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question 1
In this project you need to write software for UIC's finance office. The finance office deals with the finances of different
kinds of people at UIC: students who pay money for their tuitions, employees who receive money for their salaries, etc.
All these people pay or receive a certain amount of money, expressed in yuans.
Write a Payer interface for people who pay money to the finance office, with the following UML specification:
+-------------------------------+
| <> |
| Payer |
+-------------------------------+
| + getName(): String |
| + getDebt(): int |
| + pay(int amount): void |
+-------------------------------+
and a Person class that implements Payer and has the following UML specification:
+------------------------------------+
| Person |
+------------------------------------+
| - name: String |
| - debt: int |
+------------------------------------+
| + Person(String name, int debt) |
| + getName(): String |
| + getDebt(): int |
| # setDebt(int debt): void |
| + pay(int amount): void |
| + testPerson(): void |
+------------------------------------+
The name instance variable indicates the name of the Person. The debt instance variable indicates the amount of money
that the person must pay to UIC (to simplify the assignment we will assume that money is always expressed as an integer
number of yuans).
The setDebt method changes the amount of debt that a person has. The setDebt method is protected, not
public. This means that only subclasses of the Person class can use the setDebt method. All the other classes in the
software cannot use the setDebt method, so they cannot change the amount of debt a person has, which is good for
security.
The purpose of the pay method is to decrease or increase the amount of debt a person has (depending on what kind of
person it is) by the amount given as argument to the method. The pay method of the Person class is abstract, since
we do not know what kind of person the person is (a person paying money or a person receiving money). question 2
Add a class Student that extends Person. The constructor of the Student class takes as arguments a name and the
amount of UIC debt that the student has (because the student needs to pay tuition or pay for the dormitory, for example).
The Student class does not have any instance variable.
The pay method of the Student class makes the student pay money to UIC, which decreases the amount of debt that
the student has by the amount of money given as argument to the method. A student can have a negative debt (meaning
that the student paid too much to UIC, which always makes UIC happy).
question 3
Add a class Employee that extends Person. The constructor of the Employee class takes as arguments the name of
the employee and the salary that UIC must pay to the employee. If the salary given as argument is strictly less than zero
then the constructor must throw a NegativeSalaryException with the message "An employee cannot have
a negative salary!" The Employee class does not have any instance variable.
Warning: the constructor of the Employee class takes as argument the salary of the employee (the amount of money
that UIC must pay to the employee) but the debt instance variable of the Person class indicates how much money the
person must pay to UIC. Therefore a positive salary is the same as a negative debt.
The pay method of the Employee class makes UIC pay money to the employee, which decreases the current salary of
the employee by the amount of money given as argument to the method (so the debt of the employee becomes less
negative!) For example, if an employee currently has a salary of 10000 yuans (-10000 yuans of debt) and pay(2000) is
called then the employee's salary becomes 8000 yuans (-8000 yuans of debt, meaning that UIC still needs to pay an extra
8000 yuans to the employee after paying the 2000 yuans). It is fine for the pay method to be given a negative value as
argument, which means the employee then just receives a salary increase. For example, if an employee currently has a
salary of 10000 yuans and pay(-2000) is called then the employee's salary becomes 12000 yuans. An employee cannot
be overpaid money by UIC though, so the current salary of the employee must always be positive or zero, never negative
(the debt of the employee cannot be positive). If the argument given to the pay method is too positive and would change
the employee's salary to become negative, then instead the current salary of the employee must not change and the pay
method must throw a NegativeSalaryException with the message "An employee cannot be overpaid
by XXX yuans!", where XXX is replaced with the amount of the overpayment. For example, if an employee currently
has a salary of 10000 yuans and pay(12000) is called then the employee still has a salary of 10000 yuans and the
method throws a NegativeSalaryException with the message "An employee cannot be overpaid by
2000 yuans!"
Note: to simplify the project, do not worry about the setDebt method.
Change other classes and interfaces as necessary.
question 4
Add a class FacultyMember that extends Employee. The constructor of the FacultyMember class takes as
arguments the name of the faculty member and the salary that UIC must pay to the faculty member. The
FacultyMember class does not have any instance variable.
The pay method of the FacultyMember class makes UIC pay money to the faculty member, which decreases the
current salary of the faculty member by the amount of money given as argument to the method (so the debt of the faculty member becomes less negative!) In addition to the normal salary, a faculty member might also temporarily borrow extra
money from UIC that the faculty member will need to reimburse later, so the salary of a faculty member might then
become negative (the debt becomes positive) without throwing any exception: a negative salary (positive debt) then just
means that the faculty member has temporarily borrowed some money.
Change other classes and interfaces as necessary.
question 5
Add a FinanceOffice class with the following UML specification:
+--------------------------------------------+
| FinanceOffice |
+--------------------------------------------+
| - name: String |
| - payers: ArrayList |
+--------------------------------------------+
| + FinanceOffice(String name) |
| + addPayer(Payer payer): void |
| + totalDebt(): int |
| + getDebt(String name): int |
| + pay(String name, int amount): void |
| + testFinanceOffice(): void |
+--------------------------------------------+
When a finance office is created, it has an arraylist of payers but the arraylist is empty (the arraylist does not contain any
payer).
The addPayer method takes a payer as argument and adds the payer to the arraylist of payers for the finance office.
The totalDebt method returns as result the total amount of debt of all the payers of the finance office (if the result is
positive then it means that the finance office will receive more money from all the students (and the faculty members
with debts) than it needs money to pay all the salaries of the employees and UIC will then make a profit; if the result is
negative then it means that the finance office will not get enough money from the students and will need to borrow extra
money from a bank to be able to pay all the employees, otherwise UIC will go bankrupt; if the result is zero then it means
that the money paid by all the students will exactly cover the salaries of the employees).
The getDebt method takes as argument the name of a payer and returns as result the current amount of debt for this
payer. If the finance office does not have a payer with the correct name then the getDebt method must throw an
UnknownPayerException with the message "Payer XXX unknown", where XXX is replaced with the name of
the payer. Do not worry about multiple payers having the same name.
The pay method takes as argument the name of a payer and an amount of money and uses the pay method of that payer
to pay that amount of money to that payer. If the finance office does not have a payer with the correct name then the
pay method must throw an UnknownPayerException with the message "Payer XXX unknown", where XXX is
replaced with the name of the payer. Do not worry about multiple payers having the same name.
Note: the pay method does not catch any exception, it only throws exceptions.
question 6
In this question and the next one we want to create a command line interface (CLI) for our finance office software. Add a CLI class with a main method. Your code then has two classes with a main method: the Test class that you can
use to run all your tests for all your classes, and the CLI class that you will now use to run the interactive text-based
interface of your program.
The CLI class does not have any testCLI method because this class is only used to allow users to use the software
interactively.
Add to the CLI class a private static input instance variable which is a Scanner object that reads input from the
standard input stream System.in:
private static Scanner input = new Scanner(System.in);
Always use this input scanner object when you need to read input. (Never close this scanner object, because this would
also close the standard input stream System.in, and then the next time you tried to read something from the standard
input stream you would get a NoSuchElementException!)
In addition to the main method and the input instance variable, the CLI class has two methods called readLine and
readPosInt.
The readLine method is static and private, it takes a string as argument, and returns another string as result. The
readPosInt method is static and private, it takes a string as argument, and returns a positive integer as result.
The readLine method uses System.out.print (not println) to print its string argument on the screen (later
when we use the readLine method, the string argument of the method will be a message telling the user to type some
text). Then the readLine method uses the input scanner object to read a whole line of text from the user of the
program and returns the text as result.
The readPosInt method uses System.out.print (not println) to print its string argument on the screen (later
when we use the readPosInt method, the string argument of the method will be a message telling the user to type some
integer). Then the readPosInt method uses the input scanner object to read an integer from the user of the program.
After reading the integer, the readPosInt method must also use the scanner's nextLine method to read the single
newline character that comes from the user pressing the Enter key on the keyboard after typing the integer (if you do
not read this newline character using the nextLine method inside the readPosInt method, then the newline
character will remain in the input stream, and, the next time you use the readLine method described above, the
readLine method will just immediately read only the newline character from the input stream and return an empty
string as result, without waiting for the user to type anything!)
If the user types something which is not an integer, then the nextInt method of the scanner will throw an
InputMismatchException. In that case the code of your readPosInt method must catch the exception, use
System.out.println to print the error message "You must type an integer!" to the user (use
System.out.println for this, not System.err.println, otherwise you might hit a bug in Eclipse...), use the
scanner's nextLine method to read (and ignore) the wrong input typed by the user of the program (if you do not do
this, the wrong input typed by the user will remain in the input stream, and the next time you call the nextInt method
again, you will get an InputMismatchException again!), and then do the whole thing again (including printing again
the string argument of the readPosInt method) to try to read an integer again (hint: put the whole code of the method
inside a while loop).
After reading the integer and the newline character (which is just ignored), the readPosInt method tests the integer.
If the integer is bigger than or equal to zero, then the readPosInt method returns the integer as result. If the integer is strictly less than zero, then the readPosInt method uses System.out.println to print the error message
"Positive integers only!" to the user (use System.out.println for this, not System.err.println,
otherwise you might hit a bug in Eclipse...), and then does the whole thing again (including printing again the string
argument of the readPosInt method) to try to read an integer again (hint: just print the error message, and then the
while loop you already have around the whole code will automatically do the whole thing again...)
For example, if you want to check that your two methods readLine and readPosInt work correctly, put the following
code in the main method of your CLI class:
public static void main(String[] args) {
String str1 = readLine("Type some text: ");
System.out.println("Text read is: " + str1);
int i = readPosInt("Type an integer: ");
System.out.println("Integer read is: " + i);
String str2 = readLine("Type some text again: ");
System.out.println("Text read is: " + str2);
}
then running the main method of the CLI class should look like this (where aaaa bbbb, cccc, dddd eeee, -100,
-200, 1234, and ffff gggg are inputs typed by the user on the keyboard):
Type some text: aaaa bbbb
Text read is: aaaa bbbb
Type an integer: cccc
You must type an integer!
