Full Checkstyle compliance at last.

proxy/src/main/java/com/velocitypowered/proxy/VelocityServer.java

@@ -104,18 +104,11 @@ public class VelocityServer implements ProxyServer {
   }
 
   public KeyPair getServerKeyPair() {
-    if (serverKeyPair == null) {
-      throw new AssertionError();
-    }
-    return serverKeyPair;
+    return ensureInitialized(serverKeyPair);
   }
 
   public VelocityConfiguration getConfiguration() {
-    VelocityConfiguration cfg = this.configuration;
-    if (cfg == null) {
-      throw new IllegalStateException("Configuration not initialized!");
-    }
-    return cfg;
+    return ensureInitialized(this.configuration);
   }
 
   @Override
@@ -250,6 +243,12 @@ public class VelocityServer implements ProxyServer {
     return shutdown;
   }
 
+  /**
+   * Reloads the proxy's configuration.
+   *
+   * @return {@code true} if successful, {@code false} if we can't read the configuration
+   * @throws IOException if we can't read {@code velocity.toml}
+   */
   public boolean reloadConfiguration() throws IOException {
     Path configPath = Paths.get("velocity.toml");
     VelocityConfiguration newConfiguration = VelocityConfiguration.read(configPath);
@@ -331,6 +330,11 @@ public class VelocityServer implements ProxyServer {
     return true;
   }
 
+  /**
+   * Shuts down the proxy.
+   *
+   * @param explicitExit whether the user explicitly shut down the proxy
+   */
   public void shutdown(boolean explicitExit) {
     if (eventManager == null || pluginManager == null || cm == null || scheduler == null) {
       throw new AssertionError();
@@ -365,19 +369,25 @@ public class VelocityServer implements ProxyServer {
   }
 
   public NettyHttpClient getHttpClient() {
-    if (httpClient == null) {
-      throw new IllegalStateException("HTTP client not initialized");
-    }
-    return httpClient;
+    return ensureInitialized(httpClient);
   }
 
   public Ratelimiter getIpAttemptLimiter() {
-    if (ipAttemptLimiter == null) {
-      throw new IllegalStateException("Ratelimiter not initialized");
-    }
-    return ipAttemptLimiter;
+    return ensureInitialized(ipAttemptLimiter);
   }
 
+  private static <T> T ensureInitialized(T o) {
+    if (o == null) {
+      throw new IllegalStateException("The proxy isn't fully initialized.");
+    }
+    return o;
+  }
+
+  /**
+   * Attempts to register the {@code connection} with the proxy.
+   * @param connection the connection to register
+   * @return {@code true} if we registered the connection, {@code false} if not
+   */
   public boolean registerConnection(ConnectedPlayer connection) {
     String lowerName = connection.getUsername().toLowerCase(Locale.US);
     if (connectionsByName.putIfAbsent(lowerName, connection) != null) {

proxy/src/main/java/com/velocitypowered/proxy/config/VelocityConfiguration.java

@@ -266,6 +266,11 @@ public class VelocityConfiguration extends AnnotatedConfig implements ProxyConfi
     return motd;
   }
 
+  /**
+   * Returns the proxy's MOTD.
+   *
+   * @return the MOTD
+   */
   public Component getMotdComponent() {
     if (motdAsComponent == null) {
       if (motd.startsWith("{")) {

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/BackendPlaySessionHandler.java

@@ -95,7 +95,8 @@ public class BackendPlaySessionHandler implements MinecraftSessionHandler {
     }
 
     if (PluginMessageUtil.isMcBrand(packet)) {
-      PluginMessage rewritten = PluginMessageUtil.rewriteMinecraftBrand(packet, server.getVersion());
+      PluginMessage rewritten = PluginMessageUtil.rewriteMinecraftBrand(packet,
+          server.getVersion());
       serverConn.getPlayer().getConnection().write(rewritten);
       return true;
     }

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/VelocityServerConnection.java

@@ -212,6 +212,9 @@ public class VelocityServerConnection implements MinecraftConnectionAssociation,
     return true;
   }
 
+  /**
+   * Indicates that we have completed the plugin process.
+   */
   public void completeJoin() {
     if (!hasCompletedJoin) {
       hasCompletedJoin = true;

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ClientPlaySessionHandler.java

@@ -296,6 +296,11 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
     }
   }
 
