Added checkstyle and fixed issues in classes.

Author: andrewlalis

.gitignore

@@ -1,4 +1,4 @@
 .idea/
 .gradle/
 build/
-/config/
+/javabot_config/

build.gradle

@@ -1,5 +1,6 @@
 plugins {
     id 'java'
+    id 'checkstyle'
 }
 
 group 'net.javadiscord'
@@ -16,7 +17,7 @@ dependencies {
     implementation 'org.javacord:javacord:3.3.2'
 
     implementation 'org.yaml:snakeyaml:1.29'
-    implementation 'com.google.code.gson:gson:2.8.8'
+    implementation 'com.google.code.gson:gson:2.8.9'
 
     // Persistence Dependencies
     implementation 'org.mongodb:mongodb-driver:3.12.10'
@@ -45,4 +46,9 @@ jar {
 
 test {
     useJUnitPlatform()
+}
+
+checkstyle {
+    toolVersion '9.1'
+    configDirectory.set(new File("checkstyle"))
 }

checkstyle/checkstyle.xml

@@ -0,0 +1,84 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE module PUBLIC
+        "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
+        "https://checkstyle.org/dtds/configuration_1_3.dtd">
+<module name="Checker">
+    <module name="TreeWalker">
+        <property name="fileExtensions" value="java"/>
+        <module name="ArrayTypeStyle"/>
+
+        <!-- Javadoc Checks -->
+        <module name="AtclauseOrder"/>
+        <module name="NonEmptyAtclauseDescription"/>
+        <module name="JavadocStyle"/>
+        <module name="SummaryJavadocCheck"/>
+        <module name="JavadocMethod"/>
+        <module name="JavadocType"/>
+        <module name="MissingJavadocType">
+            <property name="scope" value="protected"/>
+        </module>
+        <module name="MissingJavadocMethod">
+            <property name="scope" value="protected"/>
+            <property name="allowMissingPropertyJavadoc" value="true"/>
+            <property name="minLineCount" value="2"/>
+        </module>
+        <module name="JavadocVariable">
+            <property name="scope" value="protected"/>
+        </module>
+        <module name="JavadocContentLocationCheck"/>
+        <module name="JavadocBlockTagLocation"/>
+        <module name="JavadocMissingLeadingAsterisk"/>
+        <module name="JavadocMissingWhitespaceAfterAsterisk"/>
+
+        <!-- Code Quality -->
+        <module name="EmptyBlock"/>
+        <module name="LeftCurly"/>
+        <module name="NeedBraces">
+            <property name="allowSingleLineStatement" value="true"/>
+        </module>
+        <module name="RightCurly"/>
+        <module name="DeclarationOrder"/>
+        <module name="FallThrough"/>
+        <module name="IllegalCatch"/>
+        <module name="IllegalThrows"/>
+        <module name="IllegalToken"/>
+        <module name="IllegalType"/>
+        <module name="InnerAssignment"/>
+        <module name="MagicNumber"/>
+        <module name="MultipleStringLiterals">
+            <property name="allowedDuplicates" value="3"/>
+        </module>
+        <module name="MultipleVariableDeclarations"/>
+        <module name="NoClone"/>
+        <module name="OneStatementPerLine"/>
+        <module name="PackageDeclaration"/>
+        <module name="ReturnCount">
+            <property name="max" value="5"/>
+            <property name="maxForVoid" value="8"/>
+        </module>
+        <module name="SimplifyBooleanExpression"/>
+        <module name="SimplifyBooleanReturn"/>
+        <module name="StringLiteralEquality"/>
+        <module name="UnnecessaryParentheses"/>
+        <module name="UnnecessarySemicolonAfterOuterTypeDeclaration"/>
+        <module name="UnnecessarySemicolonAfterTypeMemberDeclaration"/>
+        <module name="UnnecessarySemicolonInEnumeration"/>
+        <module name="UnnecessarySemicolonInTryWithResources"/>
+        <module name="InnerTypeLast"/>
+        <module name="HideUtilityClassConstructor"/>
+        <module name="InterfaceIsType"/>
+        <module name="MutableException"/>
+        <module name="OneTopLevelClass"/>
+        <module name="ModifierOrder"/>
+        <module name="RedundantModifier"/>
+        <!-- Custom regex for finding space indentation violations. -->
+        <module name="RegexpSinglelineJava">
+            <property name="format" value="^\t* +\t*\S"/>
+            <property name="message" value="Line has leading space characters; indentation should be performed with tabs only."/>
+            <property name="ignoreComments" value="true"/>
+        </module>
+        <module name="MethodLength">
+            <property name="max" value="50"/>
+        </module>
+    </module>
+</module>