Type an integer: dddd eeee
You must type an integer!
Type an integer: -100
Positive integers only!
Type an integer: -200
Positive integers only!
Type an integer: 1234
Integer read is: 1234
Type some text again: ffff gggg
Text read is: ffff gggg
question 7
Once you have checked that your methods readLine and readPosInt work correctly, remove all the code inside the
main method of the CLI class so that the main method is empty again.
In the rest of this question, use the readLine and readPosInt methods every time your program needs to read a
string or an integer from the user.
In the empty main method of the CLI class, create a single FinanceOffice object with the name "UIC FO". The
main method of the CLI class must then print a menu that allows the user of your software to do six different actions
that involve the finance office object, and your program must then read an integer from the user that indicates which
action must be performed by the program (see below for the details of each action). Use the readPosInt method to
print the menu (give the string for the menu as the argument of readPosInt) and to read the integer typed by the user.
For example, the menu should look like this:
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
The user then types an integer between 1 and 6 to select the action. For example (where 3 is an input from the user):
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
and your program then performs the selected action.
After an action has been performed by your program, your program must again print the menu and ask again the user of
the program for the next action to perform (hint: put the whole code of the main method inside a while loop, except
for the one line of code that creates the single finance office object).
If the user types an integer which is not between 1 and 6, then your program must print an error message "Unknown
action!" to the user (hint: when testing the integer for the action, use the default case of a switch statement)
and then print the menu again (by just going back to the beginning of the while loop).
For example (where 7 is an input from the user):
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 7
Unknown action!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
If the user types something which is not an integer, the readPosInt method that you implemented in the previous
question will automatically repeat the menu and ask the user to type an integer again until the user actually types an
integer, so you do not have to worry about this in the code of the main method of your CLI class.
For example (where aaaa and bbbb cccc are inputs from the user):
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): aaaa
You must type an integer!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): bbbb cccc
You must type an integer!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
Here are the detailed explanations for each action.
Action 1: printing the total amount of debt.
When the user of the software specifies action 1, your program must simply print on the screen the total amount of debt
for all the payers of the finance office. Then your program goes back to printing the menu of actions (by just going back
to the beginning of the while loop).
For example (where 1 is an input from the user):
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 2000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
Action 2: adding a new payer to the finance office.
When the user of the software specifies action 2, your program must add a new payer to the finance office. To add a new
payer, your program needs to ask the user three things: the type of payer (an integer read using readPosInt: the integer
1 represents a student, the integer 2 represents an employee, the integer 3 represents a faculty member, and any other
integer must result in an error message "Unknown type of payer!" being printed and the software going
immediately back to the main menu), the name of the payer (a string read using readLine), and the initial amount of
money for the debt (for a student) or the salary (for an employee or a faculty member) when the payer is created. You
program must then create the correct payer, add it to the finance office, and print an information message for the user of
the software. The program then goes back to the menu. For example (where 1, 2, -100, 4, 2, 1, UIC Student, 5000, 1, 2, 2, Daniel, 1000, 1, 2, 3, Thompson, 2000, and
1 are inputs from the user):
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 0
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 2
Enter the payer type (student:1 employee:2 faculty member:3): -100
Positive integers only!
Enter the payer type (student:1 employee:2 faculty member:3): 4
Unknown type of payer!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 2
Enter the payer type (student:1 employee:2 faculty member:3): 1
Enter the name of the payer: UIC Student
Enter the initial amount of money: 5000
Student "UIC Student" with 5000 yuans of debt added
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 5000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 2
Enter the payer type (student:1 employee:2 faculty member:3): 2
Enter the name of the payer: Daniel
Enter the initial amount of money: 1000
Employee "Daniel" with 1000 yuans of salary added
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 4000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 2
Enter the payer type (student:1 employee:2 faculty member:3): 3
Enter the name of the payer: Thompson
Enter the initial amount of money: 2000
Faculty member "Thompson" with 2000 yuans of salary added
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 2000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
Note that the readPosInt method prevents the initial amount of money from being negative, so the constructor for
the Employee class will never throw a NegativeSalaryException when you create an employee object.
Nevertheless the code of the main method of your CLI class must handle this exception correctly by printing the error
message "BUG! This must never happen!" and immediately terminating the program using System.exit(1).
The same applies to a faculty member.
Action 3: listing the amount of debt for a given payer.
When the user of the software specifies action 3, your program must ask the user to type the name of a payer, and the
program then prints the amount of debt for this payer.
For example (where 3, UIC Student, 3, Daniel, 3, and Thompson are inputs from the user):
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: UIC Student
UIC Student has 5000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Daniel
Daniel has -1000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Thompson
Thompson has -2000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
If the name of the payer is wrong (the finance office does not have a payer with this name) then an
UnknownPayerException will be thrown by the FinanceOffice object. The code of the main method of your CLI class must then catch this exception, print the error message from the exception object, and then it just goes back to
printing the menu of actions (by just going back to the beginning of the while loop).
