Question

1. Write a Java program that implements a song database. The SongsDatabase class keeps tracks of song titles by classifying them according to genre (e.g., Pop, Rock, etc.). The class uses a HashMap to map a genre with a set of songs that belong to such a genre. The set of songs will be represented using a HashSet. Your driver output should sufficiently prove that your code properly implements the code below.

public class SongsDatabase {

private Map<String, Set<String>> genreMap =

new HashMap<String, Set<String>>();

    public void addSong(String genre, String songTitle) {

        // You must implement this method

    }

    public Set<String> getSongs(String genre) {

        // You must implement this method

    }

    public String getGenreOfSong(String songTitle) {

        // You must implement this method

    }

}

So, your hashMap, visually, looks like the following:

Soul -> (SoulSong1, SoulSong2, SoulSong3, etc.)

Rock -> (RockSong1, RockSong2, RockSong3, etc.)

Jazz -> (JazzSong1, JazzSong2, JazzSong3, etc.)

Answer 1

Code:

import java.util.*;

public class SongsDatabase {

    private Map<String, Set<String>> genreMap = new HashMap<String, Set<String>>();
    
        public void addSong(String genre, String songTitle) {
    
            // You must implement this method
            if(genreMap.containsKey(genre)){
                genreMap.get(genre).add(songTitle);//adding songTitle with genre
            }else{
                //making a new set when the genre does not exist and adding it to the hashmap
                Set<String> newSet = new HashSet<String>();
                newSet.add(songTitle);
                genreMap.put(genre,newSet);
            }
    
        }
    
        public Set<String> getSongs(String genre) {
    
            // You must implement this method
            return genreMap.get(genre);//returning the set corresponding to the genre
    
        }
    
        public String getGenreOfSong(String songTitle) {
    
            // You must implement this method
            for (Map.Entry<String, Set<String>> entry : genreMap.entrySet()) {
                
                if(entry.getValue().contains(songTitle)){
                    return entry.getKey();
                }
            
            }

            return "No value found";
    
        }

        public static void main(String args[]){
            SongsDatabase db = new SongsDatabase();

            //adding songs
            db.addSong("Soul","SoulSong1");
            db.addSong("Soul","SoulSong2");
            db.addSong("Soul","SoulSong3");
            db.addSong("Rock","RockSong1");
            db.addSong("Rock","RockSong2");
            db.addSong("Rock","RockSong3");
            db.addSong("Jazz","JazzSong1");
            db.addSong("Jazz","JazzSong2");

            //getting songs 
            Set<String> set = db.getSongs("Rock");
            Iterator value = set.iterator();
            System.out.println("Songs in Rock genre:");
            while(value.hasNext()){
                System.out.println(value.next());
            }

            System.out.print("Getting genre of the song SoulSong3 : ");
            System.out.println(db.getGenreOfSong("SoulSong3"));
        }
    
}

Output:

Code screenshot: