theHeight; […]

Appendix G: Object-Oriented Programming with Java Java supports multiple inheritance through interfaces. A class can be an extension of at most one abstract class or concrete class and implement any number of interfaces. The isA relation is still present, but now an instance of the subclass can be substituted for […]

Object-Oriented Design with UML and Java co.hire(e1, m3); co.hire(e2, m3); co.printEmployeeDetails(); } } The UML collaboration diagram of figure G.5 shows the configuration of objects and the message flows between them. The application, represented by the actor, sends the message printEmployeeDetails to the Company object […]

Appendix G: Object-Oriented Programming with Java public void hire(SalesEmployee sales, SalesManager man) { Iterator iter = theEmployees.iterator(); while(iter.hasNext() == true) { Employee emp = (Employee)iter.next(); if(emp instanceof SalesManager && emp == man) { SalesManager manager = (SalesManager)emp; manager.addSalesMember(sales); } } […]

Object-Oriented Design with UML and Java Concrete subclass SalesManager and SalesEmployee must provide an implementation for printDetails. For class SalesManager we first print the details for the manager, then we cycle through the sales team members printing their name. Note also the method addSalesMember for adding a new SalesEmployee object […]

Appendix G: Object-Oriented Programming with Java All staff have a name, job title and salary. A SalesEmployee has a sales target set against them. A SalesManager has a budget and is a manager for any number of the sales employees. -theEmployees 0..* 0..* -theSalesTeam Company […]

Object-Oriented Design with UML and Java The collection is, of course, a mix of Employee and Manager objects. When we select an item from the collection we cast it to some kind of Employee object. The polymorphic effect of the operation printDetails is determined dynamically at run-time according to […]

Appendix G: Object-Oriented Programming with Java Employee Manager Company -theEmployees 0..* Figure G.3 Company/Employee class diagram The one-to-many relationship between a Company object and its Employee objects is realized by an ArrayList object as part of the Company class. The method hire in the […]

Object-Oriented Design with UML and Java Observe how the method printDetails is reintroduced in the subclass Manager. This is an example of method redefinition. The subclass is a more specialized version of the superclass with a budgetary responsibility, and requires a different presentation from this method. Note also how […]