Makes sure manager classes cannot be instantiated or extended

src/main/java/net/knarcraft/permissionsigns/manager/EconomyManager.java

@@ -7,10 +7,14 @@ import org.bukkit.entity.Player;
 /**
  * A manager that performs all Economy tasks
  */
-public class EconomyManager {
+public final class EconomyManager {
 
     private static Economy economy;
 
+    private EconomyManager() {
+
+    }
+
     /**
      * Initializes the economy manager
      *

src/main/java/net/knarcraft/permissionsigns/manager/PermissionManager.java

@@ -20,12 +20,16 @@ import java.util.logging.Level;
 /**
  * A manager that performs all Permission tasks
  */
-public class PermissionManager {
+public final class PermissionManager {
 
     private static Permission permission;
     private static Queue<TemporaryPermission> temporaryPermissions = new PriorityBlockingQueue<>();
     private static final File permissionsFile = new File(PermissionSigns.getInstance().getDataFolder(), "data.yml");
 
+    private PermissionManager() {
+        
+    }
+
     /**
      * Initializes the permission manager
      *

src/main/java/net/knarcraft/permissionsigns/manager/SignManager.java

@@ -25,11 +25,15 @@ import java.util.logging.Level;
 /**
  * A manager for keeping track of known signs
  */
-public class SignManager {
+public final class SignManager {
 
     private static Map<Location, PermissionSign> managedSigns = new HashMap<>();
     private static final File signsFile = new File(PermissionSigns.getInstance().getDataFolder(), "data.yml");
 
+    private SignManager() {
+        
+    }
+
     /**
      * Gets the permission sign at the given location
      *