For example (where 3 and aaaa are inputs from the user):
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: aaaa
Payer aaaa unknown
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
Action 4: paying money to a given payer.
When the user of the software specifies action 4, your program must ask the user to type the name of a payer and an
amount of money, and the program then uses that amount of money to call the pay method of the payer with that name.
Then the program goes back to the main menu.
For example:
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: UIC Student
UIC Student has 5000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 4
Enter the name of the payer: UIC Student
Enter the amount of money: 1000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: UIC Student
UIC Student has 4000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Daniel
Daniel has -1000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 4
Enter the name of the payer: Daniel
Enter the amount of money: -500
Positive integers only!
Enter the amount of money: 500
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Daniel
Daniel has -500 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Thompson
Thompson has -2000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 4
Enter the name of the payer: Thompson
Enter the amount of money: 500
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Thompson
Thompson has -1500 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
If the name of the payer is wrong (the finance office does not have a payer with this name) then an
UnknownPayerException will be thrown by the FinanceOffice object. The code of the main method of your
CLI class must then catch this exception, print the error message from the exception object, and then it just goes back to
printing the menu of actions (by just going back to the beginning of the while loop).
For example:
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 4
Enter the name of the payer: aaaa
Enter the amount of money: 1000
Payer aaaa unknown Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
If a payer is an employee and the amount of money typed by the user is too big then a NegativeSalaryException
will be thrown by the Employee object. The code of the main method of your CLI class must then catch this exception,
print the error message from the exception object, and then it just goes back to printing the menu of actions (by just going
back to the beginning of the while loop).
For example:
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Daniel
Daniel has -500 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 4
Enter the name of the payer: Daniel
Enter the amount of money: 1500
An employee cannot be overpaid by 1000 yuans!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Daniel
Daniel has -500 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: UIC Student
UIC Student has 4000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 4
Enter the name of the payer: UIC Student
Enter the amount of money: 5000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: UIC Student
UIC Student has -1000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Thompson
Thompson has -1500 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 4
Enter the name of the payer: Thompson
Enter the amount of money: 2000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Thompson
Thompson has 500 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
Action 5: taking money from a given payer.
When the user of the software specifies action 5, your program must ask the user to type the name of a payer and an
amount of money, and the program then uses that amount of money, makes it negative, and pays that negative amount
to the payer with that name. Then the program goes back to the main menu.
For example:
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: UIC Student
UIC Student has 4000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 5
Enter the name of the payer: UIC Student
Enter the amount of money: 1000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: UIC Student
UIC Student has 5000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Daniel
Daniel has -500 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 5
Enter the name of the payer: Daniel Enter the amount of money: -500
Positive integers only!
Enter the amount of money: 500
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Daniel
Daniel has -1000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Thompson
Thompson has -1500 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 5
Enter the name of the payer: Thompson
Enter the amount of money: 500
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Thompson
Thompson has -2000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
If the name of the payer is wrong (the finance office does not have a payer with this name) then an
UnknownPayerException will be thrown by the FinanceOffice object. The code of the main method of your
CLI class must then catch this exception, print the error message from the exception object, and then it just goes back to
printing the menu of actions (by just going back to the beginning of the while loop).
For example:
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 5
Enter the name of the payer: aaaa
Enter the amount of money: 1000
Payer aaaa unknown
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
Note that, even if a payer is an employee, the readPosInt method prevents the amount of money typed by the user
from being negative. This means an employee will never throw a NegativeSalaryException. Nevertheless the code
of the main method of your CLI class must handle this exception by printing the error message "BUG! This must
never happen!" and immediately terminating the program using System.exit(1).
Action 6: quitting the program.
When the user of the software specifies action 6, your program must print a "Goodbye!" message, and terminate the
program using: System.exit(0).
For example (where 6 is an input from the user):
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 6
Goodbye!
Here is a more complete example of running the software:
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): aaaa
You must type an integer!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): bbbb cccc
You must type an integer!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): -100
Positive integers only!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 7
Unknown action!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 0
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 2
Enter the payer type (student:1 employee:2 faculty member:3): -100
Positive integers only! Enter the payer type (student:1 employee:2 faculty member:3): 4
Unknown type of payer!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 2
Enter the payer type (student:1 employee:2 faculty member:3): 1
Enter the name of the payer: UIC Student
Enter the initial amount of money: 5000
Student "UIC Student" with 5000 yuans of debt added
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 5000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 2
Enter the payer type (student:1 employee:2 faculty member:3): 2
Enter the name of the payer: Daniel
Enter the initial amount of money: 1000
Employee "Daniel" with 1000 yuans of salary added
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 4000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 2
Enter the payer type (student:1 employee:2 faculty member:3): 3
Enter the name of the payer: Thompson
Enter the initial amount of money: 2000
Faculty member "Thompson" with 2000 yuans of salary added
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 2000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: UIC Student
UIC Student has 5000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Daniel
Daniel has -1000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Thompson
Thompson has -2000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: aaaa
Payer aaaa unknown
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 4
Enter the name of the payer: UIC Student
Enter the amount of
question 1
In this project you need to write software for UIC's finance office. The finance office deals with the finances of different
kinds of people at UIC: students who pay money for their tuitions, employees who receive money for their salaries, etc.
