Week2

Week1/src/FirstRatings.java

@@ -15,7 +15,25 @@
  * @version 1.0
  */
 public class FirstRatings {
+  public ArrayList<Movie> getMovieArrayList() {
+    return movieArrayList;
+  }
+
+  public ArrayList<Rater> getRaterArrayList() {
+    return raterArrayList;
+  }
+
   private ArrayList<Movie> movieArrayList;
+
+  /**
+   * This method returns number of unique Raters
+   *
+   * @return int number of unique raters
+   */
+  public int getRatersNumber() {
+    return ratersWithIds.size();
+  }
+
   private ArrayList<Rater> raterArrayList;
 
   private HashMap<String, HashSet<String>> directorsAndItsMovies;

Week2/Week2.iml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+    <orderEntry type="module" module-name="Week1" />
+  </component>
+</module>

Week2/src/MovieRunnerAverage.java

@@ -0,0 +1,51 @@
+import java.util.ArrayList;
+import java.util.Collections;
+
+public class MovieRunnerAverage {
+  private final SecondRatings secondRatings;
+
+  public MovieRunnerAverage() {
+    secondRatings = new SecondRatings("ratedmoviesfull.csv", "ratings.csv");
+  }
+
+  public void printAverageRatings(int minimalRatings) {
+    //    SecondRatings secondRatings = new SecondRatings("ratedmovies_short.csv",
+    // "ratings_short.csv");
+    //    System.out.printf(
+    //        "Total number of movies %d, total number of raters %d\n",
+    //        secondRatings.getMovieSize(), secondRatings.getRaterSize());
+
+    /*
+     * In the MovieRunnerAverage class in the printAverageRatings method,
+     * add code to print a list of movies and their average ratings,
+     * for all those movies that have at least a specified number of ratings,
+     * sorted by averages.
+     * Specifically, this method should print the list of movies,
+     * one movie per line (print its rating first, followed by its title)
+     * in sorted order by ratings, lowest rating to highest rating.
+     * For example, if printAverageRatings is called on the files
+     * ratings_short.csv and ratedmovies_short.csv with the argument 3,
+     * then the output will display two movies:
+     *
+     * 8.25 Her
+     * 9.0 The Godfather
+     * */
+    ArrayList<Rating> ratedList = secondRatings.getAverageRatings(minimalRatings);
+    Collections.sort(ratedList);
+    System.out.printf("Total movies with %d ratings is %d\n", minimalRatings, ratedList.size());
+    System.out.printf(
+        "The name of the movie that has the lowest rating is \"%s\"\n",
+        secondRatings.getTitle(ratedList.get(0).getItem()));
+    //    for (Rating ratedObj : ratedList) {
+    //      double rating = ratedObj.getValue();
+    //      String movieID = ratedObj.getItem();
+    //      String movieTitle = secondRatings.getTitle(movieID);
+    //      System.out.println(rating + " " + movieTitle);
+    //    }
+  }
+
+  Double getAverageRatingOneMovie(String movieTitle) {
+    String movieID = secondRatings.getID(movieTitle);
+    return secondRatings.getAverageByID(movieID, 1);
+  }
+}

