Mix of Checkstyle and SonarLint.

api/src/ap/java/com/velocitypowered/api/plugin/ap/PluginAnnotationProcessor.java

@@ -2,7 +2,6 @@ package com.velocitypowered.api.plugin.ap;
 
 import com.google.gson.Gson;
 import com.velocitypowered.api.plugin.Plugin;
-import com.velocitypowered.api.plugin.PluginDescription;
 import java.io.BufferedWriter;
 import java.io.IOException;
 import java.io.Writer;
@@ -66,7 +65,7 @@ public class PluginAnnotationProcessor extends AbstractProcessor {
       }
 
       Plugin plugin = element.getAnnotation(Plugin.class);
-      if (!PluginDescription.ID_PATTERN.matcher(plugin.id()).matches()) {
+      if (!SerializedPluginDescription.ID_PATTERN.matcher(plugin.id()).matches()) {
         environment.getMessager().printMessage(Diagnostic.Kind.ERROR, "Invalid ID for plugin "
             + qualifiedName
             + ". IDs must start alphabetically, have alphanumeric characters, and can "

api/src/ap/java/com/velocitypowered/api/plugin/ap/SerializedPluginDescription.java

@@ -8,11 +8,14 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Objects;
+import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
 public class SerializedPluginDescription {
 
+  public static final Pattern ID_PATTERN = Pattern.compile("[a-z][a-z0-9-_]{0,63}");
+
   // @Nullable is used here to make GSON skip these in the serialized file
   private final String id;
   private final @Nullable String name;
@@ -26,7 +29,9 @@ public class SerializedPluginDescription {
   private SerializedPluginDescription(String id, String name, String version, String description,
       String url,
       List<String> authors, List<Dependency> dependencies, String main) {
-    this.id = Preconditions.checkNotNull(id, "id");
+    Preconditions.checkNotNull(id, "id");
+    Preconditions.checkArgument(ID_PATTERN.matcher(id).matches(), "id is not valid");
+    this.id = id;
     this.name = Strings.emptyToNull(name);
     this.version = Strings.emptyToNull(version);
     this.description = Strings.emptyToNull(description);

api/src/main/java/com/velocitypowered/api/event/connection/ConnectionHandshakeEvent.java

@@ -4,7 +4,7 @@ import com.google.common.base.Preconditions;
 import com.velocitypowered.api.proxy.InboundConnection;
 
 /**
- * This event is fired when a handshake is established between a client and Velocity.
+ * This event is fired when a handshake is established between a client and the proxy.
  */
 public final class ConnectionHandshakeEvent {
 

api/src/main/java/com/velocitypowered/api/plugin/Plugin.java

@@ -14,7 +14,8 @@ public @interface Plugin {
 
   /**
    * The ID of the plugin. This ID should be unique as to not conflict with other plugins. The
-   * plugin ID must match the {@link PluginDescription#ID_PATTERN}.
+   * plugin ID may contain alphanumeric characters, dashes, and underscores, and be a maximum
+   * of 64 characters long.
    *
    * @return the ID for this plugin
    */

api/src/main/java/com/velocitypowered/api/util/title/TextTitle.java

@@ -186,21 +186,23 @@ public final class TextTitle implements Title {
       return this;
     }
 
-    public Builder stay(int ticks) {
+    private int checkTicks(int ticks) {
       Preconditions.checkArgument(ticks >= 0, "ticks value %s is negative", ticks);
-      this.stay = ticks;
+      return ticks;
+    }
+
+    public Builder stay(int ticks) {
+      this.stay = checkTicks(ticks);
       return this;
     }
 
     public Builder fadeIn(int ticks) {
-      Preconditions.checkArgument(ticks >= 0, "ticks value %s is negative", ticks);
+      this.fadeIn = checkTicks(ticks);
-      this.fadeIn = ticks;
       return this;
     }
 
     public Builder fadeOut(int ticks) {
-      Preconditions.checkArgument(ticks >= 0, "ticks value %s is negative", ticks);
+      this.fadeOut = checkTicks(ticks);
-      this.fadeOut = ticks;
       return this;
     }
 

native/src/main/java/com/velocitypowered/natives/NativeSetupException.java

@@ -0,0 +1,24 @@
+package com.velocitypowered.natives;
+
+public class NativeSetupException extends RuntimeException {
+
+  public NativeSetupException() {
+  }
+
+  public NativeSetupException(String message) {
+    super(message);
+  }
+
+  public NativeSetupException(String message, Throwable cause) {
+    super(message, cause);
+  }
+
+  public NativeSetupException(Throwable cause) {
+    super(cause);
+  }
+
+  public NativeSetupException(String message, Throwable cause, boolean enableSuppression,
+      boolean writableStackTrace) {
+    super(message, cause, enableSuppression, writableStackTrace);
+  }
+}

native/src/main/java/com/velocitypowered/natives/compression/JavaVelocityCompressor.java

@@ -1,5 +1,7 @@
 package com.velocitypowered.natives.compression;
 
+import static com.velocitypowered.natives.util.NativeConstants.ZLIB_BUFFER_SIZE;
+
 import com.google.common.base.Preconditions;
 import io.netty.buffer.ByteBuf;
 import java.util.zip.DataFormatException;

native/src/main/java/com/velocitypowered/natives/compression/NativeVelocityCompressor.java

@@ -1,5 +1,7 @@
 package com.velocitypowered.natives.compression;
 
+import static com.velocitypowered.natives.util.NativeConstants.ZLIB_BUFFER_SIZE;
+
 import com.google.common.base.Preconditions;
 import io.netty.buffer.ByteBuf;
 import java.util.zip.DataFormatException;

native/src/main/java/com/velocitypowered/natives/compression/VelocityCompressor.java

@@ -8,12 +8,6 @@ import java.util.zip.DataFormatException;
  * Provides an interface to inflate and deflate {@link ByteBuf}s using zlib.
  */
 public interface VelocityCompressor extends Disposable {
-
-  /**
-   * The default preferred output buffer size for zlib.
-   */
-  int ZLIB_BUFFER_SIZE = 8192;
-
   void inflate(ByteBuf source, ByteBuf destination) throws DataFormatException;
 
   void deflate(ByteBuf source, ByteBuf destination) throws DataFormatException;

native/src/main/java/com/velocitypowered/natives/util/NativeConstants.java

@@ -0,0 +1,12 @@
+package com.velocitypowered.natives.util;
+
+public class NativeConstants {
+  /**
+   * The default preferred output buffer size for zlib.
+   */
+  public static final int ZLIB_BUFFER_SIZE = 8192;
+
+  private NativeConstants() {
+    throw new AssertionError();
+  }
+}

native/src/main/java/com/velocitypowered/natives/util/Natives.java

@@ -1,6 +1,7 @@
 package com.velocitypowered.natives.util;
 
 import com.google.common.collect.ImmutableList;
+import com.velocitypowered.natives.NativeSetupException;
 import com.velocitypowered.natives.compression.JavaVelocityCompressor;
 import com.velocitypowered.natives.compression.NativeVelocityCompressor;
 import com.velocitypowered.natives.compression.VelocityCompressorFactory;
@@ -37,7 +38,7 @@ public class Natives {
         }));
         System.load(tempFile.toAbsolutePath().toString());
       } catch (IOException e) {
-        throw new RuntimeException(e);
+        throw new NativeSetupException("Unable to copy natives", e);
       }
     };
   }

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

@@ -91,6 +91,15 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
 
   @Override
   public boolean handle(Chat packet) {
+    VelocityServerConnection serverConnection = player.getConnectedServer();
+    if (serverConnection == null) {
+      return true;
+    }
+    MinecraftConnection smc = serverConnection.getConnection();
+    if (smc == null) {
+      return true;
+    }
+
     String msg = packet.getMessage();
     if (msg.startsWith("/")) {
       try {
@@ -106,14 +115,6 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
         return true;
       }
     } else {
-      VelocityServerConnection serverConnection = player.getConnectedServer();
-      if (serverConnection == null) {
-        return true;
-      }
-      MinecraftConnection smc = serverConnection.getConnection();
-      if (smc == null) {
-        return true;
-      }
       PlayerChatEvent event = new PlayerChatEvent(player, msg);
       server.getEventManager().fire(event)
           .thenAcceptAsync(pme -> {

