refactoring and code cleanup

src/main/java/me/unurled/sacredrealms/sr/components/attributes/Attribute.java

@@ -50,6 +50,7 @@ public enum Attribute {
     return minValue;
   }
 
+  @SuppressWarnings("SameReturnValue")
   public PersistentDataType<Double, Double> getType() {
     return PersistentDataType.DOUBLE;
   }

src/main/java/me/unurled/sacredrealms/sr/components/combat/CombatManager.java

@@ -17,11 +17,13 @@ import org.bukkit.event.entity.EntityDamageByBlockEvent;
 import org.bukkit.event.entity.EntityDamageByEntityEvent;
 import org.bukkit.event.entity.EntityDamageEvent;
 import org.bukkit.inventory.EntityEquipment;
+import org.jetbrains.annotations.NotNull;
 
+@SuppressWarnings("EmptyMethod")
 public class CombatManager extends Manager {
 
   @EventHandler
-  public void onDamage(EntityDamageByBlockEvent e) {
+  public void onDamage(@NotNull EntityDamageByBlockEvent e) {
     // TODO: Implement
     // blast enchant :shrug:
     // fall damage, fire damage, etc
@@ -31,7 +33,7 @@ public class CombatManager extends Manager {
 
   // TODO: Finish this
   @EventHandler
-  public void onDamage(EntityDamageByEntityEvent e) {
+  public void onDamage(@NotNull EntityDamageByEntityEvent e) {
     e.setDamage(0.0);
 
     if (!(e.getDamager() instanceof LivingEntity damager)

src/main/java/me/unurled/sacredrealms/sr/components/entity/EntityManager.java

@@ -38,7 +38,7 @@ public class EntityManager extends Manager {
   }
 
   @EventHandler
-  public void onEntitySpawn(EntitySpawnEvent e) {
+  public void onEntitySpawn(@NotNull EntitySpawnEvent e) {
     if (e.getEntity() instanceof Player) return;
 
     if (isSREntity(e.getEntity().getUniqueId())) return;

src/main/java/me/unurled/sacredrealms/sr/components/item/ItemManager.java

@@ -4,6 +4,7 @@ import java.util.HashMap;
 import me.unurled.sacredrealms.sr.managers.Manager;
 import org.bukkit.NamespacedKey;
 
+@SuppressWarnings("EmptyMethod")
 public class ItemManager extends Manager {
   public static final NamespacedKey ID = new NamespacedKey("sr", "id");
 

src/main/java/me/unurled/sacredrealms/sr/components/item/abilities/Ability.java

@@ -1,6 +1,7 @@
 package me.unurled.sacredrealms.sr.components.item.abilities;
 
 /** Represents an ability that an item can have. TODO: Implement this class */
+@SuppressWarnings("unused")
 public class Ability {
 
   private final String name;

src/main/java/me/unurled/sacredrealms/sr/components/player/PlayerManager.java

@@ -40,11 +40,19 @@ public class PlayerManager extends Manager {
       return;
     }
     DataHandler dh = dm.getDataHandler();
-  }
+    // save all players
+    Gson gson =
+        new GsonBuilder()
+            .excludeFieldsWithoutExposeAnnotation()
+            .registerTypeAdapter(Inventory.class, new InventorySerializer())
+            .registerTypeAdapter(PotionEffect.class, new PotionEffectSerializer())
+            .create();
+    for (SRPlayer player : players.values()) {
+      dh.set(PLAYER_KEY + player.getUuid(), gson.toJson(player));
+    }
 
-  /** Load the data */
-  /*@Override
-  public void loadData() {}*/
+    players.clear();
+  }
 
   @Nullable
   public SRPlayer getPlayer(UUID uuid) {
@@ -89,7 +97,7 @@ public class PlayerManager extends Manager {
   }
 
   @EventHandler
-  public void onPlayerQuit(PlayerQuitEvent e) {
+  public void onPlayerQuit(@NotNull PlayerQuitEvent e) {
     SRPlayer player = getPlayer(e.getPlayer().getUniqueId());
     if (player == null) {
       return;