Week2/src/SecondRatings.java

@@ -0,0 +1,151 @@
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+
+/**
+ * Week2. A new class to do many of the calculations focusing on computing averages on movie
+ * ratings.
+ *
+ * @author Stanislav Rakitov
+ * @version 1.0
+ */
+public class SecondRatings {
+  private final ArrayList<Movie> myMovies;
+  private final ArrayList<Rater> myRaters;
+  private final FirstRatings firstRatings;
+  private final HashMap<String, ArrayList<Double>> moviesAndRatings;
+  private final HashMap<String, String> moviesIdAndTitles;
+
+  public SecondRatings() {
+    // default constructor
+    this("ratedmoviesfull.csv", "ratings.csv");
+  }
+
+  // The constructor should create a FirstRatings object and then call the loadMovies and
+  // loadRaters methods in FirstRatings to read in all the movie and ratings data and store them
+  // in the two private ArrayList variables of the SecondRatings class, myMovies and myRaters.
+  public SecondRatings(String moviesFileName, String ratingsFileName) {
+    firstRatings = new FirstRatings(moviesFileName, ratingsFileName);
+    myMovies = firstRatings.getMovieArrayList();
+    myRaters = firstRatings.getRaterArrayList();
+    moviesAndRatings = getMoviesAndRatingsMap();
+    moviesIdAndTitles = getAllMoviesAndTitlesMap();
+  }
+
+  // Get all movies and titles map
+  private HashMap<String, String> getAllMoviesAndTitlesMap() {
+    HashMap<String, String> map = new HashMap<>();
+    for (Movie movie : myMovies) {
+      String movieID = movie.getID();
+      String movieTitle = movie.getTitle();
+      map.put(movieID, movieTitle);
+    }
+    return map;
+  }
+
+  // Returns a Map with movieID and all its ratings
+  private HashMap<String, ArrayList<Double>> getMoviesAndRatingsMap() {
+    HashMap<String, ArrayList<Double>> map = new HashMap<>();
+
+    for (Movie movie : myMovies) {
+      map.putIfAbsent(movie.getID(), new ArrayList<>());
+    }
+
+    for (Rater rater : myRaters) {
+      ArrayList<String> ratings = rater.getItemsRated();
+      for (String movieID : ratings) {
+        // String movieID, double rating
+        ArrayList<Double> list = map.get(movieID);
+        list.add(rater.getRating(movieID));
+      }
+    }
+
+    return map;
+  }
+
+  /**
+   * A public method which returns the number of movies that were read in and stored in the
+   * ArrayList of type Movie
+   *
+   * @return int number of movies
+   */
+  public int getMovieSize() {
+    return this.myMovies.size();
+  }
+
+  /**
+   * A public method which returns the number of raters that were read in and stored in the
+   * ArrayList of type Rater.
+   *
+   * @return int number of movies
+   */
+  public int getRaterSize() {
+    return this.firstRatings.getRatersNumber();
+  }
+
+  /*
+  This method returns a double representing the average movie rating for this ID
+  if there are at least minimalRaters ratings.
+  If there are not minimalRaters ratings, then it returns 0.0.
+  */
+  Double getAverageByID(String id, Integer minimalRaters) {
+    double result = 0.0;
+    ArrayList<Double> ratings = moviesAndRatings.get(id);
+    if (ratings != null && ratings.size() >= minimalRaters) {
+      result = ratings.stream().mapToDouble(d -> d).average().orElse(0.0);
+    }
+
+    // If there are no ratings returns 0.0
+    return result;
+  }
+
+  /**
+   * This method should find the average rating for every movie that has been rated by at least
+   * minimalRaters raters.
+   *
+   * @param minimalRaters int the minimal number of raters supplying a rating
+   * @return an ArrayList of all the Rating objects for movies that have at least the minimal number
+   *     of raters supplying a rating
+   */
+  public ArrayList<Rating> getAverageRatings(int minimalRaters) {
+    ArrayList<Rating> list = new ArrayList<>();
+    for (Movie movie : myMovies) {
+      String movieID = movie.getID();
+      Double averageRating = getAverageByID(movieID, minimalRaters);
+      if (averageRating != 0.0) {
+        list.add(new Rating(movieID, averageRating));
+      }
+    }
+    return list;
+  }
+
+  /*
+   * This method returns the title of the movie with that ID.
+   * If the movie ID does not exist, then this method should return a String
+   * indicating the ID was not found.
+   * */
+  String getTitle(String id) {
+    String title = moviesIdAndTitles.get(id);
+    if (title != null) {
+      return title;
+    }
+    // No title found
+    return "ID " + id + " NOT FOUND";
+  }
+  /*
+   * This method returns the movie ID of this movie.
+   * If the title is not found, return “NO SUCH TITLE.
+   * */
+  String getID(String title) {
+    String result = "NO SUCH TITLE";
+
+    for (Map.Entry<String, String> entry : moviesIdAndTitles.entrySet()) {
+      if (Objects.equals(title, entry.getValue())) {
+        return entry.getKey();
+      }
+    }
+
+    return result;
+  }
+}

Week2/src/Week2.java

@@ -0,0 +1,32 @@
+public class Week2 {
+  public static void main(String[] args) {
+    MovieRunnerAverage average = new MovieRunnerAverage();
+
+    System.out.printf(
+        "Q5. What is the rating of the movie “The Maze Runner”? - %.4f\n",
+        average.getAverageRatingOneMovie("The Maze Runner"));
+
+    System.out.printf(
+        "Q6. What is the rating of the movie “Moneyball”? - %.4f\n",
+        average.getAverageRatingOneMovie("Moneyball"));
+
+    System.out.printf(
+        "Q7. what is the rating of the movie “Vacation”? - %.4f\n",
+        average.getAverageRatingOneMovie("Vacation"));
+
+    // Q8. Using the files ratedmoviesfull.csv and ratings.csv, how many movies have 50 or more
+    // ratings?
+    average.printAverageRatings(50);
+
+    // Q9. Using the files ratedmoviesfull.csv and ratings.csv, of those movies that have at least
+    // 20 ratings,
+    // what is the name of the movie that has the lowest rating?
+
+    average.printAverageRatings(20);
+
+    // Using the files ratedmoviesfull.csv and ratings.csv,
+    // of those movies that have at least 12 ratings,
+    // what is the name of the movie that has the lowest rating?
+    average.printAverageRatings(12);
+  }
+}