checkstyle/suppressions.xml

@@ -37,6 +37,13 @@ public class Bot {
 	 */
 	public static ScheduledExecutorService asyncPool;
 
+	// Hide constructor.
+	private Bot() {}
+
+	/**
+	 * Starts the bot.
+	 * @param args Command-line arguments.
+	 */
 	public static void main(String[] args) {
 		initDataSources();
 		asyncPool = Executors.newScheduledThreadPool(config.getSystems().getAsyncPoolSize());
@@ -56,7 +63,7 @@ public static void main(String[] args) {
 	 * with the Discord API.
 	 */
 	private static void initDataSources() {
-		config = new BotConfig(Path.of("config"));
+		config = new BotConfig(Path.of("javabot_config"));
 		if (config.getSystems().getDiscordBotToken() == null || config.getSystems().getDiscordBotToken().isBlank()) {
 			throw new IllegalStateException("Missing required Discord bot token! Please edit config/systems.json to add it, then run again.");
 		}

src/main/java/net/javadiscord/javabot2/Bot.java

@@ -11,17 +11,37 @@
  * advantage of throwing an exception up the call stack.
  */
 public class ResponseException extends Exception {
+	/**
+	 * The response builder that's used to respond to an interaction in the case
+	 * of an exception.
+	 */
 	@Getter
 	private final InteractionImmediateResponseBuilder responseBuilder;
 
+	/**
+	 * Constructs the exception.
+	 * @param responseBuilder The response builder to use.
+	 */
 	public ResponseException(InteractionImmediateResponseBuilder responseBuilder) {
 		this.responseBuilder = responseBuilder;
 	}
 
+	/**
+	 * Gets a supplier that supplies a response exception with a warning
+	 * response. This is especially useful with {@link java.util.Optional#orElseThrow(Supplier)}.
+	 * @param message The warning message.
+	 * @return The exception supplier.
+	 */
 	public static Supplier<ResponseException> warning(String message) {
 		return () -> new ResponseException(Responses.deferredWarningBuilder().message(message).build());
 	}
 
+	/**
+	 * Gets a supplier that supplies a response exception with an error
+	 * response. This is especially useful with {@link java.util.Optional#orElseThrow(Supplier)}.
+	 * @param message The error message.
+	 * @return The exception supplier.
+	 */
 	public static Supplier<ResponseException> error(String message) {
 		return () -> new ResponseException(Responses.deferredErrorBuilder().message(message).build());
 	}

src/main/java/net/javadiscord/javabot2/command/ResponseException.java

@@ -14,6 +14,8 @@
  * Provides methods for standardized replies to interaction events.
  */
 public class Responses {
+	private Responses() {}
+
 	public static InteractionImmediateResponseBuilder success(InteractionBase interaction, String title, String message) {
 		return reply(interaction, title, message, Color.GREEN, true);
 	}
@@ -112,35 +114,69 @@ private ResponseBuilder(Color color) {
 			this(null, color);
 		}
 
+		/**
+		 * Sets the title of the response.
+		 * @param title The title to show.
+		 * @return The response builder.
+		 */
 		public ResponseBuilder title(String title) {
 			this.title = title;
 			return this;
 		}
 
+		/**
+		 * Sets the message of the response.
+		 * @param message The message to show.
+		 * @return The response builder.
+		 */
 		public ResponseBuilder message(String message) {
 			this.message = message;
 			return this;
 		}
 
