Wrap CheckpointUtils for OpenJDK support, remove Border debug messages

FightSystem/FightSystem_Core/src/de/steamwar/fightsystem/listener/Border.java

@@ -64,7 +64,6 @@ public class Border {
 
         ghostBarriers.put(player.getUniqueId(), new HashSet<>());
         lastLocation.put(player.getUniqueId(), player.getLocation());
-        FightSystem.getPlugin().getLogger().log(Level.INFO, () -> player.getName() + " was added to border " + name);
     }
 
     public boolean contains(Player player) {
@@ -72,7 +71,6 @@ public class Border {
     }
 
     public void removePlayer(Player player) {
-        FightSystem.getPlugin().getLogger().log(Level.INFO, () -> player.getName() + " was removed from border " + name);
         lastLocation.remove(player.getUniqueId());
         Set<Block> blocks = ghostBarriers.remove(player.getUniqueId());
         if(blocks == null || !player.isOnline())

SpigotCore/SpigotCore_Main/src/de/steamwar/core/CheckpointUtils.java

@@ -45,10 +45,27 @@ public class CheckpointUtils {
     private CheckpointUtils() {}
 
     public static void signalHandler() {
-        Signal.handle(new Signal("USR1"), signal -> Bukkit.getScheduler().runTask(Core.getInstance(), CheckpointUtils::freeze));
+        try {
+            J9Wrapper.signalHandler();
+        } catch (NoClassDefFoundError e) {
+            //ignore
+        }
     }
 
     public static void freeze() {
+        try {
+            J9Wrapper.freeze();
+        } catch (NoClassDefFoundError e) {
+            //ignore
+        }
+    }
+
+    private static class J9Wrapper {
+        private static void signalHandler() {
+            Signal.handle(new Signal("USR1"), signal -> Bukkit.getScheduler().runTask(Core.getInstance(), CheckpointUtils::freeze));
+        }
+
+        private static void freeze() {
             String checkpointFile = System.getProperty("checkpoint");
             if(!CRIUSupport.isCheckpointAllowed() || checkpointFile == null) {
                 Bukkit.shutdown();
@@ -90,6 +107,7 @@ public class CheckpointUtils {
             }
         }
 
+
         private static final Reflection.FieldAccessor<List> channelFutures = Reflection.getField(TinyProtocol.serverConnection, List.class, 0, ChannelFuture.class);
         private static final Reflection.MethodInvoker bind = Reflection.getMethod(TinyProtocol.serverConnection, null, InetAddress.class, int.class);
         private static void freezeInternal(Path path) throws Exception {
@@ -145,3 +163,4 @@ public class CheckpointUtils {
             Core.getInstance().getLogger().log(Level.INFO, "Checkpoint restored");
         }
     }
+}