+  /**
+   * Handles the {@code JoinGame} packet. This function is responsible for handling the client-side
+   * switching servers in Velocity.
+   * @param joinGame the join game packet
+   */
   public void handleBackendJoinGame(JoinGame joinGame) {
     VelocityServerConnection serverConn = player.getConnectedServer();
     if (serverConn == null) {
@@ -387,6 +392,11 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
     return knownChannels;
   }
 
+  /**
+   * Handles additional tab complete for 1.12 and lower clients.
+   *
+   * @param response the tab complete response from the backend
+   */
   public void handleTabCompleteResponse(TabCompleteResponse response) {
     if (outstandingTabComplete != null) {
       if (!outstandingTabComplete.isAssumeCommand()

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ConnectedPlayer.java

@@ -296,6 +296,11 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player {
     connectionInFlight = null;
   }
 
+  /**
+   * Handles unexpected disconnects.
+   * @param server the server we disconnected from
+   * @param throwable the exception
+   */
   public void handleConnectionException(RegisteredServer server, Throwable throwable) {
     if (throwable == null) {
       throw new NullPointerException("throwable");
@@ -321,6 +326,11 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player {
     handleConnectionException(server, null, TextComponent.of(userMessage, TextColor.RED));
   }
 
+  /**
+   * Handles unexpected disconnects.
+   * @param server the server we disconnected from
+   * @param disconnect the disconnect packet
+   */
   public void handleConnectionException(RegisteredServer server, Disconnect disconnect) {
     Component disconnectReason = ComponentSerializers.JSON.deserialize(disconnect.getReason());
     String plainTextReason = PASS_THRU_TRANSLATE.serialize(disconnectReason);
@@ -382,6 +392,11 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player {
     }
   }
 
+  /**
+   * Finds another server to attempt to log into, if we were unexpectedly disconnected from the
+   * server.
+   * @return the next server to try
+   */
   public Optional<RegisteredServer> getNextServerToTry() {
     if (serversToTry == null) {
       String virtualHostStr = getVirtualHost().map(InetSocketAddress::getHostString).orElse("");
@@ -402,6 +417,11 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player {
     return server.getServer(toTryName);
   }
 
+  /**
+   * Sets the player's new connected server and clears the in-flight connection.
+   *
+   * @param serverConnection the new server connection
+   */
   public void setConnectedServer(@Nullable VelocityServerConnection serverConnection) {
     this.connectedServer = serverConnection;
     this.tryIndex = 0; // reset since we got connected to a server

proxy/src/main/java/com/velocitypowered/proxy/console/VelocityConsole.java

@@ -1,13 +1,12 @@
 package com.velocitypowered.proxy.console;
 
-import static com.velocitypowered.api.permission.PermissionFunction.*;
+import static com.velocitypowered.api.permission.PermissionFunction.ALWAYS_TRUE;
 
 import com.velocitypowered.api.event.permission.PermissionsSetupEvent;
 import com.velocitypowered.api.permission.PermissionFunction;
 import com.velocitypowered.api.permission.Tristate;
 import com.velocitypowered.api.proxy.ConsoleCommandSource;
 import com.velocitypowered.proxy.VelocityServer;
-import java.io.PrintWriter;
 import java.util.List;
 import net.kyori.text.Component;
 import net.kyori.text.TextComponent;
@@ -44,11 +43,17 @@ public final class VelocityConsole extends SimpleTerminalConsole implements Cons
     return this.permissionFunction.getPermissionValue(permission);
   }
 
+  /**
+   * Sets up {@code System.out} and {@code System.err} to redirect to log4j.
+   */
   public void setupStreams() {
     System.setOut(IoBuilder.forLogger(logger).setLevel(Level.INFO).buildPrintStream());
     System.setErr(IoBuilder.forLogger(logger).setLevel(Level.ERROR).buildPrintStream());
   }
 
+  /**
+   * Sets up permissions for the console.
+   */
   public void setupPermissions() {
     PermissionsSetupEvent event = new PermissionsSetupEvent(this, s -> ALWAYS_TRUE);
     // we can safely block here, this is before any listeners fire

proxy/src/main/java/com/velocitypowered/proxy/network/ConnectionManager.java

@@ -36,6 +36,11 @@ public final class ConnectionManager {
 
   private final DnsAddressResolverGroup resolverGroup;
 
