Description

Lab Rules

You may work individually or with one partner in lab. We suggest that you have a TA evaluate your progress on each milestone before you move onto the next. The labs are designed to be completable by the end of lab. If you are unable to complete all of the milestones by the end of lab, you have until the last office hours on Monday to get those checked off by any of the course TAs. We suggest you get your milestones checked off as soon as you complete them since Monday office hours tend to become crowded. If you worked with a partner, both of you must be present when getting checked off to receive credit. You will only receive credit for the milestones you have checked off by a TA. There is nothing to submit to Moodle for this lab.

Attendance

Per the syllabus, students with more than 3 unexcused lab absences over the course of the semester will automatically fail the course. The TAs will take attendance during lab; it is expected that students will be actively working on the lab material. Your physical presence in lab is not sufficient to be marked as present for the purposes of attendance.

Introduction

As a college student, you probably have a lot of books. For this lab, we’ve decided we’d like to use our computers to represent and search through our numerous books. To facilitate this, you have been provided with a Book class. It contains 3 private variables: a title, an author, and a rating. It also contains getters, setters, a toString method, and a compareTo method (we’ll get into that later).

1. CREATING A BOOKSHELF CLASS

1           Creating a Bookshelf Class

We will store our books in a Bookshelf class. Your Bookshelf will consist of an array of Book objects. It should also contain two constructors – one should take in no arguments, and should initialize the Book array with a default size of 20. The other should take in a single int argument which pertains to the size of the array. Optionally, you can also add a constructor which takes in a Book array to use as the member Book array. Your class should also contain the following methods:

• public boolean add(Book newBook) – Attempt to add a Book to the first empty slot in the Bookshelf. If it is successful, it should return true, and false if not. Do not allow books to be added if the Bookshelf is full.
• public Bookshelf getBooksByAuthor(String author) – return a new Bookshelf object containing only the books which were written by a given author. If no books were written by the given author, the returned Bookshelf should be empty.
• public String toString() – Build a string of all of the Book objects in the array. Separate the each Book with a single newline character.

2           Sorting Our Bookshelf Class

Our bookshelf might be functional, but it may as well not even be called a shelf. There’s no order to it! This could be a pile of books and no one could tell the difference. Therefore, we need to sort it. Handily enough, our Book class comes with a special compareTo method. I’m sure you’ve probably used operators like < or > all the time. These operators, unfortunately, can’t be used on objects. This is where methods such as compareTo come into play. compareTo is very similar to the equals method, except it returns an int based on how the two objects compare. If object a is less than object b, then a.compareTo(b) should return a negative number. If not, it should return a positive number, or zero.

The two compareTo methods already exist in the Book class. It is recommended you take a look at them to see how they are used. For this section of the lab, implement a sort(char sortBy) method in your Bookshelf class which reorders the objects in the Bookshelf so that they correspond to the ascending order of the compareTo method. Feel free to use any reasonable sorting algorithm you have learned to accomplish this task.

3. FILE I/O

3           File I/O

Now we have a working Bookshelf class, and that’s fantastic. However, hardcoding every book’s title, author, and rating and then recompiling every time we want to make a change is incredibly time consuming. This is where file I/O comes in handy. Instead of hardcoding every book’s information into our, we can simply create a method that reads in that information from a file.

(This will also be used in the project, so pay attention).

Your task for this section is to write two methods in a BookshelfReader class. The class does not need a constructor, or any other methods:

• public static Bookshelf readBooksFromFile(String fileName)
• public static void writeShelfToFile(Bookshelf b, String fileName)

The first method will take in a file name (such as the provided bookinput.txt) and create a new Bookshelf object containing all the books in the file. To do so, you will need to import File and Scanner. An example setup for file input is listed below. Once you have a Scanner for the file, you can use it just as you would any other Scanner. The files will be setup just like your toString method, and you may assume both the amount of books in any file is never greater than 20 and commas are never used as a part of a title or author name.

The second method will take in a Bookshelf object and a file name (such as output.txt), and print out all of the books inside the Bookshelf to the file. You will need to import PrintWriter for this task. A PrintWriter object can be called with print or println methods, much like you would call them on System.out.

Example of using PrintWriter and Scanner on a File:

// assume our filename is stored in the string fileName Scanner s = null; // declare s outside try-catch block try { s = new Scanner(new File(fileName));

} catch (Exception e) { // returns false if fails to find fileName return false;

}

// Now use s in the same way we used Scanners previously for user input

4. HONORS

// To write to an arbitrary textfile, do the following:

// assume our filename is stored in the string fileName PrintWriter p = null; // declare p outside try-catch block try { p = new PrintWriter(new File(fileName));

} catch (Exception e) { return false; }

4           Honors

Note: This section and milestone are only required for students in the honors section. Students in other sections do not need to do this, but are still encouraged to work on it if interested and time permits.

Now that we have a way to add books to our shelves, we should provide a way to pull one off it.

Implement the following method in Bookshelf:

public Book remove(String author, String title)

This function should search the array, looking for the book with a certain author and title. If the book isn’t found, return null. If it is, remove it from the books array and return the Book object. Additionally, the remove method should shift all books to fill the gap left by the empty book. Do what is necessary so that add still runs in O(1) time. Be sure to rerun all of your previous unit tests to make sure you didn’t break any functionality.