diff --git a/HMCL/src/main/java/org/jackhuang/hmcl/ui/multiplayer/LocalServerBroadcaster.java b/HMCL/src/main/java/org/jackhuang/hmcl/ui/multiplayer/LocalServerBroadcaster.java
index 77b824765..bdb105a39 100644
--- a/HMCL/src/main/java/org/jackhuang/hmcl/ui/multiplayer/LocalServerBroadcaster.java
+++ b/HMCL/src/main/java/org/jackhuang/hmcl/ui/multiplayer/LocalServerBroadcaster.java
@@ -44,7 +44,12 @@ public class LocalServerBroadcaster implements AutoCloseable {
 
     public LocalServerBroadcaster(String address) {
         this.address = address;
-        this.threadGroup.setDaemon(true);
+    }
+
+    private Thread newThread(Runnable task, String name) {
+        Thread thread = new Thread(threadGroup, task, name);
+        thread.setDaemon(true);
+        return thread;
     }
 
     @Override
@@ -64,7 +69,7 @@ public class LocalServerBroadcaster implements AutoCloseable {
     public static final Pattern ADDRESS_PATTERN = Pattern.compile("^\\s*(\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}):(\\d{1,5})\\s*$");
 
     public void start() {
-        Thread forwardPortThread = new Thread(threadGroup, this::forwardPort, "ForwardPort");
+        Thread forwardPortThread = newThread(this::forwardPort, "ForwardPort");
         forwardPortThread.start();
     }
 
@@ -81,7 +86,7 @@ public class LocalServerBroadcaster implements AutoCloseable {
 
                 serverSocket.bind(null);
 
-                Thread broadcastMOTDThread = new Thread(threadGroup, () -> broadcastMOTD(serverSocket.getLocalPort()), "BroadcastMOTD");
+                Thread broadcastMOTDThread = newThread(() -> broadcastMOTD(serverSocket.getLocalPort()), "BroadcastMOTD");
                 broadcastMOTDThread.start();
 
                 LOG.log(Level.INFO, "Listening " + serverSocket.getLocalSocketAddress());
@@ -89,8 +94,8 @@ public class LocalServerBroadcaster implements AutoCloseable {
                 while (running) {
                     Socket forwardedSocket = serverSocket.accept();
                     LOG.log(Level.INFO, "Accepting client");
-                    new Thread(threadGroup, () -> forwardTraffic(forwardingSocket, forwardedSocket), "Forward S->D").start();
-                    new Thread(threadGroup, () -> forwardTraffic(forwardedSocket, forwardingSocket), "Forward D->S").start();
+                    newThread(() -> forwardTraffic(forwardingSocket, forwardedSocket), "Forward S->D").start();
+                    newThread(() -> forwardTraffic(forwardedSocket, forwardingSocket), "Forward D->S").start();
                 }
             }
         } catch (IOException | UnresolvedAddressException e) {
diff --git a/HMCLCore/src/main/java/org/jackhuang/hmcl/util/javafx/BindingMapping.java b/HMCLCore/src/main/java/org/jackhuang/hmcl/util/javafx/BindingMapping.java
index 98d7508e6..897c86270 100644
--- a/HMCLCore/src/main/java/org/jackhuang/hmcl/util/javafx/BindingMapping.java
+++ b/HMCLCore/src/main/java/org/jackhuang/hmcl/util/javafx/BindingMapping.java
@@ -47,22 +47,22 @@ public abstract class BindingMapping<T, U> extends ObjectBinding<U> {
         return of(Bindings.createObjectBinding(() -> mapper.apply(watched), watched));
     }
 
-    protected final ObservableValue<T> predecessor;
+    protected final ObservableValue<? extends T> predecessor;
 
-    public BindingMapping(ObservableValue<T> predecessor) {
+    public BindingMapping(ObservableValue<? extends T> predecessor) {
         this.predecessor = requireNonNull(predecessor);
         bind(predecessor);
     }
 
-    public <V> BindingMapping<?, V> map(Function<U, V> mapper) {
+    public <V> BindingMapping<?, V> map(Function<? super U, ? extends V> mapper) {
         return new MappedBinding<>(this, mapper);
     }
 