All these people pay or receive a certain amount of money, expressed in yuans.
Write a Payer interface for people who pay money to the finance office, with the following UML specification:
+-------------------------------+
| <
| Payer |
+-------------------------------+
| + getName(): String |
| + getDebt(): int |
| + pay(int amount): void |
+-------------------------------+
and a Person class that implements Payer and has the following UML specification:
+------------------------------------+
| Person |
+------------------------------------+
| - name: String |
| - debt: int |
+------------------------------------+
| + Person(String name, int debt) |
| + getName(): String |
| + getDebt(): int |
| # setDebt(int debt): void |
| + pay(int amount): void |
| + testPerson(): void |
+------------------------------------+
The name instance variable indicates the name of the Person. The debt instance variable indicates the amount of money
that the person must pay to UIC (to simplify the assignment we will assume that money is always expressed as an integer
number of yuans).
The setDebt method changes the amount of debt that a person has. The setDebt method is protected, not
public. This means that only subclasses of the Person class can use the setDebt method. All the other classes in the
software cannot use the setDebt method, so they cannot change the amount of debt a person has, which is good for
security.
The purpose of the pay method is to decrease or increase the amount of debt a person has (depending on what kind of
person it is) by the amount given as argument to the method. The pay method of the Person class is abstract, since
we do not know what kind of person the person is (a person paying money or a person receiving money). question 2
Add a class Student that extends Person. The constructor of the Student class takes as arguments a name and the
amount of UIC debt that the student has (because the student needs to pay tuition or pay for the dormitory, for example).
The Student class does not have any instance variable.
The pay method of the Student class makes the student pay money to UIC, which decreases the amount of debt that
the student has by the amount of money given as argument to the method. A student can have a negative debt (meaning
that the student paid too much to UIC, which always makes UIC happy).
question 3
Add a class Employee that extends Person. The constructor of the Employee class takes as arguments the name of
the employee and the salary that UIC must pay to the employee. If the salary given as argument is strictly less than zero
then the constructor must throw a NegativeSalaryException with the message "An employee cannot have
a negative salary!" The Employee class does not have any instance variable.
Warning: the constructor of the Employee class takes as argument the salary of the employee (the amount of money
that UIC must pay to the employee) but the debt instance variable of the Person class indicates how much money the
person must pay to UIC. Therefore a positive salary is the same as a negative debt.
The pay method of the Employee class makes UIC pay money to the employee, which decreases the current salary of
the employee by the amount of money given as argument to the method (so the debt of the employee becomes less
negative!) For example, if an employee currently has a salary of 10000 yuans (-10000 yuans of debt) and pay(2000) is
called then the employee's salary becomes 8000 yuans (-8000 yuans of debt, meaning that UIC still needs to pay an extra
8000 yuans to the employee after paying the 2000 yuans). It is fine for the pay method to be given a negative value as
argument, which means the employee then just receives a salary increase. For example, if an employee currently has a
salary of 10000 yuans and pay(-2000) is called then the employee's salary becomes 12000 yuans. An employee cannot
be overpaid money by UIC though, so the current salary of the employee must always be positive or zero, never negative
(the debt of the employee cannot be positive). If the argument given to the pay method is too positive and would change
the employee's salary to become negative, then instead the current salary of the employee must not change and the pay
method must throw a NegativeSalaryException with the message "An employee cannot be overpaid
by XXX yuans!", where XXX is replaced with the amount of the overpayment. For example, if an employee currently
has a salary of 10000 yuans and pay(12000) is called then the employee still has a salary of 10000 yuans and the
method throws a NegativeSalaryException with the message "An employee cannot be overpaid by
2000 yuans!"
Note: to simplify the project, do not worry about the setDebt method.
Change other classes and interfaces as necessary.
question 4
Add a class FacultyMember that extends Employee. The constructor of the FacultyMember class takes as
arguments the name of the faculty member and the salary that UIC must pay to the faculty member. The
FacultyMember class does not have any instance variable.
The pay method of the FacultyMember class makes UIC pay money to the faculty member, which decreases the
current salary of the faculty member by the amount of money given as argument to the method (so the debt of the faculty member becomes less negative!) In addition to the normal salary, a faculty member might also temporarily borrow extra
money from UIC that the faculty member will need to reimburse later, so the salary of a faculty member might then
become negative (the debt becomes positive) without throwing any exception: a negative salary (positive debt) then just
means that the faculty member has temporarily borrowed some money.
Change other classes and interfaces as necessary.
question 5
Add a FinanceOffice class with the following UML specification:
+--------------------------------------------+
| FinanceOffice |
+--------------------------------------------+
| - name: String |
| - payers: ArrayList
+--------------------------------------------+
| + FinanceOffice(String name) |
| + addPayer(Payer payer): void |
| + totalDebt(): int |
| + getDebt(String name): int |
| + pay(String name, int amount): void |
| + testFinanceOffice(): void |
+--------------------------------------------+
When a finance office is created, it has an arraylist of payers but the arraylist is empty (the arraylist does not contain any
payer).
