1. Reference Variables

Part 1: Memory Map: Account Class

Part 1: Memory Map: Account Class

Show Collapsed Show Notes Show Solutions Full Page Print Max Width Show All Hide All

Note

To show solutions, you will need to toggle “Show Solutions” above.

You should assume the class below exists and is in scope for the questions in this subsection:

Listing 1 in Account.java

public class Account {

   private String accountType;
   private int hoursWorked;
   private double hourlyRate;

   public Account(String accountType, int hoursWorked, double hourlyRate) {
      // assume appropriate error handling...
      this.accountType = accountType;
      this.hoursWorked = hoursWorked;
      this.hourlyRate = hourlyRate;
   } // Account

   public int getHoursWorked() {
      return this.hoursWorked;
   } // getHoursWorked

   public double getHourlyRate() {
      return this.hourlyRate;
   } // getHourlyRate

} // Account

Question 1

Draw the memory map that represents the state of the variables after the following code executes:

Account acct1 = new Account("Salary", 40, 50.0);
Account acct2 = new Account("Hourly", 20, 25.0);

Solution

Your memory map should look similar to the following:

Question 2

Draw the memory map that represents the state of the variables after the following code executes:

Account acct1 = new Account("Salary", 40, 50.0);
Account acct2 = new Account("Hourly", 20, 25.0);
acct1 = acct2;

Solution

Your memory map should look similar to the following:

Question 3

What would be output from the following code?

Account acct1 = new Account("Salary", 40, 50.0);
Account acct2 = new Account("Hourly", 20, 25.0);
acct1 = acct2;
acct1.setHoursWorked(15); // assume the setter exists and works as expected
System.out.println(acct1.getHoursWorked());
System.out.println(acct2.getHoursWorked());

Solution

The program would output:

15
15

since both references point to the same object and we updated the hours worked to be 15.

Question 4

Draw the memory map that represents the state of the variables after the following code executes:

Account[] accounts = new Account[3];

Solution

Your memory map should look similar to the following:

Question 5

Draw the memory map that represents the state of the variables after the following code executes:

Account[] accounts = new Account[2];

accounts[0] = new Account("Salary", 40, 50.0);
accounts[1] = new Account("Hourly", 10, 15.0);

Solution

Your memory map should look similar to the following:

Part 2: Memory Map: Payroll Class

Part 2: Memory Map: Payroll Class

Show Collapsed Show Notes Show Solutions Full Page Print Max Width Show All Hide All

You should assume the class below exists and is in scope for the questions in this subsection. You should also assume that the Account class from the previous subsection exists and is in scope.

Listing 2 in Payroll.java

public class Payroll {
   private Account[] employeeAccounts;

   public Payroll(Account[] accounts) {
      this.employeeAccounts = accounts;
   } // Payroll

} // Payroll

Question 1

Draw the memory map that represents the state of the variables after the following code executes.

Account[] accounts = new Account[3];

accounts[0] = new Account("Salary", 40, 50.0);
accounts[1] = new Account("Hourly", 10, 15.0);

Account accounts2 = new Account("Contractor", 30, 60.0);

Payroll payroll = new Payroll(accounts);

Solution

Your memory map should look similar to the following:

Question 2

Write a method called calculateTotalHoursWorked inside of Payroll.java that calculates the total hours worked for all employee accounts.

Solution

Here is one possible solution:

public int calculateTotalHoursWorked() {
   int total = 0;
   for (Account acc : employeeAccounts) {
      if (acc != null) {
         total += acc.getHoursWorked();
      } // if
   } // for
   return total;
} // calculateTotalHoursWorked

Question 3

What will be output if we execute the following line after the code in the previous question:

Listing 3 Executed after payroll has been created

System.out.println(payroll.calculateTotalHoursWorked());

Solution

The program should output 50 for the total hours worked.

Question 4

Write a method called calculateTotalPay inside of Payroll.java that calculates the total pay for all employee accounts.

Solution

One Possible Solution:

Listing 4 in Payroll.java

public double calculateTotalPay() {
   double total = 0;
   for (Account acc : employeeAccounts) {
      if (acc != null) {
         total += acc.getHoursWorked() * acc.getHourlyRate();
      } // if
   } // for
   return total;
} // calculateTotalPay