Code Refactoring 17
In this part of the code refactoring tutorial I will answer another challenge I recently received. This tutorial is all about the Visitor Design Pattern.
You use the visitor design pattern when you want to perform a similar calculation on many different objects. It seems to confuse people, but I hope to solve that here. If you understand the concept of method overloading and the passing of objects back and forth for data access I don’t think you’ll have a problem. The code that follows should answer any questions you have.
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Code From the Video
SalesTrainee.java
public class SalesTrainee implements Visitable{
private int sickDays;
private int failedTests;
private double salary;
public SalesTrainee(int sickDays, int failedTests, double salary) {
this.sickDays = sickDays;
this.failedTests = failedTests;
this.salary = salary;
}
public double accept(Visitor visitor){
return visitor.visit(this);
}
// Getters & Setters
public int getSickDays() {
return sickDays;
}
public void setSickDays(int sickDays) {
this.sickDays = sickDays;
}
public int getFailedTests() {
return failedTests;
}
public void setFailedTests(int failedTests) {
this.failedTests = failedTests;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
}
Salesman.java
public class Salesman implements Visitable{
private double totalSalesAmount;
private int newCustomers;
public Salesman(double totalSalesAmount, int newCustomers) {
this.totalSalesAmount = totalSalesAmount;
this.newCustomers = newCustomers;
}
public double accept(Visitor visitor){
return visitor.visit(this);
}
// Getters & Setters
public double getTotalSalesAmount() {
return totalSalesAmount;
}
public void setTotalSalesAmount(double totalSalesAmount) {
this.totalSalesAmount = totalSalesAmount;
}
public int getNewCustomers() {
return newCustomers;
}
public void setNewCustomers(int newCustomers) {
this.newCustomers = newCustomers;
}
}
Boss.java
public class Boss implements Visitable{
private double totalSalesAmount;
private int newCustomers;
private double officeExpenses;
public Boss(double totalSalesAmount, int newCustomers, double officeExpenses) {
this.totalSalesAmount = totalSalesAmount;
this.newCustomers = newCustomers;
this.officeExpenses = officeExpenses;
}
public double accept(Visitor visitor){
return visitor.visit(this);
}
// Getters & Setters
public double getTotalSalesAmount() {
return totalSalesAmount;
}
public void setTotalSalesAmount(double totalSalesAmount) {
this.totalSalesAmount = totalSalesAmount;
}
public int getNewCustomers() {
return newCustomers;
}
public void setNewCustomers(int newCustomers) {
this.newCustomers = newCustomers;
}
public double getOfficeExpenses() {
return officeExpenses;
}
public void setOfficeExpenses(double officeExpenses) {
this.officeExpenses = officeExpenses;
}
}
Visitable.java
// Allows the Visitor to pass in an object
// so the right calculations are done
// depending on the object type
// accept() is in each employee object. Those
// employee objects then pass an object of their
// specific type to a concrete visitor. The concrete
// visitors contain a method named visit that is
// overloaded to handle each of the employee types
// and can then perform different calculations based
// on the employee type.
interface Visitable {
public double accept(Visitor visitor);
}
Visitor.java
// Each concrete visitor type will implement
// the Visitor interface. Here we define every
// instance of method overloading needed
interface Visitor {
public double visit(SalesTrainee trainee);
public double visit(Salesman salesman);
public double visit(Boss boss);
}
YearlyBonusVisitor.java
public class YearlyBonusVisitor implements Visitor{
public double visit(SalesTrainee trainee) {
System.out.println("Trainees Yearly Bonus");
// Find bonus percentage using ternary operator
double yearlyBonusPercentage = (trainee.getSickDays() < 10 && trainee.getFailedTests() < 2) ? .10 : .02;
double yearlyBonusAmount = trainee.getSalary() * yearlyBonusPercentage;
return yearlyBonusAmount;
}
public double visit(Salesman salesman) {
System.out.println("Salesmans Yearly Bonus");
double yearlyBonusPercentage = (salesman.getTotalSalesAmount() > 100000 && salesman.getNewCustomers() > 50) ? .12 : .04;
double yearlyBonusAmount = salesman.getTotalSalesAmount() * yearlyBonusPercentage;
return yearlyBonusAmount;
}
public double visit(Boss boss) {
System.out.println("Bosses Yearly Bonus");
double yearlyBonusPercentage = (boss.getOfficeExpenses() < 50000 && boss.getNewCustomers() > 1000) ? .15 : .04;
double yearlyBonusAmount = boss.getTotalSalesAmount() * yearlyBonusPercentage;
return yearlyBonusAmount;
}
}
QuarterlyBonusVisitor.java
public class QuarterlyBonusVisitor implements Visitor{
public double visit(SalesTrainee trainee) {
System.out.println("Trainees Yearly Bonus");
// Find bonus percentage using ternary operator
double quarterlyBonusPercentage = (trainee.getSickDays() < 2 && trainee.getFailedTests() < 1) ? .01 : 0;
double quarterlyBonusAmount = trainee.getSalary() * quarterlyBonusPercentage;
return quarterlyBonusAmount;
}
public double visit(Salesman salesman) {
System.out.println("Salesmans Yearly Bonus");
double quarterlyBonusPercentage = (salesman.getTotalSalesAmount() > 25000 && salesman.getNewCustomers() > 20) ? .03 : 0;
double quarterlyBonusAmount = salesman.getTotalSalesAmount() * quarterlyBonusPercentage;
return quarterlyBonusAmount;
}
public double visit(Boss boss) {
System.out.println("Bosses Yearly Bonus");
double quarterlyBonusPercentage = (boss.getOfficeExpenses() < 12000 && boss.getNewCustomers() > 250) ? .05 : .01;
double quarterlyBonusAmount = boss.getTotalSalesAmount() * quarterlyBonusPercentage;
return quarterlyBonusAmount;
}
}
TestBonusCalculator.java
public class TestBonusCalculator {
public static void main(String[] args){
// We can have completely different calculations performed
// on completely different objects just by defining a
// new concrete Visitor
YearlyBonusVisitor yearlyBonusCalculator = new YearlyBonusVisitor();
SalesTrainee bradTrainee = new SalesTrainee(5, 1, 20000);
Salesman tomSalesman = new Salesman(150000, 62);
Boss rossBoss = new Boss(1000000, 1200, 4000000);
System.out.println("YEARLY BONUS");
System.out.println(bradTrainee.accept(yearlyBonusCalculator));
System.out.println(tomSalesman.accept(yearlyBonusCalculator));
System.out.println(rossBoss.accept(yearlyBonusCalculator));
// Calculate Quarterly Bonus
QuarterlyBonusVisitor quarterlyBonusCalculator = new QuarterlyBonusVisitor();
bradTrainee = new SalesTrainee(1, 0, 20000);
tomSalesman = new Salesman(30000, 22);
rossBoss = new Boss(200000, 300, 11000);
System.out.println("\nQUARTERLY BONUS");
System.out.println(bradTrainee.accept(quarterlyBonusCalculator));
System.out.println(tomSalesman.accept(quarterlyBonusCalculator));
System.out.println(rossBoss.accept(quarterlyBonusCalculator));
}
}
Hey Derek, plz change the variables names on QuarterlyBonusVisitor.java, it says yearlyBonusAmount.
I fixed it. Thanks for pointing that out. You have a very good eye for my mistakes 🙂
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