The addPayer method takes a payer as argument and adds the payer to the arraylist of payers for the finance office.
The totalDebt method returns as result the total amount of debt of all the payers of the finance office (if the result is
positive then it means that the finance office will receive more money from all the students (and the faculty members
with debts) than it needs money to pay all the salaries of the employees and UIC will then make a profit; if the result is
negative then it means that the finance office will not get enough money from the students and will need to borrow extra
money from a bank to be able to pay all the employees, otherwise UIC will go bankrupt; if the result is zero then it means
that the money paid by all the students will exactly cover the salaries of the employees).
The getDebt method takes as argument the name of a payer and returns as result the current amount of debt for this
payer. If the finance office does not have a payer with the correct name then the getDebt method must throw an
UnknownPayerException with the message "Payer XXX unknown", where XXX is replaced with the name of
the payer. Do not worry about multiple payers having the same name.
The pay method takes as argument the name of a payer and an amount of money and uses the pay method of that payer
to pay that amount of money to that payer. If the finance office does not have a payer with the correct name then the
pay method must throw an UnknownPayerException with the message "Payer XXX unknown", where XXX is
replaced with the name of the payer. Do not worry about multiple payers having the same name.
Note: the pay method does not catch any exception, it only throws exceptions.
question 6
In this question and the next one we want to create a command line interface (CLI) for our finance office software. Add a CLI class with a main method. Your code then has two classes with a main method: the Test class that you can
use to run all your tests for all your classes, and the CLI class that you will now use to run the interactive text-based
interface of your program.
The CLI class does not have any testCLI method because this class is only used to allow users to use the software
interactively.
Add to the CLI class a private static input instance variable which is a Scanner object that reads input from the
standard input stream System.in:
private static Scanner input = new Scanner(System.in);
Always use this input scanner object when you need to read input. (Never close this scanner object, because this would
also close the standard input stream System.in, and then the next time you tried to read something from the standard
input stream you would get a NoSuchElementException!)
In addition to the main method and the input instance variable, the CLI class has two methods called readLine and
readPosInt.
The readLine method is static and private, it takes a string as argument, and returns another string as result. The
readPosInt method is static and private, it takes a string as argument, and returns a positive integer as result.
The readLine method uses System.out.print (not println) to print its string argument on the screen (later
when we use the readLine method, the string argument of the method will be a message telling the user to type some
text). Then the readLine method uses the input scanner object to read a whole line of text from the user of the
program and returns the text as result.
The readPosInt method uses System.out.print (not println) to print its string argument on the screen (later
when we use the readPosInt method, the string argument of the method will be a message telling the user to type some
integer). Then the readPosInt method uses the input scanner object to read an integer from the user of the program.
After reading the integer, the readPosInt method must also use the scanner's nextLine method to read the single
newline character that comes from the user pressing the Enter key on the keyboard after typing the integer (if you do
not read this newline character using the nextLine method inside the readPosInt method, then the newline
character will remain in the input stream, and, the next time you use the readLine method described above, the
readLine method will just immediately read only the newline character from the input stream and return an empty
string as result, without waiting for the user to type anything!)
If the user types something which is not an integer, then the nextInt method of the scanner will throw an
InputMismatchException. In that case the code of your readPosInt method must catch the exception, use
System.out.println to print the error message "You must type an integer!" to the user (use
System.out.println for this, not System.err.println, otherwise you might hit a bug in Eclipse...), use the
scanner's nextLine method to read (and ignore) the wrong input typed by the user of the program (if you do not do
this, the wrong input typed by the user will remain in the input stream, and the next time you call the nextInt method
again, you will get an InputMismatchException again!), and then do the whole thing again (including printing again
the string argument of the readPosInt method) to try to read an integer again (hint: put the whole code of the method
inside a while loop).
After reading the integer and the newline character (which is just ignored), the readPosInt method tests the integer.
If the integer is bigger than or equal to zero, then the readPosInt method returns the integer as result. If the integer is strictly less than zero, then the readPosInt method uses System.out.println to print the error message
"Positive integers only!" to the user (use System.out.println for this, not System.err.println,
otherwise you might hit a bug in Eclipse...), and then does the whole thing again (including printing again the string
argument of the readPosInt method) to try to read an integer again (hint: just print the error message, and then the
while loop you already have around the whole code will automatically do the whole thing again...)
For example, if you want to check that your two methods readLine and readPosInt work correctly, put the following
code in the main method of your CLI class:
public static void main(String[] args) {
String str1 = readLine("Type some text: ");
System.out.println("Text read is: " + str1);
int i = readPosInt("Type an integer: ");
System.out.println("Integer read is: " + i);
String str2 = readLine("Type some text again: ");
System.out.println("Text read is: " + str2);
}
then running the main method of the CLI class should look like this (where aaaa bbbb, cccc, dddd eeee, -100,
-200, 1234, and ffff gggg are inputs typed by the user on the keyboard):
Type some text: aaaa bbbb
Text read is: aaaa bbbb
Type an integer: cccc
You must type an integer!
