Project Requirements
Create a new Eclipse workspace named "Project_1234567890" on the desktop of your computer (replace 1234567890 with your student ID number). For each question below, create a new project in that workspace. Call each project by its question number: "Question1", "Question2", etc. If you do not remember how to create a workspace or projects, read the "Introduction to Eclipse" document. Answer all the questions below. At the end of the project, create a ZIP archive of the whole workspace folder. The resulting ZIP file must be called "Project_1234567890.zip" (replace 1234567890 with your student ID number).
Here are a few extra instructions:
- Give meaningful names to your variables so we can easily know what each variable is used for in your program.
- Put comments in your code (in English!) to explain WHAT your code is doing and also to explain HOW your program is doing it. Also put comments in your tests.
- Make sure all your code is properly indented (formatted). Your code should be beautiful to read. Failure to follow these instructions will result in you losing points.
In this project you need to write a book lending system for a Library. The system has different roles for registered users. There are two types of user roles: borrower and lender.
Write an IUser interface for library users, with the following UML specification:
+ +
| <
| IUser |
+ +
| + getName(): String |
| + getBook(): int |
| + moreBook(int number): void |
+ +
and a User class that implements IUser and has the following UML specification:
+ +
| User |
+ +
| - name: String |
| - book: int |
|
+ +
The name instance variable indicates the user name. The book instance variable indicates the number of books
borrowed by the user.
The setBook method changes the number of books borrowed by the user. The setBook method is protected, not public. This means that only subclasses of the User class can use the setBook method. All the other classes in the system cannot use the setBook method, so they cannot change the number of books borrowed by a user.
The purpose of the moreBook method is to increase the number of books borrowed or lent by the user (depending on what kind of user it is) by the number given as argument to the method. The moreBook method of the User class is abstract, since we do not know what kind of role the user is (a borrower borrows books from other users and a lender lend books to other users).
Also add to your program a Test class to test your User class.
public class Test {
public static void main(String[] args) { User.testUser();
}
}
Question 2Add a class Lender that extends User. The constructor of the Lender class takes as arguments a name and the number of books lent by the user. The Lender class does not have any instance variable.
Warning: the constructor of the Lender class takes as argument the number of books lent by the lender, but the book instance variable of the User class indicates how many books the user borrowed! Lending books is the same as borrowing a negative number of books.
The moreBook method of the Lender class increases the number of books lent by the lender user by the number given as argument to the method (so the books borrowed by the lender becomes more negative!)
Make sure you test all the methods of your new Lender class using testLender method. Here are some tests for your new Lender class:
public static void testLender()
{
Lender l = new Lender("Anna",5); System.out.println(l.getName() == "Anna"); System.out.println(l.getBook() == -5); l.setBook(-6); System.out.println(l.getBook() == -6); l.moreBook(2); System.out.println(l.getBook() == -8); l.moreBook(-9); System.out.println(l.getBook() == 1);
}
Also, do not forget to modify your Test class to test the Lender class.
Question 3Add a class Borrower that extends User. The constructor of the Borrower class takes a name and a number of books borrowed by the borrower. If the number of books given as argument is strictly less than zero, then the constructor must throw a NotALenderException with the message "A new borrower cannot lend books.". The borrower class does not have any instance variable.
The moreBook method of the Borrower class increases the number of books borrowed by the borrower by the number of books given as argument to the method (so the books borrowed by the borrower becomes more positive!)
For example, if a borrower currently borrows 10 books and moreBook(2) is called then the borrower borrows 12 books. It is fine for the moreBook method to be given a negative value as argument, which means the borrower then just returned some books. For example, if a borrower currently borrows 10 books and moreBook(-2) is called then the borrower borrows 8 books.
However, a borrower cannot lend books, so the number of books borrowed by the borrower must always be positive or zero, never negative. If the argument given to the moreBook method is too negative and would change the book variable into a negative value, then the number of books borrowed by the borrower must not change and the moreBook method must throw a NotALenderException with the message “A borrower cannot lend XXX book(s).”, where XXX is replaced with the result of -(book + number).