+		/**
+		 * Makes this response publicly visible, i.e. not ephemeral.
+		 * @return The response builder.
+		 */
 		public ResponseBuilder makePublic() {
 			this.ephemeral = false;
 			return this;
 		}
 
+		/**
+		 * Builds a Javacord response builder.
+		 * @return A Javacord response builder.
+		 */
 		public InteractionImmediateResponseBuilder build() {
 			return reply(interaction, title, message, color, ephemeral);
 		}
 
+		/**
+		 * Builds a Javacord response builder using the given interaction.
+		 * @param interaction The interaction that will be responded to.
+		 * @return A Javacord response builder.
+		 */
 		public InteractionImmediateResponseBuilder build(InteractionBase interaction) {
 			this.interaction = interaction;
 			return build();
 		}
 
+		/**
+		 * Sends a Javacord response to the given interaction, using this
+		 * builder's settings.
+		 * @param interaction The interaction to send the response to.
+		 * @return A future that completes once the response is sent.
+		 */
 		public CompletableFuture<InteractionOriginalResponseUpdater> respond(InteractionBase interaction) {
 			this.interaction = interaction;
 			return build().respond();
 		}
 
+		/**
+		 * Sends a Javacord response as a reply to this builder's configured
+		 * interaction.
+		 * @return A future that completes once the response is sent.
+		 */
 		public CompletableFuture<InteractionOriginalResponseUpdater> respond() {
 			return this.build().respond();
 		}

src/main/java/net/javadiscord/javabot2/command/Responses.java

@@ -8,5 +8,11 @@
  * handler in any command configuration file.
  */
 public interface SlashCommandHandler {
-	InteractionImmediateResponseBuilder handle(SlashCommandInteraction interaction) throws Exception;
+	/**
+	 * Handles a slash command interaction.
+	 * @param interaction The interaction.
+	 * @return An immediate response to the interaction.
+	 * @throws ResponseException If an error occurs while handling the event.
+	 */
+	InteractionImmediateResponseBuilder handle(SlashCommandInteraction interaction) throws ResponseException;
 }

src/main/java/net/javadiscord/javabot2/command/SlashCommandHandler.java

@@ -20,6 +20,9 @@
  */
 @Slf4j
 public final class SlashCommandListener implements SlashCommandCreateListener {
+	/**
+	 * The set of all slash command handlers, mapped by their ids.
+	 */
 	private final Map<Long, SlashCommandHandler> commandHandlers = new HashMap<>();
 
 	/**
@@ -42,11 +45,6 @@ public void onSlashCommandCreate(SlashCommandCreateEvent event) {
 				handler.handle(event.getSlashCommandInteraction()).respond();
 			} catch (ResponseException e) {
 				e.getResponseBuilder().respond();
-			} catch (Exception e) {
-				log.error("An error occurred while handling a slash command.", e);
-				Responses.errorBuilder(event)
-						.message("An error occurred while executing the command.")
-						.respond();
 			}
 		} else {
 			Responses.warningBuilder(event)
@@ -85,7 +83,7 @@ private Map<String, SlashCommandHandler> initializeHandlers(CommandConfig[] comm
 				try {
 					Class<?> handlerClass = Class.forName(commandConfig.getHandler());
 					handlers.put(commandConfig.getName(), (SlashCommandHandler) handlerClass.getConstructor().newInstance());
-				} catch (Exception e) {
+				} catch (ReflectiveOperationException e) {
 					log.error("An error occurred when trying to get new instance of a slash command handler class.", e);
 				}
 			} else {

src/main/java/net/javadiscord/javabot2/command/SlashCommandListener.java

@@ -20,6 +20,10 @@ public class CommandConfig {
 	private SubCommandGroupConfig[] subCommandGroups;
 	private String handler;
 
+	/**
+	 * Converts this config data into data that's ready for the Discord API.
+	 * @return The prepared data.
+	 */
 	public SlashCommandBuilder toData() {
 		var builder = new SlashCommandBuilder()
 				.setName(this.name)