Type an integer: dddd eeee
You must type an integer!
Type an integer: -100
Positive integers only!
Type an integer: -200
Positive integers only!
Type an integer: 1234
Integer read is: 1234
Type some text again: ffff gggg
Text read is: ffff gggg
question 7
Once you have checked that your methods readLine and readPosInt work correctly, remove all the code inside the
main method of the CLI class so that the main method is empty again.
In the rest of this question, use the readLine and readPosInt methods every time your program needs to read a
string or an integer from the user.
In the empty main method of the CLI class, create a single FinanceOffice object with the name "UIC FO". The
main method of the CLI class must then print a menu that allows the user of your software to do six different actions
that involve the finance office object, and your program must then read an integer from the user that indicates which
action must be performed by the program (see below for the details of each action). Use the readPosInt method to
print the menu (give the string for the menu as the argument of readPosInt) and to read the integer typed by the user.
For example, the menu should look like this:
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
The user then types an integer between 1 and 6 to select the action. For example (where 3 is an input from the user):
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
and your program then performs the selected action.
After an action has been performed by your program, your program must again print the menu and ask again the user of
the program for the next action to perform (hint: put the whole code of the main method inside a while loop, except
for the one line of code that creates the single finance office object).
If the user types an integer which is not between 1 and 6, then your program must print an error message "Unknown
action!" to the user (hint: when testing the integer for the action, use the default case of a switch statement)
and then print the menu again (by just going back to the beginning of the while loop).
For example (where 7 is an input from the user):
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 7
Unknown action!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
If the user types something which is not an integer, the readPosInt method that you implemented in the previous
question will automatically repeat the menu and ask the user to type an integer again until the user actually types an
integer, so you do not have to worry about this in the code of the main method of your CLI class.
For example (where aaaa and bbbb cccc are inputs from the user):
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): aaaa
You must type an integer!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): bbbb cccc
You must type an integer!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
Here are the detailed explanations for each action.
Action 1: printing the total amount of debt.
When the user of the software specifies action 1, your program must simply print on the screen the total amount of debt
for all the payers of the finance office. Then your program goes back to printing the menu of actions (by just going back
to the beginning of the while loop).
For example (where 1 is an input from the user):
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 2000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
Action 2: adding a new payer to the finance office.
When the user of the software specifies action 2, your program must add a new payer to the finance office. To add a new
payer, your program needs to ask the user three things: the type of payer (an integer read using readPosInt: the integer
1 represents a student, the integer 2 represents an employee, the integer 3 represents a faculty member, and any other
integer must result in an error message "Unknown type of payer!" being printed and the software going
immediately back to the main menu), the name of the payer (a string read using readLine), and the initial amount of
money for the debt (for a student) or the salary (for an employee or a faculty member) when the payer is created. You
program must then create the correct payer, add it to the finance office, and print an information message for the user of
the software. The program then goes back to the menu. For example (where 1, 2, -100, 4, 2, 1, UIC Student, 5000, 1, 2, 2, Daniel, 1000, 1, 2, 3, Thompson, 2000, and
1 are inputs from the user):
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 0
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 2
Enter the payer type (student:1 employee:2 faculty member:3): -100
Positive integers only!
Enter the payer type (student:1 employee:2 faculty member:3): 4
Unknown type of payer!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 2
Enter the payer type (student:1 employee:2 faculty member:3): 1
Enter the name of the payer: UIC Student
Enter the initial amount of money: 5000
Student "UIC Student" with 5000 yuans of debt added
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 5000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 2
Enter the payer type (student:1 employee:2 faculty member:3): 2
Enter the name of the payer: Daniel
Enter the initial amount of money: 1000
Employee "Daniel" with 1000 yuans of salary added
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 4000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 2
Enter the payer type (student:1 employee:2 faculty member:3): 3
Enter the name of the payer: Thompson
Enter the initial amount of money: 2000
Faculty member "Thompson" with 2000 yuans of salary added
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 2000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
Note that the readPosInt method prevents the initial amount of money from being negative, so the constructor for
the Employee class will never throw a NegativeSalaryException when you create an employee object.
Nevertheless the code of the main method of your CLI class must handle this exception correctly by printing the error
message "BUG! This must never happen!" and immediately terminating the program using System.exit(1).
The same applies to a faculty member.
Action 3: listing the amount of debt for a given payer.
When the user of the software specifies action 3, your program must ask the user to type the name of a payer, and the
program then prints the amount of debt for this payer.
For example (where 3, UIC Student, 3, Daniel, 3, and Thompson are inputs from the user):
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: UIC Student
UIC Student has 5000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Daniel
Daniel has -1000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Thompson
Thompson has -2000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
If the name of the payer is wrong (the finance office does not have a payer with this name) then an
UnknownPayerException will be thrown by the FinanceOffice object. The code of the main method of your CLI class must then catch this exception, print the error message from the exception object, and then it just goes back to
printing the menu of actions (by just going back to the beginning of the while loop).
For example (where 3 and aaaa are inputs from the user):
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: aaaa
Payer aaaa unknown
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
Action 4: paying money to a given payer.