For example, if a borrower currently borrows 10 books and moreBook(-12) is called then the borrower still borrows 10 books and the method throws a NotALenderException with the message “A borrower cannot lend 2 book(s).”.
Note: to simplify the project, do not worry about the setBook method. Change other classes and interfaces as necessary.
Make sure you test your new Borrower class, including inherited methods. Here are some tests for your new
Borrower class:
public static void testBorrower()
{
try
{
Borrower b = new Borrower("Bob",-1);
books."));
} catch(NotALenderException e)
{
System.out.println(e.getMessage().equals("A new borrower cannot lend
}
try
{
Borrower b = new Borrower("Bob",10); System.out.println(b.getName()=="Bob"); System.out.println(b.getBook()==10); b.setBook(5); System.out.println(b.getBook()==5); b.moreBook(2); System.out.println(b.getBook()==7); b.moreBook(-2); System.out.println(b.getBook()==5); b.moreBook(-5); System.out.println(b.getBook()==0); b.moreBook(-1);
} catch(NotALenderException e)
{
System.out.println(e.getMessage().equals("A borrower cannot lend 1 book(s)."));
}
}
Also, do not forget to modify your Test class to test the Borrower class.
Question 4Add a Library class with the following UML specification:
+ +
| Library |
+ +
| - name: String |
| - users: ArrayList
+ +
| + Library(String name) |
| + addUser(IUser user): void |
| + totalBorrowedBooks(): int |
| + getBook(String name): int |
| + moreBook(String name, int number): void |
| + testLibrary(): void |
+ +
When a library is created, it has an arraylist of users (IUser) but the arraylist is empty (the arraylist does not contain any user).
The addUser method takes a user (IUser) as argument and adds the user to the arraylist of users for the library.
The totalBorrowedBooks method returns as result the total number of books borrowed by all users of the library (the result can be either positive or negative).
The getBook method takes as argument the name of a user and returns as result the number of books currently borrowed by the user. If the library does not have a user with the given name, then the getBook method must throw an UnknownUserException with the message "User XXX unknown.", where XXX is replaced with the name of the user. Do not worry about multiple users having the same name. You can assume all user names are unique in the arraylist.
The moreBook method takes as argument the name of a user and a number of books and changes the number of books currently borrowed by that user. If the library does not have a user with the given name, then the moreBook method must throw an UnknownUserException with the message "User XXX unknown.", where XXX is replaced with the name of the user. Do not worry about multiple users having the same name.
Note: the moreBook method does not catch any exception, it only throws exceptions.
Hint: use the equals method to compare strings, not the == operator which only works with constant strings. Make sure you test your new Library class in testLibrary method. Here are some tests for your new Library
class:
public static void testLibrary() {
Library li = new Library("UIC Library");
System.out.println(li.totalBorrowedBooks() == 0);
li.addUser(new Lender("L1", 10)); try {
System.out.println(li.getBook("L1") == -10);
System.out.println(li.totalBorrowedBooks() == -10);
li.addUser(new Borrower("B1", 20));
System.out.println(li.getBook("L1") == -10);
System.out.println(li.getBook("B1") == 20);
System.out.println(li.totalBorrowedBooks() == 10); li.getBook("B2");
} catch(UnknownUserException ex) { System.out.println(ex.getMessage().equals("User B2 unknown."));
} catch(NotALenderException ex) {
// This should never happen! System.out.println(false);
}
//More test cases are needed…
……
……
……
}
Also, do not forget to modify your Test class to test the Library class.
Question 5In this question and the next one we want to create a command line interface (CLI) for our Library book lending system.
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 system 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 6Once 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 Library object with the name "UIC Library". The main method of the CLI class must then print a menu that allows the user of your system to do six different actions that involve the library 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 about 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 more:4 less: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 more:4 less: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 library 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 more:4 less:5 quit:6): 7 Unknown action!
Type an action (total:1 add:2 get:3 more:4 less: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 are inputs from the user):
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): aaaa You must type an integer!
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): bbbb You must type an integer!
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6):
Here are the detailed explanations for each action.
