ASSIGNMENT 5 SOLUTION

Please read the entire PDF before starting. You must do this assignment individually.




Question 1: 100 points




100 points total




It is very important that you follow the directions as closely as possible. The directions, while perhaps tedious, are designed to make it as easy as possible for the TAs to mark the assignments by letting them run your assignment, in some cases through automated tests. While these tests will never be used to determine your entire grade, they speed up the process signi cantly, which allows the TAs to provide better feedback and not waste time on administrative details. Plus, if the TA is in a good mood while he or she is grading, then that increases the chance of them giving out partial marks. :)




Up to 30% can be removed for bad indentation of your code as well as omitting comments, or poor coding structure. Marks will be removed as well if the class and method names are not respected.




To get full marks, you must:




Follow all directions below




Make sure that your code compiles




{ Non-compiling code will receive a very low mark




Write your name and student ID as a comment in all .java les you hand in Indent your code properly




Name your variables appropriately




{ The purpose of each variable should be obvious from the name




Comment your work




{ A comment every line is not needed, but there should be enough comments to fully understand your program



Part 1 (0 points): Warm-up




Do NOT submit this part, as it will not be graded. However, doing these exercises might help you to do the second part of the assignment, which will be graded. If you have di culties with the questions of Part 1, then we suggest that you consult the TAs during their o ce hours; they can help you and work with you through the warm-up questions. You are responsible for knowing all of the material in these questions.




Warm-up Question 1 (0 points)




Write a program that opens a .txt, reads the contents of the le line by line, and prints the content of each line. To do this, you should look up how to use the BufferedReader or FileReader class1. Remember to use the try and catch blocks to handle errors like trying to open an non-existent le. A sample le for testing le reading is found in the provided les as dictionary.txt.




Warm-up Question 2 (0 points)




Modify the previous program so that it stores every line in an ArrayList of String objects. You have to properly declare an ArrayList to store the results, and use add to store every line that your program reads in the ArrayList.




Warm-up Question 3 (0 points)




Modify your program so that, after reading all the content in the le, it prints how many words are inside the text le. To do this, you should use the split method of the String class. Assume the only character that separates words is whitespace " ".




Warm-up Question 4 (0 points)




Create a new method in your program which takes your ArrayList of Strings, and writes it to a le. Use the FileWriter and BufferedWriter classes in order to access the le and write the Strings. In the output le, there should be one String per line, just like the original le you loaded the ArrayList from.




Warm-up Question 5 (0 points)




Create a new method in your program which takes as input your ArrayList of Strings, and sort all the elements. The sorting criterion will be the length of the string. In other words, after calling this method, the shortest string must be located in the rst position, the second shortest in the second position an so on.




Warm-up Question 6 (0 points)




Create a new method in your program which takes as input a sorted ArrayList (see the previous question for details about the sorting criterion) and two ints. The two ints will represent a range of values. This method should return an ArrayList with all the Strings whose length is inside that range. For example, if your original ArrayList is equal to f"aa","aaa","aaaa","aaaaa"g and the two ints are 3 and 4, your method must return the ArrayList f"aaa","aaaa"g (because the length of the returned Strings is within 3 and 4).







Part 2




The questions in this part of the assignment will be graded.




Question 1: Twitter (100 points)




For this question, you will write two classes to create a new data type that will model information extracted from twitter. Your code for this question will go in two .java les.




We strongly recommend that you complete all the warm-up questions before starting this problem.




Note that in addition to the required methods below, you are free to add as many other private methods as you want.




Tweet Class



Tweet.java stores information and behaviours about a tweet. A tweet is a message sent using the social network Twitter. For this assignment, the tweets are de ned as messages from 1 to 15 words (after omitting stop words). The Tweet class stores information about a tweet: the user who tweeted it, the date of the tweet, the time of the tweet, and the actual tweet message.




The Tweet class should contain the following private attributes:




A String userAccount;




This attribute stores the user id.




A String date;




This attribute stores the date on which the tweet was tweeted.




A String time;




This attribute stores the time on which the tweet was tweeted.




A String message;




This attribute stores the tweeted message




The Tweet class should also contain a private static attribute:




An HashSet<String stopWords.




