debugging/Book.java


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import java.util.*;

public class Book implements Media {

    private String title;
    private String author;
    private List<String> authors;
    private List<Integer> ratings;

    public Book(String title, String author) {
        this.title = title;
        this.author = author;
    }
    
    public Book(String title, List<String> authors) {
        this.title = title;
        this.authors = authors;
    }

    public String getTitle() {
        return this.title;
    }

    public List<String> getArtists() {
        List<String> artists = new ArrayList<>();
        if (this.author != null) {
            artists.add(this.author);
        }
        
        if (this.authors != null) {
            for (String author : authors) {
                artists.add(author);
            }
        }
        return artists;
    }

    public void addRating(int score) {
        if (this.ratings == null) {
            ratings = new ArrayList<>();
        }
        this.ratings.add(score);
    }

    public int getNumRatings() {

        if (this.ratings == null) {
            return 0;
        }
        
        return this.ratings.size();
    }

    public double getAverageRating() {
        if (this.ratings == null) {
            return 0;
        }
        
        int sum = 0;
        for (int rating : ratings) {
            sum += rating;
        }

        return (double)sum / this.ratings.size();
    }

    public String toString() {
        return this.title + " by " + this.getArtists() + ": " + this.getAverageRating() + 
        (this.ratings.size()) + " ratings";
    }
}