Action 1: printing the total number of books borrowed by all users.When the user of the system specifies action 1, your program must simply print on the screen the total number of books currently borrowed by all users of the library. 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 more:4 less:5 quit:6): 1 Total number of borrowed books: 50
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6):
Action 2: adding a new user to the library.When the user of the software specifies action 2, your program must add a new user to the library. To add a new user, your program needs to ask the user three things: the role of user (an integer read using readPosInt: the integer 1 represents lender, the integer 2 represents borrower, any other integer must result in an error message "Unknown
user role!" being printed and the software going immediately back to the main menu), the name of the user (a string read using readLine), and the initial number of books that the user lends (for a lender) or borrows (for a borrower). You program must then create the correct user, add it to the library, and print an information message. The program then goes back to the menu.
For example (where 2, 3, 2, 1, Anna, 5, 2, 2, Bob, and 10 are inputs from the user):
| Type an action (total:1 add:2 get:3 more:4 less:5 | quit:6): | 2 |
| Type the user role (lender:1 borrower:2): 3 | ||
| Unknown user role! | ||
| Type an action (total:1 add:2 get:3 more:4 less:5 | quit:6): | 2 |
| Type the user role (lender:1 borrower:2): 1 | ||
| Enter the name of the user: Anna | ||
| Enter the initial number of borrowed books: 5 | ||
| Lender "Anna" lending 5 book(s) has been added. | ||
| Type an action (total:1 add:2 get:3 more:4 less:5 | quit:6): | 2 |
| Type the user role (lender:1 borrower:2): 2 |
Enter the name of the user: Bob
Enter the initial number of borrowed books: 10 Borrower "Bob" borrowing 10 book(s) has been added.
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6):
Note that the readPosInt method prevents the initial number of books from being negative, so the constructor for the Borrower class will never throw a NotALenderException when you create a borrower object. 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 3: get the number of books borrowed by a given user.When the user of the system specifies action 3, your program must ask the user to type the name of a user, and the program then prints the number of books which is currently borrowed by this user.
For example (where 3, Anna, 3, and Bob are inputs from the user):
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Anna
Anna borrows -5 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Bob
Bob borrows 10 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6):
If the name of the user is wrong, then an UnknownUserException exception will be thrown by the Library object. The code of the main method of your CLI class must 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 more:4 less:5 quit:6): 3 Enter the name of the user: aaaa
User aaaa unknown.
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6):
Action 4: increasing the number of books of a given user.When the user of the software specifies action 4, your program must ask the user to type the name of a user, and a number of books, and the program then uses that number to increase the number of books lent or borrowed by the user. Then the program goes back to the main menu.
For example:
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Anna
Anna borrows -5 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 4 Enter the name of the user: Anna
Enter the number of books: 2
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Anna
Anna borrows -7 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Bob
Bob borrows 10 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 4 Enter the name of the user: Bob
Enter the number of books: 2
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Bob
Bob borrows 12 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6):
If the name of the user is wrong, then an UnknownUserException exception will be thrown by the Library object. The code of the main method of your CLI class must 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 4, aaaa, and 2 are inputs from the user):
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 4 Enter the name of the user: aaaa
Enter the number of books: 2 User aaaa unknown.
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6):
Note that, even if a consumer is a borrower, the readPosInt method prevents the typed number of books from being negative. This means a borrower will never throw a NotALenderException. 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).
For example (where 3, Bob, 4, Bob, and -15 are inputs from the user):
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Bob
Bob borrows 12 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 4 Enter the name of the user: Bob
Enter the number of books: -15 Positive integers only!
Enter the number of books:
Action 5: decreasing the number of books of a given user.When the user of the software specifies action 5, your program must ask the user to type the name of a user, and a number of books, and the program then uses that number to decrease the number of books lent or borrowed by the user. Then the program goes back to the main menu.
Note: the library object that you are using does not have a method to decrease books. So, in the code of the main method of the CLI class, simulate decreasing books by simply increasing books by a negative number! For example, decreasing the number of books of a user by 5 books is the same as increasing the number of books by -5 books.
