Question

You are given the following class definition (assume all methods are correctly implemented):

public class Song {
...
public Song(String name, String artist) { ... }
public String getName() { ... }
public String getArtist() { ... }
public String getGenre() { ... }
public int copiesSold() { ... }
}

Write NAMED and TYPED lambda expressions for each of the following, using appropriate functional interfaces from the java.util.function and java.util packages (Only the lambda expression with no type+name will get max half credit):

An expression that can be passed as argument to the sort method of a List of songs, for sorting in ascending order of copies sold.

Java Lambda

Answer 1

package javaapplication620;

public class SongDriver {

public static void main(String[] args) {
Playlist one = new Playlist();

Song song1 = new Song("Hotline Bling", "Drake", "Hotline Bing - Single", 267000);
Song song2 = new Song("What Do You Mean?", "Justin Bieber", "What Do You Mean? - Single", 207000);
Song song3 = new Song("Watch Me", "Silento", "Watch Me (Whip / Nae Nae) - Single", 185000);
Song song4 = new Song("679", "Fetty Wap ft. Remy Boyz", "Fetty Wap", 185000);
Song song5 = new Song("Can't Feel My Face", "The Weeknd", "Beauty Behind the Madness", 213000);
Song song6 = new Song("Good for You", "Selena Gomez ft. A$AP Rocky", "Good for You - Single", 221000);
Song song7 = new Song("If You", "Big Bang", "MADE", 264000);

one.add(song1);
one.add(song2);
one.add(song3);
one.add(song4);
one.add(song5);
one.add(song6);
one.add(song7);

one.print();

one.remove("679");
one.remove("Watch Me");

one.print();
one.clear();
}

public static long HOURS = 60 * 60 * 1000;
public static long MINS = 60 * 1000;
public static long SECS = 1000;

public static class Playlist {

private Song[] songs;
private int count;
private String playlistName;

public Playlist() {
songs = new Song[12];
count = 0;
}

public String getPlaylistName() {
return playlistName;
}

public void setPlayListName() {
this.playlistName = playlistName;
}

public void add(Song a) {
if (count == songs.length) {
System.out.println("ERROR: Collection is full. Songs were not added to the Playlist.");
}
songs[count] = a;
count++;
}

public Song get(int i) {
if (count > i) {
return songs[i];
} else {
return null;
}
}

public Song remove(String name) {
boolean found = false;
int indexToRemove = 0;
while (indexToRemove < count && !found) {
if (songs[indexToRemove].getName().equals(name)) {
found = true;
} else {
indexToRemove++;
}
}
if (indexToRemove < count) {
for (int from = indexToRemove + 1; from < count; from++) {
songs[from - 1] = songs[from];
}
songs[count - 1] = null;
count--;
}
return null;
}

public void print() {
String result = "NumSongs = " + count
+ " / PlayList song limit = " + songs.length + "\n";

for (int i = 0; i < count; i++) {
result += ("songList[" + i + "] = <"
+ songs[i] + ">\n");
}
result += " / " + formattedTotalTime();
System.out.println(result.toString());
}

public int size() {
return count;
}

public int totalTime() {
int totalTime = 0;
for (int i = 0; i < count; i++) {
totalTime += songs[i].getLength();
}
return totalTime;
}

public String formattedTotalTime() {
return formatTime(totalTime());
}

public void clear() {
for (int i = 0; i < songs.length; i++) {
songs[i] = null;
count = 0;
}
return;
}
}

public static class Song {

public String name;
public String artist;
public String album;
public int length;

public Song(String songName, String artistName, String albumName, int trackLength) {
this.name = songName;
this.artist = artistName;
this.album = albumName;
this.length = trackLength;
}

public void setName(String songName) {
name = songName;
}

public String getName() {
return name;
}

public void setArtist(String artistName) {
artist = artistName;
}

public String getArtist() {
return artist;
}

public void setAlbum(String albumName) {
album = albumName;
}

public String getAlbum() {
return album;
}

public void setLength(int h, int m, int s) {
length = (h * 3600 + m * 60 + s);
if (h == 0) {
length = (m * 60 + s);
}
}

public int getLength() {
return length;
}

public String toString() {
return "Title: " + getName() + ", Artist: " + getArtist()
+ ", Album: " + getAlbum() + ", Track Length: " + formatTime(getLength());
}

}

public static String formatTime(long time) {
long overflow = time;
long h = time / HOURS;
overflow = time % HOURS;
long m = overflow / MINS;
overflow = time % MINS;
long s = overflow / SECS;
return String.format("%02d:%02d.%02d", h, m, s);

}
}

This test code currently prints out:

NumSongs = 7 / PlayList song limit = 12
songList[0] = <Title: Hotline Bling, Artist: Drake, Album: Hotline Bing - Single, Track Length: 00:04.27>
songList[1] = <Title: What Do You Mean?, Artist: Justin Bieber, Album: What Do You Mean? - Single, Track Length: 00:03.27>
songList[2] = <Title: Watch Me, Artist: Silento, Album: Watch Me (Whip / Nae Nae) - Single, Track Length: 00:03.05>
songList[3] = <Title: 679, Artist: Fetty Wap ft. Remy Boyz, Album: Fetty Wap, Track Length: 00:03.05>
songList[4] = <Title: Can't Feel My Face, Artist: The Weeknd, Album: Beauty Behind the Madness, Track Length: 00:03.33>
songList[5] = <Title: Good for You, Artist: Selena Gomez ft. A$AP Rocky, Album: Good for You - Single, Track Length: 00:03.41>
songList[6] = <Title: If You, Artist: Big Bang, Album: MADE, Track Length: 00:04.24>
/ 00:25.42
NumSongs = 5 / PlayList song limit = 12
songList[0] = <Title: Hotline Bling, Artist: Drake, Album: Hotline Bing - Single, Track Length: 00:04.27>
songList[1] = <Title: What Do You Mean?, Artist: Justin Bieber, Album: What Do You Mean? - Single, Track Length: 00:03.27>
songList[2] = <Title: Can't Feel My Face, Artist: The Weeknd, Album: Beauty Behind the Madness, Track Length: 00:03.33>
songList[3] = <Title: Good for You, Artist: Selena Gomez ft. A$AP Rocky, Album: Good for You - Single, Track Length: 00:03.41>
songList[4] = <Title: If You, Artist: Big Bang, Album: MADE, Track Length: 00:04.24>
/ 00:19.32