Use ImmutableList, add guava dependency

app/build.gradle

@@ -25,6 +25,7 @@ dependencies {
     // This dependency is used by the application.
     implementation("net.dv8tion:JDA:5.0.0-alpha.19")
     implementation 'se.michaelthelin.spotify:spotify-web-api-java:8.3.4'
+    implementation("com.google.guava:guava:33.0.0-jre")
 }
 
 task fatJar(type: Jar) {

app/src/main/java/musicbot/SpotifyClient.java

@@ -20,6 +20,7 @@ import java.io.IOException;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Optional;
+import java.util.stream.Collector;
 import java.util.stream.Collectors;
 
 public class SpotifyClient {
@@ -56,7 +57,7 @@ public class SpotifyClient {
 
       final Paging<Track> tracks = searchTracksRequest.execute();
 
-      return Arrays.stream(tracks.getItems()).collect(Collectors.toList());
+      return Arrays.stream(tracks.getItems()).collect(ImmutableList.toImmutableList());
     } catch (SpotifyWebApiException | ParseException | IOException exception) {
       return List.of();
     }
@@ -80,7 +81,7 @@ public class SpotifyClient {
     try {
       final Recommendations recommendations = recommendationsRequest.execute();
 
-      return Arrays.stream(recommendations.getTracks()).collect(Collectors.toList());
+      return Arrays.stream(recommendations.getTracks()).collect(ImmutableList.toImmutableList());
     } catch (IOException | SpotifyWebApiException | ParseException e) {
       System.out.println("Error: " + e.getMessage());
       return ImmutableList.of();
@@ -92,7 +93,7 @@ public class SpotifyClient {
 
     try {
       final String[] genres = request.execute();
-      return Arrays.stream(genres).collect(Collectors.toList());
+      return Arrays.stream(genres).collect(ImmutableList.toImmutableList());
     } catch (IOException | SpotifyWebApiException | ParseException e) {
       System.out.println("Error: " + e.getMessage());
       return ImmutableList.of();

app/src/main/java/musicbot/buttonInteractions/MoreRecommendation.java

@@ -1,5 +1,6 @@
 package musicbot.buttonInteractions;
 
+import com.google.common.collect.ImmutableList;
 import musicbot.ButtonInteraction;
 import musicbot.Paginator;
 import musicbot.RecommendationService;
@@ -54,7 +55,7 @@ public class MoreRecommendation implements ButtonInteraction {
       trackList.forEach(track -> {
         final List<String> trackArtists = Arrays.stream(track.getArtists())
             .map(ArtistSimplified::getName)
-            .collect(Collectors.toList());
+            .collect(ImmutableList.toImmutableList());
         final String artists = String.join(", ", trackArtists);
 
         eb.addField(track.getName(), artists, false);
@@ -67,7 +68,7 @@ public class MoreRecommendation implements ButtonInteraction {
             .collect(Collectors.joining(", "));
 
         return Button.primary("recommend_" + artists, track.getName());
-      }).collect(Collectors.toList());
+      }).collect(ImmutableList.toImmutableList());
 
       if (!paginatedTracks.isIsLastPage()) {
         final String buttonId = "more-recommend_" + artist + "--" + genre + "_" + paginatedTracks.getNextPageNum();

app/src/main/java/musicbot/commands/Recommend.java

@@ -1,5 +1,6 @@
 package musicbot.commands;
 
+import com.google.common.collect.ImmutableList;
 import musicbot.MCommand;
 import musicbot.Paginator;
 import musicbot.RecommendationService;
@@ -65,7 +66,7 @@ public class Recommend implements MCommand {
       trackList.forEach(track -> {
         final List<String> trackArtists = Arrays.stream(track.getArtists())
             .map(ArtistSimplified::getName)
-            .collect(Collectors.toList());
+            .collect(ImmutableList.toImmutableList());
         final String artists = String.join(", ", trackArtists);
 
         eb.addField(track.getName(), artists, false);
@@ -77,7 +78,7 @@ public class Recommend implements MCommand {
             .collect(Collectors.joining(", "));
 
         return Button.primary("recommend_" + artists, track.getName());
-      }).collect(Collectors.toList());
+      }).collect(ImmutableList.toImmutableList());
 
       final String buttonId = "more-recommend_" + artistInput + "--" + genreInput + "_" + paginatedTracks.getNextPageNum();