This attribute stores the set of stop-words. A stop word is a commonly used word that is ignored by search engines2




Regarding the behaviour of the class, Tweet must implement the following methods:




A constructor that takes as inputs four Strings. The Strings correspond to: i) the user account ii) the date on which the tweet was posted. The format of the date is YYYY-MM-DD. iii) the time on which the tweet was posted. The format of time is HH:MM:SS and iv) the message of the tweet. Please notice that your arguments must respect the previous order. The constructor does not have to check the format of the inputs.




A public non-static checkMessage method which takes no input. This method will check if the message of this Tweet is valid or not. The method returns true if if the message contains less than 16 words and more than 0 (excluding the stop-words). If the HashSet stopWords is equal to null, checkMessage must throw a NullPointerException indicating that the HashSet has not been initialized.




Here a couple of hints.




{ You can use the split method of the String class to separate the words of the message. For this assignment, you can assume that the whitespace will be the only character that separates words [See warm-up question 3]).







h
{ You can use the equalsIgnoreCase method to make sure not to miss stopWords typed in either upper or lower case).




{ You will also have to control cases where the stopWord might have a punctuation character appended to it [e.g., both \any" or \any," should be considered]. For this assignment, you can assume that the only punctuation characters appended to stop-words are ‘,’, ‘.’, ‘;’ or ‘:’.




{ You can create a public static method isStopWord that takes a String as input and returns true if it’s a stop word, false otherwise. NOTE: if you do not create this method, then make the attribute stopWords public. This is the only additional public method you can write, all other helper methods should be private.




getDate




This returns the date instance variable.




getTime




This returns the time instance variable.




getMessage




This returns the message instance variable.




getUserAccount




This returns the userAccount instance variable.




toString




This method returns a new String that is the concatenation of the userAccount, a tab char-acter, the date, a tab character, the time, a tab character, and the tweeted message in the end.




isBefore




This method takes as a parameter an instance of Tweet and it returns true when this tweet was posted at an earlier time than the input parameter. Otherwise the method returns false. Remember that the formats of the date and time attributes are YYYY-MM-DD and HH:MM:SS, respectively.




loadStopWords




This static procedure loadStopWords gets as input the name of a le that contains a set of stop words. The le has only one column containing a stop word in each line. This method should read the le and initialize the static attribute stopWords. This method has no return value.




Twitter Class


Twitter.java stores information and behaviours generated by the twitter social network 3. The Twitter class should contain the following private variable:




ArrayList<Tweet tweets




This attribute stores a collection of valid tweets.




Regarding the behaviour of the class, Twitter must implement the following public methods:




Twitter




This constructor takes no arguments and it initializes tweets as an empty ArrayList.




loadDB




loadDB takes as argument the name of a le (i.e., its relative path) that contains a collection of tweets. Particularly, we provide to you the le called tweets.txt, which has four columns that are separated by tabs. The rst column contains the userAccount, the second and third contain the date and time on which the post was made, respectively. Finally, the fourth column




corresponds to the posted message itself. loadDB must read the le line-by-line (please see the warm up questions), construct the corresponding Tweet object, if valid, the Tweet should be added to the ArrayList of Tweets (Hint: remember that you already coded a method to check if a tweet is valid or not). If the tweet is found to be not valid, your program should simply not put it into the ArrayList of Tweets. Once, all the valid tweets are stored in the ArrayList tweets loadDB must call the function sortTwitter to sort the list.




sortTwitter




sortTwitter takes no arguments and it sorts (in increasing order) the Tweet instances based on their date/time of publication. Here, you are free to select the sorting algorithm. This method has no return value.




getSizeTwitter




This returns the number of tweets in the data base.




getTweet




This method receives an index and returns the tweet stored at that index.




printDB It returns a String that contains all the elements currently stored in the ArrayList tweets. The format of the output must be the same as the one used in the tweets.txt le (i.e., the rst column contains the userAccount, the second and third contains the date and time the post was made, respectively. Finally, the fourth is the posted message). (Hint: use the toString method from the Tweet class)




rangeTweets




rangeTweets gets as parameters two instances of Tweet (i.e., tweet1 and tweet2) and it returns a new ArrayList of Tweets containing those tweet posted between the date/time of tweet1 and tweet2 (inclusive). You can assume that tweet1 and tweet2 are elements of the ArrayList tweets. Please notice that there is not guarantee that tweet1 was posted before tweet2. The method should verify which of those two tweets is the earliest. You can assume that the ArrayList tweets is sorted given that sortTwitter() was already called by loadDB.




saveDB




saveDB gets one parameters, the name of a le. saveDB must write in the le the list of Tweet following the same format of the tweets.txt le. (Hint: Use the printDB method to obtain the String to write).




trendingTopic




trendingTopic receives no parameters and it returns the word (that is not a stop word) that is the most frequent in the tweets from the data base. The most common word is chosen from the data base by counting in how many tweet messages the word appears (i.e., if a word appears more than once in a tweet message, it is counted only once).




