Full Code Examples - Applied Java Patterns - page 274

19. public double getTimeRequired(){ return timeRequired; }
20.
21. public void setName(String newName){ name = newName; }
22. public void setOwner(Contact newOwner){ owner = newOwner; }
23. public void setTimeRequired(double newTimeRequired){ timeRequired =
newTimeRequired; }
24.
25. public void addProjectItem(ProjectItem element){
26. if (!projectItems.contains(element)){
27. projectItems.add(element);
28. }
29. }
30.
31. public void removeProjectItem(ProjectItem element){
32. projectItems.remove(element);
33. }
34.
35. public void accept(ProjectVisitor v){
36. v.visitTask(this);
37. }
38. }
The basic interface that defines the Visitor behavior is the ProjectVisitor . It defines a visit method for each
of the project classes.
Example A.122 ProjectVisitor.java
1. public interface ProjectVisitor{
2. public void visitDependentTask(DependentTask p);
3. public void visitDeliverable(Deliverable p);
4. public void visitTask(Task p);
5. public void visitProject(Project p);
6. }
With this framework in place, you can define classes that implement the ProjectVisitor interface and perform
some computation on project items. The class ProjectCostVisitor shows how project cost calculations could
be managed.
Example A.123 ProjectCostVisitor.java
1. public class ProjectCostVisitor implements ProjectVisitor{
2. private double totalCost;
3. private double hourlyRate;
4.
5. public double getHourlyRate(){ return hourlyRate; }
6. public double getTotalCost(){ return totalCost; }
7.
8. public void setHourlyRate(double rate){ hourlyRate = rate; }
9.
10. public void resetTotalCost(){ totalCost = 0.0; }
11.
12. public void visitDependentTask(DependentTask p){
13. double taskCost = p.getTimeRequired() * hourlyRate;
14. taskCost *= p.getDependencyWeightingFactor();
15. totalCost += taskCost;
16. }
17. public void visitDeliverable(Deliverable p){
18. totalCost += p.getMaterialsCost() + p.getProductionCost();
19. }
20. public void visitTask(Task p){
21. totalCost += p.getTimeRequired() * hourlyRate;
22. }
23. public void visitProject(Project p){ }
24. }
All behavior for the calculation, as well as variable storage, is centralized in the Visitor class. To add a new
behavior, you would create a new class that implements ProjectVisitor and redefine the four visit methods.
The Contact interface and ContactImpl class represent the owner for a Task or Deliverable .
Example A.124 Contact.java
1. import java.io.Serializable;