+  /**
+   * Initalizes the {@code ConnectionManager}.
+   *
+   * @param server a reference to the Velocity server
+   */
   public ConnectionManager(VelocityServer server) {
     this.server = server;
     this.transportType = TransportType.bestType();
@@ -52,6 +57,11 @@ public final class ConnectionManager {
         Natives.compress.getLoadedVariant(), Natives.cipher.getLoadedVariant());
   }
 
+  /**
+   * Binds a Minecraft listener to the specified {@code address}.
+   *
+   * @param address the address to bind to
+   */
   public void bind(final InetSocketAddress address) {
     final ServerBootstrap bootstrap = new ServerBootstrap()
         .channel(this.transportType.serverSocketChannelClass)
@@ -73,6 +83,12 @@ public final class ConnectionManager {
         });
   }
 
+  /**
+   * Binds a GS4 listener to the specified {@code hostname} and {@code port}.
+   *
+   * @param hostname the hostname to bind to
+   * @param port the port to bind to
+   */
   public void queryBind(final String hostname, final int port) {
     InetSocketAddress address = new InetSocketAddress(hostname, port);
     final Bootstrap bootstrap = new Bootstrap()
@@ -92,6 +108,11 @@ public final class ConnectionManager {
         });
   }
 
+  /**
+   * Creates a TCP {@link Bootstrap} using Velocity's event loops.
+   *
+   * @return a new {@link Bootstrap}
+   */
   public Bootstrap createWorker() {
     return new Bootstrap()
         .channel(this.transportType.socketChannelClass)
@@ -102,6 +123,11 @@ public final class ConnectionManager {
         .resolver(this.resolverGroup);
   }
 
+  /**
+   * Closes the specified {@code oldBind} endpoint.
+   *
+   * @param oldBind the endpoint to close
+   */
   public void close(InetSocketAddress oldBind) {
     Channel serverChannel = endpoints.remove(oldBind);
     Preconditions.checkState(serverChannel != null, "Endpoint %s not registered", oldBind);
@@ -109,6 +135,9 @@ public final class ConnectionManager {
     serverChannel.close().syncUninterruptibly();
   }
 
+  /**
+   * Closes all endpoints.
+   */
   public void shutdown() {
     for (final Channel endpoint : this.endpoints.values()) {
       try {

proxy/src/main/java/com/velocitypowered/proxy/network/http/NettyHttpClient.java

@@ -27,6 +27,11 @@ public class NettyHttpClient {
   private final ChannelPoolMap<InetSocketAddress, SimpleChannelPool> poolMap;
   private final String userAgent;
 
+  /**
+   * Initializes the HTTP client.
+   *
+   * @param server the Velocity server
+   */
   public NettyHttpClient(VelocityServer server) {
     this.userAgent = server.getVersion().getName() + "/" + server.getVersion().getVersion();
     Bootstrap bootstrap = server.initializeGenericBootstrap();

proxy/src/main/java/com/velocitypowered/proxy/plugin/VelocityEventManager.java

@@ -44,6 +44,11 @@ public class VelocityEventManager implements EventManager {
   private final ExecutorService service;
   private final PluginManager pluginManager;
 
+  /**
+   * Initializes the Velocity event manager.
+   *
+   * @param pluginManager a reference to the Velocity plugin manager
+   */
   public VelocityEventManager(PluginManager pluginManager) {
     // Expose the event executors to the plugins - required in order for the generated ASM classes
     // to work.

proxy/src/main/java/com/velocitypowered/proxy/plugin/VelocityPluginManager.java

@@ -46,6 +46,11 @@ public class VelocityPluginManager implements PluginManager {
     }
   }
 
+  /**
+   * Loads all plugins from the specified {@code directory}.
+   * @param directory the directory to load from
+   * @throws IOException if we could not open the directory
+   */
   public void loadPlugins(Path directory) throws IOException {
     checkNotNull(directory, "directory");
     checkArgument(directory.toFile().isDirectory(), "provided path isn't a directory");

proxy/src/main/java/com/velocitypowered/proxy/plugin/loader/VelocityPluginDescription.java

@@ -25,6 +25,17 @@ public class VelocityPluginDescription implements PluginDescription {
   private final Map<String, PluginDependency> dependencies;
   private final Path source;
 
