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Stanislav Rakitov
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Merge pull request #1 from ProsperousRF/Week2
Week2 Complete
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‎.idea/modules.xml

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‎Week1/src/FirstRatings.java

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* @version 1.0
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*/
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public class FirstRatings {
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public ArrayList<Movie> getMovieArrayList() {
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return movieArrayList;
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}
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public ArrayList<Rater> getRaterArrayList() {
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return raterArrayList;
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}
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private ArrayList<Movie> movieArrayList;
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/**
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* This method returns number of unique Raters
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*
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* @return int number of unique raters
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*/
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public int getRatersNumber() {
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return ratersWithIds.size();
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}
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private ArrayList<Rater> raterArrayList;
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private HashMap<String, HashSet<String>> directorsAndItsMovies;

‎Week2/Week2.iml

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<?xml version="1.0" encoding="UTF-8"?>
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<module type="JAVA_MODULE" version="4">
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<component name="NewModuleRootManager" inherit-compiler-output="true">
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<exclude-output />
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<content url="file://$MODULE_DIR$">
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<sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
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</content>
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<orderEntry type="inheritedJdk" />
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<orderEntry type="sourceFolder" forTests="false" />
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<orderEntry type="module" module-name="Week1" />
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</component>
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</module>

‎Week2/src/MovieRunnerAverage.java

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import java.util.ArrayList;
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import java.util.Collections;
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public class MovieRunnerAverage {
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private final SecondRatings secondRatings;
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public MovieRunnerAverage() {
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secondRatings = new SecondRatings("ratedmoviesfull.csv", "ratings.csv");
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}
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public void printAverageRatings(int minimalRatings) {
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// SecondRatings secondRatings = new SecondRatings("ratedmovies_short.csv",
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// "ratings_short.csv");
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// System.out.printf(
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// "Total number of movies %d, total number of raters %d\n",
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// secondRatings.getMovieSize(), secondRatings.getRaterSize());
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/*
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* In the MovieRunnerAverage class in the printAverageRatings method,
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* add code to print a list of movies and their average ratings,
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* for all those movies that have at least a specified number of ratings,
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* sorted by averages.
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* Specifically, this method should print the list of movies,
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* one movie per line (print its rating first, followed by its title)
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* in sorted order by ratings, lowest rating to highest rating.
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* For example, if printAverageRatings is called on the files
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* ratings_short.csv and ratedmovies_short.csv with the argument 3,
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* then the output will display two movies:
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*
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* 8.25 Her
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* 9.0 The Godfather
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* */
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ArrayList<Rating> ratedList = secondRatings.getAverageRatings(minimalRatings);
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Collections.sort(ratedList);
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System.out.printf("Total movies with %d ratings is %d\n", minimalRatings, ratedList.size());
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System.out.printf(
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"The name of the movie that has the lowest rating is \"%s\"\n",
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secondRatings.getTitle(ratedList.get(0).getItem()));
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// for (Rating ratedObj : ratedList) {
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// double rating = ratedObj.getValue();
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// String movieID = ratedObj.getItem();
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// String movieTitle = secondRatings.getTitle(movieID);
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// System.out.println(rating + " " + movieTitle);
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// }
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}
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Double getAverageRatingOneMovie(String movieTitle) {
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String movieID = secondRatings.getID(movieTitle);
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return secondRatings.getAverageByID(movieID, 1);
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}
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}