For example:
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3
Enter the name of the user: Anna Anna borrows -7 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 5 Enter the name of the user: Anna
Enter the number of books: 6
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Anna
Anna borrows -1 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Bob
Bob borrows 12 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 5 Enter the name of the user: Bob
Enter the number of books: 5
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Bob
Bob borrows 7 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6):
If the name of the user is wrong, then an UnknownUserException exception will be thrown by the Library object. The code of the main method of your CLI class must 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 5, aaaa, and 2 are inputs from the user):
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 5 Enter the name of the user: aaaa
Enter the number of books: 2 User aaaa unknown.
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6):
If a consumer is a borrower and the number of books typed by the user is too big, then a NotALenderException exception will be thrown by the Borrower object. The code of the main method of your CLI class must 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, Bob, 5, Bob, 10are inputs from the user):
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Bob
Bob borrows 7 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 5 Enter the name of the user: Bob
Enter the number of books: 10
A borrower cannot lend 3 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Bob
Bob borrows 7 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6):
Action 6: quitting the program.When the user of the system 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 more:4 less:5 quit:6): 6 Goodbye!
Here is a more complete example of running the system:
| Type an action (total:1 add:2 | get:3 | more:4 | less:5 | quit:6): | aaaa |
| You must type an integer! Type an action (total:1 add:2 | get:3 | more:4 | less:5 | quit:6): | -100 |
| Positive integers only! Type an action (total:1 add:2 | get:3 | more:4 | less:5 | quit:6): | 7 |
| Unknown action! Type an action (total:1 add:2 | get:3 | more:4 | less:5 | quit:6): | 1 |
| Total number of borrowed books: 0 Type an action (total:1 add:2 get:3 | more:4 | less:5 | quit:6): | 2 | |
Type the user role (lender:1 borrower:2): 0 Unknown user role!
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 2 Type the user role (lender:1 borrower:2): 3
Unknown user role!
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 2 Type the user role (lender:1 borrower:2): 1
Enter the name of the user: Anna
Enter the initial number of borrowed books: 5 Lender "Anna" lending 5 book(s) has been added.
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 2 Type the user role (lender:1 borrower:2): 2
Enter the name of the user: Bob
Enter the initial number of borrowed books: 10 Borrower "Bob" borrowing 10 book(s) has been added.
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 1 Total number of borrowed books: 5
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Anna
Anna borrows -5 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Bob
Bob borrows 10 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: aaaa
User aaaa unknown.
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 4 Enter the name of the user: Anna
Enter the number of books: 2
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Anna
Anna borrows -7 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Bob
Bob borrows 10 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 4 Enter the name of the user: Bob
Enter the number of books: 2
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Bob
Bob borrows 12 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Anna
Anna borrows -7 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 5 Enter the name of the user: Anna
Enter the number of books: 6
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Anna
Anna borrows -1 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Bob
Bob borrows 12 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 5 Enter the name of the user: Bob
Enter the number of books: 5
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Bob
Bob borrows 7 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 5 Enter the name of the user: Bob
Enter the number of books: 10
A borrower cannot lend 3 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 3 Enter the name of the user: Bob
Bob borrows 7 book(s).
Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): 6 Goodbye!
Question 7We now want to create a graphical user interface (GUI) for our library book lending system. Since we want the system to have multiple views, we will use the Model-View-Controller design pattern.
First, create a ModelListener interface with the following UML specification:
+ +
| <
| ModelListener |
+ +
| + update(): void |
+ +
This interface will be implemented by views and the model will use this interface to notify the views that they need to update themselves.
Second, the Library class is the class that contains all the data for the library. Therefore the Library class plays the role of the model. Therefore the Library class needs to keep an arraylist of model listeners that need to be notified every time the library (the model) changes.
- Add to the Library class an private instance variable, an arraylist of ModelListener. When a library is created, it has an empty arraylist of listeners.
- Also add to the Library class an addListener method that takes a ModelListener as argument and adds it to the arraylist of listeners.
- Also add to the Library class a private notifyListeners method that takes nothing as argument and calls the update method of all the listeners of the library.
