add some javadocs and minor cleanup

app/src/main/java/musicbot/ButtonInteraction.java

@@ -2,8 +2,19 @@ package musicbot;
 
 import net.dv8tion.jda.api.events.interaction.component.ButtonInteractionEvent;
 
+/**
+ * Interface to build a button interaction to manage a button event
+ */
 public interface ButtonInteraction {
+  /**
+   * A unique name that identifies the button interaction
+   * @return String the name of the button
+   */
   String getName();
 
+  /**
+   * Executes the interaction logic of the button
+   * @param event
+   */
   void execute(ButtonInteractionEvent event);
 }

app/src/main/java/musicbot/ButtonInteractionManager.java

@@ -7,9 +7,18 @@ import org.jetbrains.annotations.NotNull;
 import java.util.ArrayList;
 import java.util.List;
 
+/**
+ * Extension of the Listener Adaptor that manages all the interactions. Because
+ * JDA doesn't have a class to specifically build button events, this is a custom way
+ * of doing so.
+ */
 public class ButtonInteractionManager extends ListenerAdapter {
   private final List<ButtonInteraction> buttonInteractions = new ArrayList<>();
 
+  /**
+   * Listener for the button interactions.
+   * @param event the {@code ButtonInteractionEvent}
+   */
   @Override
   public void onButtonInteraction(@NotNull ButtonInteractionEvent event) {
     final String id = event.getComponent().getId();
@@ -23,6 +32,10 @@ public class ButtonInteractionManager extends ListenerAdapter {
     }
   }
 
+  /**
+   * Add a ButtonInteraction to the ButtonInteractionManager
+   * @param buttonInteraction the ButtonInteractiont to be added
+   */
   public void add(@NotNull final ButtonInteraction buttonInteraction) {
     buttonInteractions.add(buttonInteraction);
   }

app/src/main/java/musicbot/CommandManager.java

@@ -9,6 +9,9 @@ import org.jetbrains.annotations.NotNull;
 import java.util.ArrayList;
 import java.util.List;
 
+/**
+ * Extension of the Listener Adaptor that manages all the commands.
+ */
 public class CommandManager extends ListenerAdapter {
   private final List<MCommand> commands = new ArrayList<>();
 

app/src/main/java/musicbot/MCommand.java

@@ -5,6 +5,11 @@ import net.dv8tion.jda.api.interactions.commands.build.OptionData;
 
 import java.util.List;
 
+/**
+ * Interface to build a command interaction to manage a button event.
+ * This class is prefaced with an M (for MusicBot) as to not confuse with
+ * JDA's Command class.
+ */
 public interface MCommand {
   String getName();
 

app/src/main/java/musicbot/YoutubeSearch.java

@@ -19,8 +19,6 @@ import java.util.Optional;
 import java.util.Properties;
 
 public class YoutubeSearch {
-  private static final String PROPERTIES_FILENAME = "youtube.properties";
-
   private static final HttpTransport HTTP_TRANSPORT = new NetHttpTransport();
 
   private static final JsonFactory JSON_FACTORY = new JacksonFactory();

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

@@ -13,6 +13,10 @@ import java.util.Arrays;
 import java.util.List;
 import java.util.stream.Collectors;
 
+/**
+ * This interaction happens when a user requests more recommendations
+ * after initial /recommend.
+ */
 public class MoreRecommendation implements ButtonInteraction {
   private static final int INCREMENT = 5;
   private static final String ARGS_DELIMITER = "_";

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

@@ -5,7 +5,6 @@ import musicbot.RecommendationService;
 import net.dv8tion.jda.api.EmbedBuilder;
 import net.dv8tion.jda.api.entities.MessageEmbed;
 import net.dv8tion.jda.api.events.interaction.command.SlashCommandInteractionEvent;
-import net.dv8tion.jda.api.interactions.commands.OptionMapping;
 import net.dv8tion.jda.api.interactions.commands.OptionType;
 import net.dv8tion.jda.api.interactions.commands.build.OptionData;
 import net.dv8tion.jda.api.interactions.components.buttons.Button;
@@ -74,10 +73,8 @@ public class Recommend implements MCommand {
 
 
       final List<Button> buttons = trackList.stream().map(track -> {
-            final String artists = String.join(
-                ", ",
-                Arrays.stream(track.getArtists()).map(ArtistSimplified::getName)
-                    .collect(Collectors.toList()));
+            final String artists = Arrays.stream(track.getArtists()).map(ArtistSimplified::getName)
+                .collect(Collectors.joining(", "));
 
             return Button.primary("recommend_" + artists, track.getName());
       }).collect(Collectors.toList());