Improve cache management.

Do not load players in memory, and unload them when they leave.

src/main/java/world/bentobox/challenges/ChallengesManager.java

@@ -133,7 +133,8 @@ public void load()
 
         this.challengeDatabase.loadObjects().forEach(this::loadChallenge);
         this.levelDatabase.loadObjects().forEach(this::loadLevel);
-        this.playersDatabase.loadObjects().forEach(this::loadPlayerData);
+        // It is not necessary to load all players in memory.
+//        this.playersDatabase.loadObjects().forEach(this::loadPlayerData);
     }
 
 
@@ -150,7 +151,8 @@ public void reload()
 
         this.challengeDatabase.loadObjects().forEach(this::loadChallenge);
         this.levelDatabase.loadObjects().forEach(this::loadLevel);
-        this.playersDatabase.loadObjects().forEach(this::loadPlayerData);
+        // It is not necessary to load all players in memory.
+//        this.playersDatabase.loadObjects().forEach(this::loadPlayerData);
     }
 
 
@@ -304,6 +306,28 @@ private void loadPlayerData(ChallengesPlayerData playerData)
     }
 
 
+    /**
+     * This method removes given player from cache data.
+     * @param playerID player ID which cache data must be removed.
+     */
+    public void removeFromCache(UUID playerID)
+    {
+        if (!this.settings.isStoreAsIslandData())
+        {
+            if (this.playerCacheData.containsKey(playerID.toString()))
+            {
+                // save before remove
+                this.savePlayerData(playerID.toString());
+                this.playerCacheData.remove(playerID.toString());
+            }
+        }
+
+        // TODO: It would be necessary to remove also data, if they stores islands.
+        // Unfortunately, I do not know all worlds. Checking everything would be bad. Probably, I could
+        // add extra map that links players with their cached island data?
+    }
+
+
     // ---------------------------------------------------------------------
     // Section: Other storing related methods
     // ---------------------------------------------------------------------
@@ -356,17 +380,17 @@ private void addPlayerData(@NonNull String uniqueID)
         // The player is not in the cache
         // Check if the player exists in the database
 
-        if (this.playersDatabase.objectExists(uniqueID.toString()))
+        if (this.playersDatabase.objectExists(uniqueID))
         {
             // Load player from database
-            ChallengesPlayerData data = this.playersDatabase.loadObject(uniqueID.toString());
+            ChallengesPlayerData data = this.playersDatabase.loadObject(uniqueID);
             // Store in cache
             this.playerCacheData.put(uniqueID, data);
         }
         else
         {
             // Create the player data
-            ChallengesPlayerData pd = new ChallengesPlayerData(uniqueID.toString());
+            ChallengesPlayerData pd = new ChallengesPlayerData(uniqueID);
             this.playersDatabase.saveObject(pd);
             // Add to cache
             this.playerCacheData.put(uniqueID, pd);

src/main/java/world/bentobox/challenges/listeners/SaveListener.java

@@ -4,6 +4,8 @@
 import org.bukkit.event.EventHandler;
 import org.bukkit.event.EventPriority;
 import org.bukkit.event.Listener;
+import org.bukkit.event.player.PlayerKickEvent;
+import org.bukkit.event.player.PlayerQuitEvent;
 import org.bukkit.event.world.WorldSaveEvent;
 
 import world.bentobox.challenges.ChallengesAddon;
@@ -20,16 +22,45 @@ public SaveListener(ChallengesAddon addon) {
     }
 
 
+    /**
+     * This event listener handles world save event.
+     * @param e World Save event.
+     */
     @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
     public void onWorldSave(WorldSaveEvent e)
     {
-        if (!this.addon.getChallengesManager().getAllChallenges(e.getWorld()).isEmpty())
+        // Save only for worlds where exist any challenge addon data.
+        if (this.addon.getChallengesManager().hasAnyChallengeData(e.getWorld()))
         {
             this.addon.getChallengesManager().save();
         }
     }
 
 
+    /**
+     * This event listener handles player kick event.
+     * If player is kicked, then remove it from player cache data.
+     * @param e PlayerKickEvent
+     */
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onPlayerKickEvent(PlayerKickEvent e)
+    {
+        this.addon.getChallengesManager().removeFromCache(e.getPlayer().getUniqueId());
+    }
+
+
+    /**
+     * This event listener handles player quit event.
+     * If player quits server, then remove it from player cache data.
+     * @param e PlayerQuitEvent
+     */
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onPlayerQuitEvent(PlayerQuitEvent e)
+    {
+       this.addon.getChallengesManager().removeFromCache(e.getPlayer().getUniqueId());
+    }
+
+
     // ---------------------------------------------------------------------
     // Section: Variables
     // ---------------------------------------------------------------------