- Then change the addUser and moreBook methods so that they call the notifyListeners every time a change is made to the library's data (only the addUser and moreBook methods change the library’s data, so only these two methods need to call the notifyListeners method; the totalBorrowedBooks and getBook methods do not change the library’s data, they only inspect the data, so they do not need to call the notifyListeners method).
Use the Test class to make sure all your tests still work. Use the CLI class to make sure your command line interface still works.
Third, create a ViewSimple class that extends JFrame, implements the ModelListener interface, and has the following UML specification:
+ +
| ViewSimple |
+ +
| - m: Library |
| - c: ControllerSimple |
| - label: JLabel |
+ +
| + ViewSimple(Library m, ControllerSimple c) |
| + update(): void |
+ +
The constructor of the ViewSimple class registers the view with the model (the library) using the addListener method of the model, creates a JLabel object, stores it in the label instance variable of the ViewSimple class, initializes it to display the total number of books borrowed by all users of the library, and adds the label to the view (which is a frame). The update method of the ViewSimple class updates the text of the label as necessary so that the label always displays the current value of the total number of books borrowed by all users of the library.
Fourth, create a ControllerSimple class with the following UML specification:
+ +
| ControllerSimple |
+ +
| - m: Library |
+ +
| + ControllerSimple(Library m) |
+ +
Since the ViewSimple does not have any button, it cannot perform any action, therefore the corresponding controller ControllerSimple does nothing. (We still want to have the ControllerSimple class so that our application follows the correct Model-View-Controller design pattern.)
Fifth, create a GUI class with a main method. In this main method, create an anonymous class that implements the Runnable interface with a run method and use the javax.swing.SwingUtilities.invokeLater method to run that code on the event dispatch thread.
Sixth, we need to connect the model, the view, and the controller to each other. So in the run method of the anonymous class:
- create a Library object (the model object) with the name "UIC Library";
- then create a ControllerSimple object (the controller object) that takes the model object as argument;
- then create a ViewSimple object that takes the model object and the controller object as argument;
Use the GUI class to run your GUI: you should see a window that shows the total number of books borrowed by all users of the library. This total number must be zero, since the library (model object) you just created above does not contain any user!
As a test, in the run method of the anonymous class, you can try to manually add to your library (model object) some lenders and borrowers to check that whether your GUI displays the correct the total number of books borrowed by all users in the library.
For example, if we add a lender who has borrowed -5 books and a borrower who has borrowed 10 books, the GUI class running result is shown in the following figure:
Question 8In the next questions we want to add more views. So, to simplify the next questions, create a View class which is going to be the superclass of all views. This View class is generic, extends JFrame, implements the ModelListener interface, and has the following UML specification:
+ +
| View
+ +
| # m: Library |
| # c: T |
+ +
| + View(Library m, T c) |
| + update(): void |
+ +
The m and c instance variables of the View class are protected (so that they can be easily used in all the subclasses of View). In the constructor of the View class, the view registers itself with the model. The update method of the View class is abstract.
Then modify the ViewSimple class to be a subclass of the View
Also create a Controller class which is going to be the superclass of all controllers. This Controller class has the following UML specification:
+ +
| Controller |
+ +
| # m: Library |
+ +
| + Controller(Library m) |
+ +
The m instance variable of the Controller class is protected (so that it can be easily used in all the subclasses of
Controller).
Then modify the ControllerSimple class to be a subclass of the Controller class. (Note: since ControllerSimple does nothing anyway, we could just remove it and replace it with Controller in the definition of ViewSimple and in the run method of the GUI class, but here we keep ControllerSimple just to make the Model-View-Controller design pattern very clear.)
Run your GUI and check that it still works as before.
Question 9We now want to add a new “get book” view that allows the user of the system to check how many books a specific user is borrowing.
Create a ViewGetBook class that extends View
+ +
| ViewGetBook |
+ +
| - t: JTextField |
+ +
| + ViewGetBook(Library m, ControllerGetBook c) |
| + update(): void |
+ +
The ViewGetBook shows the text field called t (where the user can type text) and a button. Use a grid layout manager to position the two components. For example:
The user can type in the text field t the name of a library user. For example:
When the user then clicks on the button, the action listener of the button must read the name of the library user that was typed in the text field (using the getText method of the text field) and must call the getBook method of the controller with that user name as argument. The getBook method of the controller returns a string as result which must then be displayed back to the user using a message dialog (using the showMessageDialog method of the JOptionPane class). For example:
The update method of the ViewGetBook class does nothing, because the ViewGetBook class does not graphically display any data from the library (the model).