‎Week2/src/SecondRatings.java

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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.Map;
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import java.util.Objects;
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/**
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* Week2. A new class to do many of the calculations focusing on computing averages on movie
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* ratings.
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*
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* @author Stanislav Rakitov
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* @version 1.0
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*/
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public class SecondRatings {
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private final ArrayList<Movie> myMovies;
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private final ArrayList<Rater> myRaters;
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private final FirstRatings firstRatings;
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private final HashMap<String, ArrayList<Double>> moviesAndRatings;
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private final HashMap<String, String> moviesIdAndTitles;
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public SecondRatings() {
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// default constructor
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this("ratedmoviesfull.csv", "ratings.csv");
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}
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// The constructor should create a FirstRatings object and then call the loadMovies and
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// loadRaters methods in FirstRatings to read in all the movie and ratings data and store them
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// in the two private ArrayList variables of the SecondRatings class, myMovies and myRaters.
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public SecondRatings(String moviesFileName, String ratingsFileName) {
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firstRatings = new FirstRatings(moviesFileName, ratingsFileName);
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myMovies = firstRatings.getMovieArrayList();
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myRaters = firstRatings.getRaterArrayList();
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moviesAndRatings = getMoviesAndRatingsMap();
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moviesIdAndTitles = getAllMoviesAndTitlesMap();
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}
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// Get all movies and titles map
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private HashMap<String, String> getAllMoviesAndTitlesMap() {
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HashMap<String, String> map = new HashMap<>();
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for (Movie movie : myMovies) {
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String movieID = movie.getID();
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String movieTitle = movie.getTitle();
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map.put(movieID, movieTitle);
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}
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return map;
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}
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// Returns a Map with movieID and all its ratings
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private HashMap<String, ArrayList<Double>> getMoviesAndRatingsMap() {
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HashMap<String, ArrayList<Double>> map = new HashMap<>();
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for (Movie movie : myMovies) {
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map.putIfAbsent(movie.getID(), new ArrayList<>());
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}
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for (Rater rater : myRaters) {
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ArrayList<String> ratings = rater.getItemsRated();
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for (String movieID : ratings) {
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// String movieID, double rating
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ArrayList<Double> list = map.get(movieID);
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list.add(rater.getRating(movieID));
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}
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}
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return map;
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}
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/**
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* A public method which returns the number of movies that were read in and stored in the
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* ArrayList of type Movie
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*
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* @return int number of movies
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*/
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public int getMovieSize() {
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return this.myMovies.size();
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}
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/**
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* A public method which returns the number of raters that were read in and stored in the
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* ArrayList of type Rater.
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*
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* @return int number of movies
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*/
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public int getRaterSize() {
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return this.firstRatings.getRatersNumber();
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}
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/*
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This method returns a double representing the average movie rating for this ID
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if there are at least minimalRaters ratings.
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If there are not minimalRaters ratings, then it returns 0.0.
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*/
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Double getAverageByID(String id, Integer minimalRaters) {
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double result = 0.0;
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ArrayList<Double> ratings = moviesAndRatings.get(id);
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if (ratings != null && ratings.size() >= minimalRaters) {
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result = ratings.stream().mapToDouble(d -> d).average().orElse(0.0);
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}
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// If there are no ratings returns 0.0
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return result;
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}
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/**
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* This method should find the average rating for every movie that has been rated by at least
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* minimalRaters raters.
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*
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* @param minimalRaters int the minimal number of raters supplying a rating
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* @return an ArrayList of all the Rating objects for movies that have at least the minimal number
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* of raters supplying a rating
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*/
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public ArrayList<Rating> getAverageRatings(int minimalRaters) {
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ArrayList<Rating> list = new ArrayList<>();
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for (Movie movie : myMovies) {
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String movieID = movie.getID();
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Double averageRating = getAverageByID(movieID, minimalRaters);
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if (averageRating != 0.0) {
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list.add(new Rating(movieID, averageRating));
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}
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}
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return list;
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}
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/*
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* This method returns the title of the movie with that ID.
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* If the movie ID does not exist, then this method should return a String
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* indicating the ID was not found.
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* */
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String getTitle(String id) {
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String title = moviesIdAndTitles.get(id);
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if (title != null) {
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return title;
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}
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// No title found
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return "ID " + id + " NOT FOUND";
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}
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/*
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* This method returns the movie ID of this movie.
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* If the title is not found, return “NO SUCH TITLE.
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* */
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String getID(String title) {
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String result = "NO SUCH TITLE";
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for (Map.Entry<String, String> entry : moviesIdAndTitles.entrySet()) {
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if (Objects.equals(title, entry.getValue())) {
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return entry.getKey();
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}
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}
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return result;
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}
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}

‎Week2/src/Week2.java

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public class Week2 {
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public static void main(String[] args) {
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MovieRunnerAverage average = new MovieRunnerAverage();
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System.out.printf(
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"Q5. What is the rating of the movie “The Maze Runner”? - %.4f\n",
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average.getAverageRatingOneMovie("The Maze Runner"));
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System.out.printf(
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"Q6. What is the rating of the movie “Moneyball”? - %.4f\n",
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average.getAverageRatingOneMovie("Moneyball"));
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System.out.printf(
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"Q7. what is the rating of the movie “Vacation”? - %.4f\n",
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average.getAverageRatingOneMovie("Vacation"));
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// Q8. Using the files ratedmoviesfull.csv and ratings.csv, how many movies have 50 or more
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// ratings?
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average.printAverageRatings(50);
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// Q9. Using the files ratedmoviesfull.csv and ratings.csv, of those movies that have at least
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// 20 ratings,
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// what is the name of the movie that has the lowest rating?
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average.printAverageRatings(20);
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// Using the files ratedmoviesfull.csv and ratings.csv,
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// of those movies that have at least 12 ratings,
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// what is the name of the movie that has the lowest rating?
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average.printAverageRatings(12);
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}
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}

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