General cleanup

common/src/main/java/me/lucko/luckperms/data/methods/FlatfileDatastore.java

@@ -319,9 +319,9 @@ public class FlatfileDatastore extends Datastore {
 
     @Override
     public boolean loadAllGroups() {
-        List<String> groups = Arrays.asList(groupsDir.list((dir, name1) -> name1.endsWith(".json")))
-                .stream().map(s -> s.substring(0, s.length() - 5))
-                .collect(Collectors.toList());
+        String[] fileNames = groupsDir.list((dir, name) -> name.endsWith(".json"));
+        if (fileNames == null) return false;
+        List<String> groups = Arrays.stream(fileNames).map(s -> s.substring(0, s.length() - 5)).collect(Collectors.toList());
 
         plugin.getGroupManager().unloadAll();
         groups.forEach(this::loadGroup);

common/src/main/java/me/lucko/luckperms/data/methods/MySQLDatastore.java

@@ -50,7 +50,7 @@ public class MySQLDatastore extends SQLDatastore {
     @Override
     public void shutdown() {
         if (hikari != null) {
-            hikari.shutdown();
+            hikari.close();
         }
     }
 

common/src/main/java/me/lucko/luckperms/data/methods/SQLDatastore.java

@@ -19,7 +19,6 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 import java.util.UUID;
-import java.util.logging.Level;
 
 @SuppressWarnings("UnnecessaryLocalVariable")
 abstract class SQLDatastore extends Datastore {