Implement data removing after island deletion.

src/main/java/world/bentobox/visit/listeners/IslandEventsListener.java

@@ -0,0 +1,48 @@
+//
+// Created by BONNe
+// Copyright - 2020
+//
+
+
+package world.bentobox.visit.listeners;
+
+
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
+import org.bukkit.event.Listener;
+
+import world.bentobox.bentobox.api.events.island.IslandDeleteEvent;
+import world.bentobox.visit.VisitAddon;
+
+
+/**
+ * This listener deletes island data after it is removed.
+ */
+public class IslandEventsListener implements Listener
+{
+    /**
+     * @param addon - addon
+     */
+    public IslandEventsListener(VisitAddon addon)
+    {
+        this.addon = addon;
+    }
+
+
+    /**
+     * This method handles island deletion. On island deletion it should remove generator data too.
+     *
+     * @param event IslandDeletedEvent instance.
+     */
+    @EventHandler(priority = EventPriority.MONITOR, ignoreCancelled = true)
+    public void onIslandDelete(IslandDeleteEvent event)
+    {
+        this.addon.getAddonManager().removeData(event.getIsland());
+    }
+
+
+    /**
+     * stores addon instance
+     */
+    private final VisitAddon addon;
+}

src/main/java/world/bentobox/visit/managers/VisitAddonManager.java

@@ -4,7 +4,7 @@
 import org.bukkit.Bukkit;
 import org.bukkit.Location;
 import org.bukkit.World;
-import org.eclipse.jdt.annotation.NonNull;
+import org.jetbrains.annotations.NotNull;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
@@ -65,7 +65,7 @@ public void load()
      *
      * @param islandSettings object that must be loaded in local cache
      */
-    private void loadSettings(@NonNull IslandVisitSettings islandSettings)
+    private void loadSettings(@NotNull IslandVisitSettings islandSettings)
     {
         this.loadSettings(islandSettings, true, null, true);
     }
@@ -81,23 +81,11 @@ private void loadSettings(@NonNull IslandVisitSettings islandSettings)
      * @param silent of type boolean that indicate if message to user must be sent.
      * @return boolean that indicate about load status.
      */
-    public boolean loadSettings(@NonNull IslandVisitSettings islandSettings,
+    public boolean loadSettings(@NotNull IslandVisitSettings islandSettings,
         boolean overwrite,
         User user,
         boolean silent)
     {
-        // This may happen if database somehow failed to load challenge and return
-        // null as input.
-        if (islandSettings == null)
-        {
-            if (!silent)
-            {
-                user.sendMessage("load-error", "[value]", "NULL");
-            }
-
-            return false;
-        }
-
         if (this.visitSettingsCacheData.containsKey(islandSettings.getUniqueId()))
         {
             if (!overwrite)
@@ -176,6 +164,17 @@ public void wipeDatabase()
     }
 
 
+    /**
+     * This method removes data from database for given island.
+     * @param island Island which data must be removed.
+     */
+    public void removeData(@NotNull Island island)
+    {
+        this.visitSettingsCacheData.remove(island.getUniqueId());
+        this.visitSettingsDatabase.deleteID(island.getUniqueId());
+    }
+
+
     /**
      * This method returns island visit settings object from cache for given island.
      *