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

@@ -43,9 +43,8 @@ public class JavaPluginLoader implements PluginLoader {
     }
 
     SerializedPluginDescription pd = serialized.get();
-    if (!PluginDescription.ID_PATTERN.matcher(pd.getId()).matches()) {
+    if (!SerializedPluginDescription.ID_PATTERN.matcher(pd.getId()).matches()) {
-      throw new InvalidPluginException("Plugin ID '" + pd.getId() + "' must match pattern " +
+      throw new InvalidPluginException("Plugin ID '" + pd.getId() + "' is invalid.");
-          PluginDescription.ID_PATTERN.pattern());
     }
 
     PluginClassLoader loader = new PluginClassLoader(

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/GS4QueryHandler.java

@@ -69,6 +69,25 @@ public class GS4QueryHandler extends SimpleChannelInboundHandler<DatagramPacket>
     this.server = server;
   }
 
+  private QueryResponse createInitialResponse() {
+    return QueryResponse.builder()
+        .hostname(ComponentSerializers.PLAIN
+            .serialize(server.getConfiguration().getMotdComponent()))
+        .gameVersion(ProtocolConstants.SUPPORTED_GENERIC_VERSION_STRING)
+        .map(server.getConfiguration().getQueryMap())
+        .currentPlayers(server.getPlayerCount())
+        .maxPlayers(server.getConfiguration().getShowMaxPlayers())
+        .proxyPort(server.getConfiguration().getBind().getPort())
+        .proxyHost(server.getConfiguration().getBind().getHostString())
+        .players(server.getAllPlayers().stream().map(Player::getUsername)
+            .collect(Collectors.toList()))
+        .proxyVersion("Velocity")
+        .plugins(
+            server.getConfiguration().shouldQueryShowPlugins() ? getRealPluginInformation()
+                : Collections.emptyList())
+        .build();
+  }
+
   @Override
   protected void channelRead0(ChannelHandlerContext ctx, DatagramPacket msg) throws Exception {
     ByteBuf queryMessage = msg.content();
@@ -117,22 +136,7 @@ public class GS4QueryHandler extends SimpleChannelInboundHandler<DatagramPacket>
           }
 
           // Build query response
-          QueryResponse response = QueryResponse.builder()
+          QueryResponse response = createInitialResponse();
-              .hostname(ComponentSerializers.PLAIN
-                  .serialize(server.getConfiguration().getMotdComponent()))
-              .gameVersion(ProtocolConstants.SUPPORTED_GENERIC_VERSION_STRING)
-              .map(server.getConfiguration().getQueryMap())
-              .currentPlayers(server.getPlayerCount())
-              .maxPlayers(server.getConfiguration().getShowMaxPlayers())
-              .proxyPort(server.getConfiguration().getBind().getPort())
-              .proxyHost(server.getConfiguration().getBind().getHostString())
-              .players(server.getAllPlayers().stream().map(Player::getUsername)
-                  .collect(Collectors.toList()))
-              .proxyVersion("Velocity")
-              .plugins(
-                  server.getConfiguration().shouldQueryShowPlugins() ? getRealPluginInformation()
-                      : Collections.emptyList())
-              .build();
 
           boolean isBasic = queryMessage.readableBytes() == 0;
 

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/PlayerListItem.java

@@ -50,14 +50,13 @@ public class PlayerListItem implements MinecraftPacket {
       Item item = new Item(ProtocolUtils.readUuid(buf));
       items.add(item);
       switch (action) {
-        case ADD_PLAYER: {
+        case ADD_PLAYER:
           item.setName(ProtocolUtils.readString(buf));
           item.setProperties(ProtocolUtils.readProperties(buf));
           item.setGameMode(ProtocolUtils.readVarInt(buf));
           item.setLatency(ProtocolUtils.readVarInt(buf));
           item.setDisplayName(readOptionalComponent(buf));
           break;
-        }
         case UPDATE_GAMEMODE:
           item.setGameMode(ProtocolUtils.readVarInt(buf));
           break;