When the user of the software specifies action 4, your program must ask the user to type the name of a payer and an
amount of money, and the program then uses that amount of money to call the pay method of the payer with that name.
Then the program goes back to the main menu.
For example:
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: UIC Student
UIC Student has 5000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 4
Enter the name of the payer: UIC Student
Enter the amount of money: 1000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: UIC Student
UIC Student has 4000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Daniel
Daniel has -1000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 4
Enter the name of the payer: Daniel
Enter the amount of money: -500
Positive integers only!
Enter the amount of money: 500
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Daniel
Daniel has -500 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Thompson
Thompson has -2000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 4
Enter the name of the payer: Thompson
Enter the amount of money: 500
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Thompson
Thompson has -1500 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
If the name of the payer is wrong (the finance office does not have a payer with this name) then an
UnknownPayerException will be thrown by the FinanceOffice object. The code of the main method of your
CLI class must then catch this exception, print the error message from the exception object, and then it just goes back to
printing the menu of actions (by just going back to the beginning of the while loop).
For example:
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 4
Enter the name of the payer: aaaa
Enter the amount of money: 1000
Payer aaaa unknown Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
If a payer is an employee and the amount of money typed by the user is too big then a NegativeSalaryException
will be thrown by the Employee object. The code of the main method of your CLI class must then catch this exception,
print the error message from the exception object, and then it just goes back to printing the menu of actions (by just going
back to the beginning of the while loop).
For example:
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Daniel
Daniel has -500 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 4
Enter the name of the payer: Daniel
Enter the amount of money: 1500
An employee cannot be overpaid by 1000 yuans!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Daniel
Daniel has -500 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: UIC Student
UIC Student has 4000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 4
Enter the name of the payer: UIC Student
Enter the amount of money: 5000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: UIC Student
UIC Student has -1000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Thompson
Thompson has -1500 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 4
Enter the name of the payer: Thompson
Enter the amount of money: 2000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Thompson
Thompson has 500 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
Action 5: taking money from a given payer.
When the user of the software specifies action 5, your program must ask the user to type the name of a payer and an
amount of money, and the program then uses that amount of money, makes it negative, and pays that negative amount
to the payer with that name. Then the program goes back to the main menu.
For example:
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: UIC Student
UIC Student has 4000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 5
Enter the name of the payer: UIC Student
Enter the amount of money: 1000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: UIC Student
UIC Student has 5000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Daniel
Daniel has -500 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 5
Enter the name of the payer: Daniel Enter the amount of money: -500
Positive integers only!
Enter the amount of money: 500
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Daniel
Daniel has -1000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Thompson
Thompson has -1500 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 5
Enter the name of the payer: Thompson
Enter the amount of money: 500
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Thompson
Thompson has -2000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
If the name of the payer is wrong (the finance office does not have a payer with this name) then an
UnknownPayerException will be thrown by the FinanceOffice object. The code of the main method of your
CLI class must then catch this exception, print the error message from the exception object, and then it just goes back to
printing the menu of actions (by just going back to the beginning of the while loop).
For example:
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 5
Enter the name of the payer: aaaa
Enter the amount of money: 1000
Payer aaaa unknown
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6):
Note that, even if a payer is an employee, the readPosInt method prevents the amount of money typed by the user
from being negative. This means an employee will never throw a NegativeSalaryException. Nevertheless the code
of the main method of your CLI class must handle this exception by printing the error message "BUG! This must
never happen!" and immediately terminating the program using System.exit(1).
Action 6: quitting the program.
When the user of the software specifies action 6, your program must print a "Goodbye!" message, and terminate the
program using: System.exit(0).
For example (where 6 is an input from the user):
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 6
Goodbye!
Here is a more complete example of running the software:
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): aaaa
You must type an integer!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): bbbb cccc
You must type an integer!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): -100
Positive integers only!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 7
Unknown action!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 0
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 2
Enter the payer type (student:1 employee:2 faculty member:3): -100
Positive integers only! Enter the payer type (student:1 employee:2 faculty member:3): 4
Unknown type of payer!
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 2
Enter the payer type (student:1 employee:2 faculty member:3): 1
Enter the name of the payer: UIC Student
Enter the initial amount of money: 5000
Student "UIC Student" with 5000 yuans of debt added
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 5000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 2
Enter the payer type (student:1 employee:2 faculty member:3): 2
Enter the name of the payer: Daniel
Enter the initial amount of money: 1000
Employee "Daniel" with 1000 yuans of salary added
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 4000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 2
Enter the payer type (student:1 employee:2 faculty member:3): 3
Enter the name of the payer: Thompson
Enter the initial amount of money: 2000
Faculty member "Thompson" with 2000 yuans of salary added
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 1
Total amount of debt: 2000
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: UIC Student
UIC Student has 5000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Daniel
Daniel has -1000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: Thompson
Thompson has -2000 yuans of debt
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 3
Enter the name of the payer: aaaa
Payer aaaa unknown
Type an action (total:1 add:2 get:3 give:4 take:5 quit:6): 4
Enter the name of the payer: UIC Student
Enter the amount of