+  /**
+   * Creates a new plugin description.
+   * @param id the ID
+   * @param name the name of the plugin
+   * @param version the plugin version
+   * @param description a description of the plugin
+   * @param url the website for the plugin
+   * @param authors the authors of this plugin
+   * @param dependencies the dependencies for this plugin
+   * @param source the original source for the plugin
+   */
   public VelocityPluginDescription(String id, @Nullable String name, @Nullable String version,
       @Nullable String description, @Nullable String url,
       @Nullable List<String> authors, Collection<PluginDependency> dependencies, Path source) {

proxy/src/main/java/com/velocitypowered/proxy/plugin/util/PluginDependencyUtils.java

@@ -35,7 +35,8 @@ public class PluginDependencyUtils {
         .allowsSelfLoops(false)
         .expectedNodeCount(candidates.size())
         .build();
-    Map<String, PluginDescription> candidateMap = Maps.uniqueIndex(candidates, PluginDescription::getId);
+    Map<String, PluginDescription> candidateMap = Maps.uniqueIndex(candidates,
+        PluginDescription::getId);
 
     for (PluginDescription description : candidates) {
       graph.addNode(description);

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftDecoder.java

@@ -17,6 +17,11 @@ public class MinecraftDecoder extends MessageToMessageDecoder<ByteBuf> {
   private StateRegistry state;
   private StateRegistry.PacketRegistry.ProtocolRegistry registry;
 
+  /**
+   * Creates a new {@code MinecraftDecoder} decoding packets from the specified {@code direction}.
+   *
+   * @param direction the direction from which we decode from
+   */
   public MinecraftDecoder(ProtocolUtils.Direction direction) {
     this.direction = Preconditions.checkNotNull(direction, "direction");
     this.registry = direction

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftEncoder.java

@@ -15,6 +15,11 @@ public class MinecraftEncoder extends MessageToByteEncoder<MinecraftPacket> {
   private StateRegistry state;
   private StateRegistry.PacketRegistry.ProtocolRegistry registry;
 
+  /**
+   * Creates a new {@code MinecraftEncoder} encoding packets for the specified {@code direction}.
+   *
+   * @param direction the direction to encode to
+   */
   public MinecraftEncoder(ProtocolUtils.Direction direction) {
     this.direction = Preconditions.checkNotNull(direction, "direction");
     this.registry = direction

proxy/src/main/java/com/velocitypowered/proxy/scheduler/VelocityScheduler.java

@@ -1,5 +1,8 @@
 package com.velocitypowered.proxy.scheduler;
 
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Multimap;
@@ -29,6 +32,11 @@ public class VelocityScheduler implements Scheduler {
   private final Multimap<Object, ScheduledTask> tasksByPlugin = Multimaps.synchronizedMultimap(
       Multimaps.newSetMultimap(new IdentityHashMap<>(), HashSet::new));
 
+  /**
+   * Initalizes the scheduler.
+   *
+   * @param pluginManager the Velocity plugin manager
+   */
   public VelocityScheduler(PluginManager pluginManager) {
     this.pluginManager = pluginManager;
     this.taskService = Executors.newCachedThreadPool(new ThreadFactoryBuilder().setDaemon(true)
@@ -40,13 +48,17 @@ public class VelocityScheduler implements Scheduler {
 
   @Override
   public TaskBuilder buildTask(Object plugin, Runnable runnable) {
-    Preconditions.checkNotNull(plugin, "plugin");
-    Preconditions.checkNotNull(runnable, "runnable");
-    Preconditions
-        .checkArgument(pluginManager.fromInstance(plugin).isPresent(), "plugin is not registered");
+    checkNotNull(plugin, "plugin");
+    checkNotNull(runnable, "runnable");
+    checkArgument(pluginManager.fromInstance(plugin).isPresent(), "plugin is not registered");
     return new TaskBuilderImpl(plugin, runnable);
   }
 
+  /**
+   * Shuts down the Velocity scheduler.
+   * @return {@code true} if all tasks finished, {@code false} otherwise
+   * @throws InterruptedException if the current thread was interrupted
+   */
   public boolean shutdown() throws InterruptedException {
     Collection<ScheduledTask> terminating;
     synchronized (tasksByPlugin) {
@@ -121,7 +133,7 @@ public class VelocityScheduler implements Scheduler {
       this.repeat = repeat;
     }
 
-    public void schedule() {
+    void schedule() {
       if (repeat == 0) {
         this.future = timerExecutionService.schedule(this, delay, TimeUnit.MILLISECONDS);
       } else {