Also create a ControllerGetBook class that extends Controller and has the following UML specification:
+ +
| ControllerGetBook |
+ +
+ +
| + ControllerGetBook (Library m) |
| + getBook(String name): String |
+ +
The getBook method takes the name of a user as argument. The getBook method of the controller then calls the getBook method of the library to get the number of books currently borrowed by that user. The getBook method of the controller then transforms the integer result of the getBook method of the library into a string and returns that string as result (to the view). If the getBook method of the library throws an UnknownUserException then the getBook method of the controller must catch this exception and return as result the error message from the exception object.
Modify the run method of the GUI class to add a ViewGetBook view that uses a ControllerGetBook
controller and the same model as before (not a new model!) Do not delete the previous view.
Run your GUI and check that you can correctly use the new view to query the number of books borrowed by different users of your library (obviously your library must have some users in it to test this: see the last paragraph of Question 7).
Also check that querying the number of books of an unknown user correctly shows an error message. For example:
We now want to add a new “more book” view that allows the user of the system to increase the number of book
borrowed or lent by the user (depending on what kind of user it is) of a specific user.
Create a ViewMoreBook class that extends View
+ +
| ViewMoreBook |
+ +
| - t1: JTextField |
| - t2: JTextField |
+ +
| + ViewMoreBook (Library m, ControllerMoreBook c) |
| + update(): void |
+ +
The ViewMoreBook shows the two text field called t1 and t2 (where the user can type text) and a button. Use a grid layout manager to position the three components. For example:
he user can type in the first text field the name of a library user and can type in the second text field a number of books. For example:
When the thethat was typed in the first text field (using the getText method of the text field) and the number of books that was typed in the second text field (using again the getText method) and must call the moreBook method of the controller with these two strings as arguments. The moreBook method of the controller then returns a string as result. If the string returned by the moreBook method of the controller is different from the empty string "" then this string must be displayed back to the user using a message dialog (using the showMessageDialog e class). If the string returned by the moreBook method of the controller is equal to the emptyeBook.
The update method of the ViewMoreBook class does nothing, because the ViewMoreBook class does not graphically display any data from the library (the model).
Also create a ControllerMoreBook class that extends Controller and has the following UML specification:
+ +
| ControllerMoreBook |
+ +
+ +
| + ControllerMoreBook(Library m) |
| + moreBook(String name, String number): String |
+ +
The moreBook method takes the name of a user and a number of books (as a string) as arguments. The moreBook method of the controller then transforms the number of books from a string to an integer (using the Integer.parseInt static method) and calls the moreBook method of the library to increase the number of books borrowed or lent by the user (depending on what kind of user it is) of a specific user, by the given argument.
- If no exception occurs then the moreBook method of the controller returns the empty string.
- If the moreBook method of the library throws an UnknownUserException then the moreBook method of the controller must catch this exception and return as result the error message from the exception object.
- If the moreBook method of the library throws a NotALenderException then the moreBook method of the controller must catch this exception and return as result the error message from the exception object.
- If the parseInt method of the Integer class throws a NumberFormatException (because the user typed something which is not an integer) then the moreBook method of the controller must catch this exception and return as result the error message from the exception object.
Note: to keep things simple, it is allowed for a user of your system to increase the number of books of a user by a negative number, so there is no need to check for that.
Modify the run method of the GUI class to add a ViewMoreBook view that uses a ControllerMoreBook
controller and the same model as before (not a new model!) Do not delete the previous views.
Run your GUI and check that you can correctly use the new view to increase the number of books for different users of your library (obviously your library must have some users in it to test this: see the last paragraph of Question 7).
- Check that, when you increase a user’s book, the simple view is automatically correctly updated to show the new total number of borrowed books for all users of the library.
