Songs #

This lab is loosely based on the music platform Spotify.

This lab reviews these skills :

• creating and using classes, objects, methods, attributes, parameters
• arrays of objects
• sequential Search
• bubble Sort
• selection Sort
• BufferedReader .ready .readLine
• String methods .equals(String) .toUpperCase() .toLowerCase()

These concepts are introduced in this lab. By the end of this lab you should be able to identify examples of each concept, and correctly use these terms, and use them in your code

• Do…While loop
• Binary Search

[0] Setup #

Clone the Repository #

💻 select [+ New Project] > [Repository URL] #

Be sure to change yourgithubusername to your actual GitHub username.

https://github.com/isf-dp-cs/lab_songs_yourgithubusername

[1] Song #

The class Post has already been written for you. This UML describes its structure:

classDiagram class Song { -title: String -artist: String -album: String -popularity: int -isExplicit: boolean -genre: String -length: double -energy: double -loudness: double -valence: double + Song(String title, String artist, String album, int popularity, boolean isExplicit, String genre, double length, double energy, double loudness, double valence) + accessor and mutator methods () + toString(): String }

[a] Test Song #

Test out the Song class, to make sure it behaves as you expect

💻 Add a main file to the Song class. It should:

• Create a new Song object
• Print out the Song object
• Use one of the mutators, and then check if it worked by using the corresponding accessor

[2] Melodify | Class Setup #

Here is the UML for the Melodify class:

classDiagram class Melodify { -allSongs: Song[] + Melodify() + getAllSongs(): Song[] + setAllSongs(Song[]): void + sortPopularity(): void + sortValence(): void + getSongByTitle(String title): Song + getSongByPopularity(double target): Song + getSongByValence(double target): Song + getRandomSong(): Song + getRandomPopularSong(int popularity): Song }

[a] Attributes + Constructor #

💻 Create the correct attribute and constructor for the Melodify class, using the UML diagram as a guide.

You can assume that there will be 200 songs in allSongs

[b] Read in All Songs #

In your repository, there is already a file located at "src/allSongs.txt"

💻 In the Melodify class, write a method readPostsFromFile() that reads all Song objects from the text file allSongs.txt into this.allSongs. Hint: reference lab_posts for an example of how to do this

Here is a reference of how to parse the different types of data in allSongs.txt:

String title = data[x]; // read in a String from location x
int popularity = Integer.parseInt(data[x]); // read in an Int from location x
boolean isExplicit = Boolean.parseBoolean(data[x]); // read in an boolean from location x
double length = Double.parseDouble(data[6]); // read in an double from location x

[3] Melodify | Data #

[a] Sort by Popularity 🫧 #

Note: Use Bubble Sort for this method

💻 Write a new method sortPopularity() that sorts allSongs by popularity score in descending order (most popular first). This method has access to allSongs so it does not need any parameters or to return anything.

[b] Sort by Valence ⤵️ #

Note: Use Selection Sort for this method

Valence is a measure of how “happy” a song sounds.

💻 Write a new method sortValence() that sorts allSongs by the valence of the songs in ascending order (lowest values first).

[c] Search By Title 🔎 #

Note: Use Linear Search for this method

💻 Write a new method getSongByTitle(String target) that finds a song with the given title, and returns that song. If it cannot find a song that matches, it should return null.

💻 In the main method of Melodify, test this method to be sure it works.

[d] Search by Popularity 🔎 #

Note: Use Binary Search for this method

💻 Write a new method getSongByPopularity(double target) that finds a song with the given popularity, and returns that song. If it cannot find a song that matches, it should return null. Remember that binary search only works on sorted arrays, so be sure to call one of your sorting methods first.

💻 In the main method of Melodify, test this method to be sure it works.

[e] Search by Valence ⤵️ #

Note: Use Binary Search for this method

This time, you’ll practice using a do...while loop. It’s very similar to a while loop, but you state the action first, before stating this condition, which ensures it will always run at least one time. Here’s an example:

int i = 0;
do {
  System.out.println(i);
  i++;
}
while (i < 5);

💻 Write a new method getSongByValence(double target) that finds a song with the given valence, and returns that song. Use the do...while loop. If it cannot find a song that matches, it should return null. Remember that binary search only works on sorted arrays, so be sure to call one of your sorting methods first.

💻 In the main method of Melodify, test this method to be sure it works.

[f] Get Random Song #

💻 Write a new method getRandomSong() that returns a random Song.

Here’s how to randomly generate a number 0-9:

Random rand = new Random(); // you only need to run this once
int randomIndex = rand.nextInt(10); //each time you need a new random number, run this line of code

[g] Get Random Song by Valence #

💻 Write a new method getRandomPopularSong(int minPopularity) that returns a random Song that is at least as popular as the parameter.

Use do...while in this method.

[4] Deliverables #

⚡✨

Push to Github #

💻 Select Commit from the menu on the left.

Select all your updated files. Be sure to include a descriptive commit message.

💻 Click Commit and Push

💻 Click Push

[5] Extension #

[a] Recursion #

Binary Search is a method that is commonly made recursive. In addition to the target value, it also takes the array, and the left and right indices as parameters.

💻 Create a new method getSongByEnergy(Song[] arr, int left, int right, double target) that uses recursive binary search to find the target song.

[b] Melodify Wrapped #

Now it’s time to create a Melodify Wrapped!

💻 Read in listening data. You can use teacher data, or data from Lawrence, Brendan, or Kenneth if they’re feeling generous.

💻 Try generating a “Melodify Wrapped” for them
Some ideas:

• Calculate their average energy and valence levels, and their most popular genre to give them their label, e.g. “Pink Pilates Princess”, “Indie Sleaze”, etc.
• Calculate their total minutes listened
• Calculate their 5 top artists
• Calculate their 5 top tracks\
• Create their top 100 tracks playlist