1. Which of the following are not valid Java identifiers, and why?
(a) wolVes
(b) United(there is only one)
(c) _87
(d) 5_3
(e) Real ale
(f) isFound?by
2. A class Television has the following fields:
private TelevisionManufacturer supplier; private String code
private int screenSize; // in inches private String type; // e.g. plasma screen
Assume that the class TelevisionManufacturer is available and that this class contains an equals method.
(a) Define a class variable, totalTVs, whose purpose is to keep track of the total number of Television objects constructed during execution of a program that uses the Television class.
(b) Declare a default constructor for this class.
(c) Declare a constructor for this class which has a formal parameter corresponding to each field.
(d) Declare an accessor method called getScreenSize whose purpose is to return the value of the screenSize field of this Television.
(e) Declare a mutator method that sets the type of this Television to a given value.
(f) Declare a method to determine whether or not this Television has been supplied by a given manufacturer.
Lab work
1. Consider the following algorithm.
(1) Randomly select a 4-digit positive number excluding 1111, 2222, ..., 9999, with leading zeros if necessary
// thus 158 would be represented by 0158 and
// 9 would be represented by 0009
(2) Let bigger denote the number obtained by taking the four digits obtained in step (1) in decreasing
order
(3) Let smaller denote the number obtained by taking the four digits obtained in step (1) in increasing order
(4) Obtain a new 4-digit number by subtracting smaller from bigger, inserting leading zeros if necessary
// e.g. 7666 - 6667 = 999, so the 4-digit value is 0999
(5) Repeat from step (2) for a maximum of 10 iterations or until two successive 4-digit numbers are identical, whichever occurs first.
Implement and test this algorithm in Java, using the Random class to generate test values.
2. This exercise is concerned with simulating the activity of a library with respect to its book-stock. You are required to write a Java application which contains a class called LibraryBook together with a main method class called LibrarySimulation.
The data about each LibraryBook consists of:
• author(s) (e.g. Lewis and Loftus)
• title (e.g. Java Software Solutions)
• number of pages (e.g. 832)
• library classification (e.g QA98 )
• number of times borrowed (e.g 53)
• current status
• number of pending reservations (may not exceed 3)
Once it has been initially set, the current status of a LibraryBook is one of the following:
REFERENCE ONLY, ON LOAN, AVAILABLE FOR LENDING
If the status of a LibraryBook is initially set to REFERENCE ONLY, its status will not change throughout the simulation.
If a LibraryBook is currently on-loan, a reservation may be placed on that LibraryBook but only up to a maximum of three pending reservations.
(a) Define an enum type in the LibraryBook class corresponding to the status list given above.
(b) Define the fields for the LibraryBook class corresponding to the data items given above.
(c) Define a class (static) variable to keep track of the total number of LibraryBooks cur- rently on loan.
(d) Define a single constructor with the following header:/**
* Constructor with arguments for a LibraryBook's author(s),
* title and number of pages
* @param bookAuthor the names of the author(s) of this LibraryBook
*
* @param bookTitle the title of this LibraryBook
* @param bookPages the number of pages of this LibraryBook
*
*/
public LibraryBook(String bookAuthor,
String bookTitle, int bookPages)
The instance variable for any field for which there is no corresponding formal parameter should be initialised to 0 (for primitive variables) and to null (for reference variables).
(e) Define all of the following public methods:
• methods for "getting" the author(s), the title, the number of pages, the library classification and the number of times borrowed for a
LibraryBook;
• a method with the following header for "setting" the library classification of a LibraryBook:
/**
* A method to reset the Library classification of this
* LibraryBook
* @param bookClass the proposed new classification
* @return true, if the proposed new
* classification has at
* least 3 characters to which
* the Library classification is
* reset.
* false, otherwise.
*/
public boolean setClassification(String bookClass)
• a method, setAsReferenceOnly, to designate a LibraryBook which has not already been designated as either reference-only or as available for lending, as reference- only;
• a method, setAsForLending, to designate a LibraryBook which has not already been designated as either reference-only or as available for lending, as available for lending;
• a boolean method isAvailable to determine whether or not this LibraryBook is available for lending;
• a method with the following header for reserving this LibraryBook, if possible:
/**
* If possible, reserves this LibraryBook.
* This is only possible if this LibraryBook is currently on loan
* and less than 3 reservations have been placed since this went
* on loan.
* @return true, if a new reservation has been made for this.
* false, otherwise
*/
public boolean reserveBook()
• a method, borrowBook, to simulate this LibraryBook being issued out to a bor- rower;
• a method, returnBook, to simulate the return of this LibraryBook by a borrower;
• a to String method that returns a description of a LibraryBook such that the output obtained when the statement System.out.println(courseText); is executed looks something like:
Title: Java Software Solutions Author: Lewis and Loftus Pages: 832
Classification: QA99
Include the following static method in your LibrarySimulation class:
/**
* A method to generate a collection of LibraryBook objects to use as
* test data in your simulation
* @return an array of LibraryBook objects
*
*/
public static LibraryBook [] generateBookStock(){ String [] authorsList =
{ "Lewis and Loftus", "Mitrani", "Goodrich", "Lippman", "Gross", "Baase", "Maclane", "Dahlquist", "Stimson", "Knuth", "Hahn", "Cormen and Leiserson", "Menzes", "Garey and Johnson"};
String [] titlesList =
{ "Java Software Solutions", "Simulation",
"Data Structures", "C++ Primer", "Graph Theory", "Computer Algorithms", "Algebra", "Numerical Methods", "Cryptography","Semi-Numerical Algorithms",
"Essential MATLAB", "Introduction to Algorithms", "Handbook of Applied Cryptography",
"Computers and Intractability"};
int [] pagesList = {832, 185, 695, 614, 586, 685, 590, 573, 475,
685, 301, 1175, 820, 338};
int n = authorsList.length;
LibraryBook [] bookStock = new LibraryBook[n]; for(int i = 0; i < n; i++){
bookStock[i] = new LibraryBook(authorsList[i],
titlesList[i], pagesList[i]);
}
// set library classification for half of the LibraryBooks for(int i = 0; i < n; i=i+2){
bookStock[i].setClassification("QA" + (99 - i));
}
// set approx. two thirds of LIbraryBooks in test data as
// lending books
for(int i = 0; i < 2*n/3; i++) bookStock[i].setAsForLending();
// set approx. one third of LibraryBooks in test data as
// reference-only
for(int i = 2*n/3; i < n; i++) bookStock[i].setAsReferenceOnly();
return bookStock;
}
(f) Define a third static method in your LibrarySimulation class, with the following header:
/**
* @param bookStock the stock of LibraryBooks in the library
* @param numberOFevents the size of the events table to be
* @return generated table of events generated during
* the simulation
*/
public static String [] runSimulation(LibraryBook [] bookStock,
int numberOFevents,)
This static method is to implement an algorithm for simulating the activity of the library with respect to its book-stock. The algorithm generates a sequence of random events. Each succes- sive event is determined by the current status of a randomly selected LibraryBook. At each stage in this process, each LibraryBook is equally-likely to be selected. There are six types of event:
• the selected library book is currently unclassified and is now given its proper classification (BOOK IS CLASSIFIED);
• the selected library book is already classified but is reference-only and is therefore not available for lending (REFERENCE ONLY BOOK);
• the selected library book is classified and available for lending and is now loaned out (BOOK IS LOANED OUT);
• the selected library book is currently on-loan and is being returned to the Library (BOOK IS RETURNED);
• the selected library book is currently on-loan and a reservation is placed on that book (RESERVATION PLACED FOR ON-LOAN BOOK);
• the selected library book is currently on-loan but further reservations are not allowed on that book (BOOK IS ON-LOAN BUT CANNOT BE RESERVED).
A maximum of three reservations may be placed on an on-loan LibraryBook. When a LibraryBook that has been on-loan is returned, if it has at least one reservation placed on it, then the LibraryBook remains on-loan, but with the number of reservations placed on it reduced by 1.
As can be seen from the above list of possible events, when the simulation leads to the selection of an on-loan LibraryBook, there are two possible situations: either the LibraryBook is being returned or an attempt is being made to place a reservation on the LibraryBook. Your algorithm should randomly choose between these situations (hint: generate a random integer in the range {0, 1} with 0 corresponding to a return and 1 to an attempted reservation).
The output from the runSimulation method is an array, each element of which is an event summary and has the form:
:
A pseudo-code high-level description of the algorithm that runSimulation should imple- ment is given below:
let n = number of library books in library book-stock;
// assume we have library book 0 to library book (n-1) initialise events list;
for each event number from 1 to the required number of events do select a library book at random from the book-stock;
// i.e. generate a random number from 0 .. (n-1)
Use the status of the selected library book to determine the type of event and process that event; add the event summary to the events list endfor
The print-out of the events list from a typical run of your program might look like: run:
0 0 --- BOOK IS CLASSIFIED
1 0 QA97 BOOK IS LOANED OUT
2 1 QA95 BOOK IS LOANED OUT
3 2 QA99 BOOK IS LOANED OUT
4 3 QA93 REFERENCE ONLY BOOK
5 3 QA95 BOOK IS RETURNED
6 2 QA95 BOOK IS LOANED OUT
7 3 QA97 BOOK IS RETURNED
8 2 --- BOOK IS CLASSIFIED
9 2 QA99 BOOK IS RETURNED
10 1 QA98 BOOK IS LOANED OUT
11 2 QA95 BOOK IS RETURNED
12 1 QA93 REFERENCE ONLY BOOK
13 1 QA98 BOOK IS RETURNED
14 0 QA93 REFERENCE ONLY BOOK
15 0 QA98 BOOK IS LOANED OUT