- Also use the “get book” view to check that the user’s book value correctly changed.
- Also check that increasing the book number of an unknown user correctly shows an error message. For example:
- Also check that increasing the book of a user by a large negative number correctly shows an error message. For example:
- Also check that trying to increase the book of a user by a number which is not an integer correctly shows an error message (do not worry about the content of the error message). For example:
We now want to add a new “create” view that allows the user of the system to create a user for the library system. Create a ViewCreate class that extends View
+ +
| ViewCreate |
+ +
| - t1: JTextField |
| - t2: JTextField |
| - cb: JComboBox
+ +
| + ViewCreate(Library m, ControllerCreate c) |
| + update(): void |
+ +
The ViewCreate shows the two text field called t1 and t2 (where the user can type text), the combo box cb (where the user can select one option from a menu) and a button. Use a grid layout manager to position the four components. For example:
The user can type in the first text field the name of a new library user and can type in the second text field a number of books for the new library user. The combo box offers only two menu options: "Lender" and "Borrower". For example:
When the user then clicks on the button, the action listener of the button must read the name of the new library user that was typed in the first text field (using the getText method of the text field), read the number of books that was typed in the second text field (using again the getText method), and read which menu option was selected in the combo box (using the getSelectedIndex method of the combo box, which returns the integer 0 or 1 depending on which menu option the user selected in the combo box), and calls the create method of the controller with these two strings and the integer as arguments. The create method of the controller then returns a string as result. If the string returned by the create method of the controller is different from the empty string "" then this string must be displayed back to the user using a message dialog (using the showMessageDialog method of the JOptionPane class). If the string returned by the create method of the controller is equal to the empty string "" then nothing happens in ViewCreate.
The update method of the ViewCreate class does nothing, because the ViewCreate class does not graphically display any data from the library (the model).
Also create a ControllerCreate class that extends Controller and has the following UML specification:
+ +
| ControllerCreate |
+ +
+ +
| + ControllerCreate(Library m) |
| + create(String name, String number, int type): String |
+ +
The create method takes as arguments the name of a new library user, a number of books (as a string), and an integer representing the role of user to create (where the integer 0 means a lender and the integer 1 means a borrower). The create method of the controller then transforms the book number from a string to an integer (using
the Integer.parseInt static method), creates an object from the correct class (based on the role specified by the user input: lender or borrower) and calls the addUser method of the library to add the new user object to the library.
- If no exception occurs then the create method of the controller returns the empty string.
- If the constructor of the Borrower class throws a NotALenderException then the create method of the controller must catch this exception and return as result the error message from the exception object.
- If the parseInt method of the Integer class throws a NumberFormatException (because the user typed something which is not an integer) then the create method of the controller must catch this exception and return as result the error message from the exception object.
Modify the run method of the GUI class to add a ViewCreate view that uses a ControllerCreate controller and the same model as before (not a new model!) Do not delete the previous views.
Note: if at the end of Question 7 you had manually added to your library (model object) some users for testing, then you must now remove those users from the run method of the anonymous class inside the GUI class. You do not need these test users anymore because you have now a graphical user interface to create new users!
Run your GUI and check that you can correctly use the new view to create different users for your library, with different types of roles.
- Check that, when you create a new user, the simple view is automatically correctly updated to show the new total number of books borrowed by all users.
- Also use the “get book” view to check that the users are correctly created with the correct names and correct number of books.
- Also check that trying to create a borrower with a negative number of books correctly shows an error message. For example:
- Also check that trying to create a user with a number of books which is not an integer correctly shows an error message (do not worry about the content of the error message). For example:
- After you created a new user, you can also check whether it is a lender or a borrower using the “more book” view to increase the number of books of the user by a big negative number:
- if the new user you created is a lender, then increasing the number of books by a big negative value will work and the number of books borrowed by the user will just become a larger value (you can then check that using the “get book” view);
- if the new user you created is a lender, then increasing the number of books by a big negative value will fail with an error message and the number of books borrowed by the user will not change (you can then check that using the “get book” view).
We now want to add a new “history” view that allows the user of the system to keep track of how the total number of books borrowed by all users of the library changes over time.
