Some final cleanups

Author: JulianVennen

CHANGELOG.md

@@ -42,10 +42,10 @@ JSON body you can use `ApiRequest#jsonBodyPublisher(Object)`. This only affects
 string or object.
 
 ### WebSockets
-The `java-websocket` library has been replaced by the built-in Java 11 websocket implementation. Unless you were using
-the `WebSocketClient` or `WebSocketManager` classes directly this shouldn't require any changes to your code.
-
-`Server#subscribe` and `Server#unsubscribe` now accept the `StreamName` enum instead of any string
+The `java-websocket` library has been replaced by the built-in Java 11 websocket implementation. Websocket connections
+are now automatically created when a subscriber is registered and closed when the last subscriber is removed. Manually
+closing a connection using `Server#unsubscribe()` is still supported. This method does not throw an exception if there
+is no connection to close.
 
 The debug/error handler methods have been removed. Errors and debug messages are now  exclusively logged using SLF4J
 

src/main/java/com/exaroton/api/APIException.java

@@ -1,11 +1,10 @@
 package com.exaroton.api;
 
+/**
+ * Exception thrown by the exaroton API.
+ */
 public class APIException extends Exception {
     public APIException(String message) {
         super(message);
     }
-
-    public APIException(String message, Throwable cause) {
-        super(message, cause);
-    }
 }

src/main/java/com/exaroton/api/BrandColor.java

@@ -1,5 +1,6 @@
 package com.exaroton.api;
 
+@SuppressWarnings("unused")
 public enum BrandColor {
     DARK(0x0f0f0f),
     LIGHT(0xffffff),

src/main/java/com/exaroton/api/server/PlayerList.java

@@ -78,10 +78,7 @@ public CompletableFuture<List<String>> add(String... entries) throws IOException
      * @throws IOException Connection errors
      */
     public CompletableFuture<List<String>> add(Collection<String> entries) throws IOException {
-        if (entries.isEmpty()) {
-            throw new IllegalArgumentException("Can't add empty list");
-        }
-
+        ParameterValidator.requireNonEmpty(entries, "entries");
         return client.request(new AddPlayerListEntriesRequest(this.client, this.gson, this.serverId, this.name, entries));
     }
 
@@ -105,10 +102,7 @@ public CompletableFuture<List<String>> remove(String... entries) throws IOExcept
      * @throws IOException Connection errors
      */
     public CompletableFuture<List<String>> remove(List<String> entries) throws IOException {
-        if (entries.isEmpty()) {
-            throw new IllegalArgumentException("Can't remove empty list");
-        }
-
+        ParameterValidator.requireNonEmpty(entries, "entries");
         return client.request(new RemovePlayerListEntriesRequest(this.client, this.gson, this.serverId, this.name, entries));
     }
 }

src/main/java/com/exaroton/api/server/Server.java

@@ -564,7 +564,8 @@ public void removeTickSubscriber(@NotNull TickSubscriber subscriber) {
 
     /**
      * Unsubscribe from websocket events. This happens automatically when there are no registered subscribers, but you
-     * might still want to call this method explicitly as a cleanup step.
+     * might still want to call this method explicitly as a cleanup step. If no connection is active, this method does
+     * nothing.
      */
     public void unsubscribe() {
         if (this.webSocket == null) {

src/main/java/com/exaroton/api/server/ServerMOTDInfo.java

@@ -1,17 +1,11 @@
 package com.exaroton.api.server;
 
-import org.jetbrains.annotations.ApiStatus;
-
+@SuppressWarnings("unused")
 public final class ServerMOTDInfo {
     /**
      * Server MOTD
      */
-    private final String motd;
-
-    @ApiStatus.Internal
-    public ServerMOTDInfo(String motd) {
-        this.motd = motd;
-    }
+    private String motd;
 
     /**
      * @return server MOTD