2003 AP Computer Science A Question 2, Java
Periodically, a company processes the retirement of some of its
employees. In this question, you will write methods to help the company
determine whether an employee is eligible to retire and to process the
retirement of all eligible employees.
The Java interface Employee is implemented by
objects that represent employees. The interface is declared
as follows.
<![CDATA[
public interface Employee
{
public int getAge(); // returns age of employee
public int getYearsOnJob(); // returns number of years on job
public double getSalary(); // returns salary in dollars
public int getID(); // returns unique employee ID number
}
]]>
The Company class is declared as follows.
<![CDATA[
import java.util.ArrayList;
public class Company
{
// minimum age, years on job, and salary needed to retire
private final static int RETIRE_AGE = 65;
private final static int RETIRE_YEARS = 30;
private final static double RETIRE_SALARY = 10000.0;
private ArrayList myEmployees; // list of employees
private double myTotalSalary; // total salary of all employees
// ... constructor and other methods not shown
// postcondition: returns true if emp is eligible to retire;
// otherwise, returns false
private boolean employeeIsEligible(Employee emp)
{
// you will write this function
}
// postcondition: all retirement-eligible employees have been
// removed from myEmployees; myEmployees remains
// sorted by employee ID; myTotalSalary has been
// updated to maintain invariant that it represents
// total of all employee salaries
public void processRetirements()
{
// you will write this function
}
}
]]>
Two class invariants must be maintained by Company objects:
- The instance variable
myEmployees is sorted by
employee ID.
- The instance variable
myTotalSalary is the total
of all employee salaries.
The Company constructor will establish these invariants as
true initially. All Company methods must ensure that the
invariants remain true.
Part A
An employee is eligible for retirement if (s)he meets at least two
of the following requirements.
- The employee is at least
RETIRE_AGE years old.
- The employee has worked for at least
RETIRE_YEARS
years.
- The employee's salary is at least
RETIRE_SALARY.
Write the private Company method
employeeIsEligible, which is described as follows.
Method employeeIsEligible returns a boolean value
that indicates whether the employee represented by parameter
emp is eligible for retirement, using the rules above.
Complete method employeeIsEligible below.
<![CDATA[
// postcondition: returns true if emp is eligible to retire;
// otherwise, returns false
private boolean employeeIsEligible(Employee emp)
{
}
]]>
Part B
( Assume all import statements you need are made. You do
not need to write import statements).
Write the Company method processRetirements,
which is described as follows. Method processRetirements
removes all retirement-eligible emloyees from ArrayList
myEmployees and maintains the two class invariants described
above: the ArrayList is maintained in order by employee ID and
myTotalSalary is the total of all salaries of the remaining
employees.
In writing processRetirements, you may call
method employeeIsEligible, specified in part (a). Assume
that employeeIsEligible works as specified, regardless of
what you wrote in part (a).
Complete method processRetirements below.
<![CDATA[
// postcondition: all retirement-eligible employees have been
// removed from myEmployees; myEmployees remains
// sorted by employee ID; myTotalSalary has been
// updated to maintain invariant that it represents
// total of all employee salaries
public void processRetirements()
{
}
]]>
Owen L. Astrachan
Last modified: Wed May 14 16:39:13 EDT 2003