Before we can add such a view to the GUI, first we need to change the model (the Library class) to keep track of how the total number of books borrowed by all users of the library changes over time. Therefore, in the Library class, add a new private instance variable called history which is an arraylist of integers. This arraylist must be initialized to contain only one value: zero (meaning that, when the library is created, it has no books being lent or borrowed).
We know that the data of the library can change only in two methods of the Library class: in the addUser method and in the moreBook method (this is why these two methods both call notifyListeners: to tell the views that data has changed and that the views must update themselves). Therefore, it is in these two methods that we must keep track of how the total number of books borrowed by all users of the library changes over time. Therefore, in these two methods, call the totalBorrowedBooks method and add the result to the history arraylist.
Note: in each of the two methods addUser and moreBook, you must call the totalBorrowedBooks method and add the result to the history arraylist before notifyListeners is called, otherwise the “history” view that you are going to create below will not show the correct results when it is notified by the library that it must update itself!
Also add to the Library class a getHistory method that returns as result the arraylist of integers which is the
library’s history.
Create a HistoryPanel class that extends JPanel. The constructor of HistoryPanel takes as argument a model object of type Library, which you need to store in some private instance variable.
Add to the HistoryPanel class two private methods called historyMax and historyMin that take an arraylist of integers as argument and return as result the maximum and minimum number in the arraylist, respectively (you can assume that the arraylist contains at least one number). Then add to the HistoryPanel class a private method called historyRange that takes an arraylist of integers as argument and returns as result the difference between
the max and min of the integers in the arraylist, or returns as result 10 if the difference between the man and min of the integers in the arraylist is strictly less than 10.
Override the protected void paintComponent(Graphics g) method inherited from JPanel, and, inside your new paintComponent method, draw graphically how the total number of books borrowed by all users of the library changes over time, as follows:
-
- Compute the following variables (where history is the result of calling the getHistory method of the model):
int min = historyMin(history);
int range = historyRange(history); int maxX = getWidth() - 1;
int maxY = getHeight() - 1;
int zero = maxY + min * maxY / range;
-
- Draw a blue line between the point (0, zero) and the point (maxX, zero) (this blue line then represents the horizontal “zero” axis).
- For each value v at index i in the history arraylist that you want to draw:
- Use x = 10 * i for the horizontal coordinate;
- Use y = zero - v * maxY / range for the vertical coordinate;
- Draw red lines between all the points (x, y) (if there is only one value in the arraylist then just draw a rectangle of size 1 by 1 at position (x, y)).
Create a ViewHistory class that extends View
+ +
| ViewHistory |
+ +
+ +
| + ViewHistory(Library m, ControllerHistory c)|
| + update(): void |
+ +
The ViewHistory shows only a HistoryPanel object, nothing else. The update method of the ViewHistory class calls Swing’s repaint method (this forces Swing to redraw everything every time the model changes, which in turn forces Swing to automatically call the paintComponent method of the HistoryPanel to redraw the updated version of the history).
Also create a ControllerHistory class that extends Controller and has the following UML specification:
+ +
| ControllerHistory |
+ +
+ +
| + ControllerHistory(Library m) |
+ +
Since the ViewHistory does not receive any input from the user, the ControllerHistory does nothing. (Note: since ControllerHistory does nothing anyway, we could just remove it and replace it with Controller in the definition of ViewHistory and in the run method of the GUI class, but here we keep ControllerHistory just to make the Model-View-Controller design pattern very clear.)
Modify the run method of the GUI class to add a ViewHistory view that uses a ControllerHistory controller and the same model as before (not a new model!) Do not delete the previous views.
Run your GUI and check that adding new users and changing the books borrowed by users correctly updates the graphical history of the library’s total number of borrowed books. For example, if the user of the system creates a
lender with 5 lent books, then create a borrower with 10 borrowed books, then increase the books of the lender by 2 books, increase the books of the borrower by 3 books and increase the books of the borrower by -5 books, the plotted history is shown as follows:
Check that all the other features of your system still work correctly. Also run your tests and the CLI to make sure everything still works correctly.
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