-    public <V> BindingMapping<?, V> flatMap(Function<U, ? extends ObservableValue<V>> mapper) {
+    public <V> BindingMapping<?, V> flatMap(Function<? super U, ? extends ObservableValue<? extends V>> mapper) {
         return flatMap(mapper, null);
     }
 
-    public <V> BindingMapping<?, V> flatMap(Function<U, ? extends ObservableValue<V>> mapper, Supplier<V> nullAlternative) {
+    public <V> BindingMapping<?, V> flatMap(Function<? super U, ? extends ObservableValue<? extends V>> mapper, Supplier<? extends V> nullAlternative) {
         return new FlatMappedBinding<>(map(mapper), nullAlternative);
     }
 
@@ -82,7 +82,7 @@ public abstract class BindingMapping<T, U> extends ObjectBinding<U> {
         }
 
         @Override
-        public <V> BindingMapping<?, V> map(Function<T, V> mapper) {
+        public <V> BindingMapping<?, V> map(Function<? super T, ? extends V> mapper) {
             return new MappedBinding<>(predecessor, mapper);
         }
 
@@ -94,9 +94,9 @@ public abstract class BindingMapping<T, U> extends ObjectBinding<U> {
 
     private static class MappedBinding<T, U> extends BindingMapping<T, U> {
 
-        private final Function<T, U> mapper;
+        private final Function<? super T, ? extends U> mapper;
 
-        public MappedBinding(ObservableValue<T> predecessor, Function<T, U> mapper) {
+        public MappedBinding(ObservableValue<? extends T> predecessor, Function<? super T, ? extends U> mapper) {
             super(predecessor);
             this.mapper = mapper;
         }
@@ -107,12 +107,12 @@ public abstract class BindingMapping<T, U> extends ObjectBinding<U> {
         }
     }
 
-    private static class FlatMappedBinding<T extends ObservableValue<U>, U> extends BindingMapping<T, U> {
+    private static class FlatMappedBinding<T extends ObservableValue<? extends U>, U> extends BindingMapping<T, U> {
 
-        private final Supplier<U> nullAlternative;
+        private final Supplier<? extends U> nullAlternative;
         private T lastObservable = null;
 
-        public FlatMappedBinding(ObservableValue<T> predecessor, Supplier<U> nullAlternative) {
+        public FlatMappedBinding(ObservableValue<? extends T> predecessor, Supplier<? extends U> nullAlternative) {
             super(predecessor);
             this.nullAlternative = nullAlternative;
         }
@@ -148,11 +148,11 @@ public abstract class BindingMapping<T, U> extends ObjectBinding<U> {
         private T prev;
         private U value;
 
-        private final Function<T, CompletableFuture<U>> mapper;
+        private final Function<? super T, ? extends CompletableFuture<? extends U>> mapper;
         private T computingPrev;
         private boolean computing = false;
 
-        public AsyncMappedBinding(ObservableValue<T> predecessor, Function<T, CompletableFuture<U>> mapper, U initial) {
+        public AsyncMappedBinding(ObservableValue<? extends T> predecessor, Function<? super T, ? extends CompletableFuture<? extends U>> mapper, U initial) {
             super(predecessor);
             this.value = initial;
             this.mapper = mapper;
@@ -168,7 +168,7 @@ public abstract class BindingMapping<T, U> extends ObjectBinding<U> {
                 computingPrev = currentPrev;
             }
 
-            CompletableFuture<U> task;
+            CompletableFuture<? extends U> task;
             try {
                 task = requireNonNull(mapper.apply(currentPrev));
             } catch (Throwable e) {
diff --git a/HMCLCore/src/main/java/org/jackhuang/hmcl/util/platform/OperatingSystem.java b/HMCLCore/src/main/java/org/jackhuang/hmcl/util/platform/OperatingSystem.java
index 88b4f3976..9038ee26b 100644
--- a/HMCLCore/src/main/java/org/jackhuang/hmcl/util/platform/OperatingSystem.java
+++ b/HMCLCore/src/main/java/org/jackhuang/hmcl/util/platform/OperatingSystem.java
@@ -256,6 +256,7 @@ public enum OperatingSystem {
         return Optional.empty();
     }
 
+    @SuppressWarnings("removal")
     public static void forceGC() {
         System.gc();
         try {