Main Method



Your main method will not be graded. However, we strongly advise that you write a main method in your class Twitter to test your code. You may include it in your submission as long as it compiles. In the following lines, we will report di erent versions of our main method. Like that, you will have some test cases to test your code.




Example 1.




public static void main(String[] args){ Twitter example = new Twitter(); example.loadDB("tweets.txt");




}




The result of running Example 1 is:




Error checking the stopWords database: The file of stopWords has not been loaded yet



Comments: In this example, the function loadDB caught a NullPointerException thrown by checkMessage




Example 2.




public static void main(String[] args){ Twitter example = new Twitter(); Tweet.loadStopWords("stopWords.txt"); example.loadDB("tweets.txt");




System.out.println("The number of tweets is: " +example.getSizeTwitter());




}




The result of running Example 2 is: The number of tweets is: 58




Comments: The le tweets.txt contains initially 61 tweets. However, 3 tweets where dis-carded because their length was not greater than zero or less than sixteen. Particularly, the message \I can be MADE into a need." has length zero after subtracting the stop words (i.e., all the words in the message are stop words). On the other hand, the messages \USER 55cc3d0f i’m kidding. i’ll die! lol jk i guess i’d be alright but not for a couple days or hours cause i’m always a happy spirit lol" and \RT USER 3a117437: The woman at the rental car spot tried 2 give us a Toyota! No ma’am lk the old spiritual says \aint got time 2 die!"" were dis-carded because they have 18 and 16 words (after subtracting the stop words [which are shown in bold]), respectively.




Example 3.




public static void main(String[] args){ Twitter example = new Twitter(); Tweet.loadStopWords("stopWords.txt"); example.loadDB("tweets.txt"); System.out.println(example.printDB());




}




The result of running Example 3 is:




USER_a75657c2 2010-03-03 00:02:54 @USER_13e8a102 They reached a compromise




.............




.




.




.




.............




USER_a75657c2 2010-03-07 21:45:48 So SunChips made a bag that is 100% biodegradeable. It is about damn time somebody did.




Comments: Here you should see the 58 elements sorted by date/time. We are just showing the rst tweet (posted on 2010-03-03 00:02:54) and the last tweet (posted on 2010-03-07)




Example 4.



public static void main(String[] args){ Twitter example = new Twitter(); Tweet.loadStopWords("stopWords.txt"); example.loadDB("tweets.txt"); System.out.println(example.rangeTweets(example.getTweet(4), example.getTweet(2)));







}




The result of running Example 4 is:




[USER_1e22f6a5 2010-03-03 00:20:45 RT @USER_561fe280: Nourish your .....,




USER_36607a99 2010-03-03 02:06:01 RT @USER_561fe280: Nourish your .....,




USER_c271e4ac 2010-03-03 02:07:37 I want a King Kong roll from Sushi .....]




Comments: Here you should obtain a sorted list of three tweets.




Example 5.




public static void main(String[] args){ Twitter example = new Twitter(); Tweet.loadStopWords("stopWords.txt"); example.loadDB("tweets.txt"); System.out.println(example.trendingTopic());




}




The result of running Example 5 is: spirit




Comments: The word \spirit" is the most common word and it appears in 26 tweets.







What To Submit




You have to submit one zip le that contains all your les to myCourses - Assignment 5. If you do not know how to zip les, please obtain that information from any search engine or friends. Google might be your best friend with this, and for a lot of di erent little problems as well.




These les should all be inside your zip. Do not submit any other les, especially .class les.




Twitter.java




Tweet.java




Confession.txt (optional) In this le, you can tell the TA about any issues you ran into doing this assignment. If you point out an error that you know occurs in your problem, it may lead the TA to give you more partial credit. On the other hand, it also may lead the TA to notice something that otherwise they would not.