diff --git a/common/src/main/java/com/hibiscusmc/hmccosmetics/api/HMCCosmeticSetupEvent.java b/common/src/main/java/com/hibiscusmc/hmccosmetics/api/HMCCosmeticSetupEvent.java
index 150eadba..54df4c13 100644
--- a/common/src/main/java/com/hibiscusmc/hmccosmetics/api/HMCCosmeticSetupEvent.java
+++ b/common/src/main/java/com/hibiscusmc/hmccosmetics/api/HMCCosmeticSetupEvent.java
@@ -2,6 +2,7 @@ package com.hibiscusmc.hmccosmetics.api;
 
 import org.bukkit.event.Event;
 import org.bukkit.event.HandlerList;
+import org.jetbrains.annotations.NotNull;
 
 public class HMCCosmeticSetupEvent extends Event {
 
@@ -12,6 +13,7 @@ public class HMCCosmeticSetupEvent extends Event {
     private static final HandlerList handlers = new HandlerList();
 
     @Override
+    @NotNull
     public HandlerList getHandlers() {
         return handlers;
     }
diff --git a/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerCosmeticEquipEvent.java b/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerCosmeticEquipEvent.java
index a214a5cb..130a3717 100644
--- a/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerCosmeticEquipEvent.java
+++ b/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerCosmeticEquipEvent.java
@@ -5,10 +5,11 @@ import com.hibiscusmc.hmccosmetics.user.CosmeticUser;
 import org.bukkit.event.Cancellable;
 import org.bukkit.event.Event;
 import org.bukkit.event.HandlerList;
+import org.jetbrains.annotations.NotNull;
 
 public class PlayerCosmeticEquipEvent extends Event implements Cancellable {
 
-    private CosmeticUser user;
+    private final CosmeticUser user;
     private Cosmetic cosmetic;
     private boolean isCancelled;
 
@@ -31,6 +32,7 @@ public class PlayerCosmeticEquipEvent extends Event implements Cancellable {
     private static final HandlerList handlers = new HandlerList();
 
     @Override
+    @NotNull
     public HandlerList getHandlers() {
         return handlers;
     }
@@ -47,7 +49,7 @@ public class PlayerCosmeticEquipEvent extends Event implements Cancellable {
         return cosmetic;
     }
 
-    public void setCosmetic() {
+    public void setCosmetic(Cosmetic cosmetic) {
         this.cosmetic = cosmetic;
     }
 }
diff --git a/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerCosmeticHideEvent.java b/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerCosmeticHideEvent.java
index e617a671..405aff02 100644
--- a/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerCosmeticHideEvent.java
+++ b/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerCosmeticHideEvent.java
@@ -4,11 +4,12 @@ import com.hibiscusmc.hmccosmetics.user.CosmeticUser;
 import org.bukkit.event.Cancellable;
 import org.bukkit.event.Event;
 import org.bukkit.event.HandlerList;
+import org.jetbrains.annotations.NotNull;
 
 public class PlayerCosmeticHideEvent extends Event implements Cancellable {
 
-    private CosmeticUser user;
-    private CosmeticUser.HiddenReason reason;
+    private final CosmeticUser user;
+    private final CosmeticUser.HiddenReason reason;
     private boolean isCancelled;
 
     public PlayerCosmeticHideEvent(CosmeticUser user, CosmeticUser.HiddenReason reason) {
@@ -30,6 +31,7 @@ public class PlayerCosmeticHideEvent extends Event implements Cancellable {
     private static final HandlerList handlers = new HandlerList();
 
     @Override
+    @NotNull
     public HandlerList getHandlers() {
         return handlers;
     }
diff --git a/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerCosmeticRemoveEvent.java b/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerCosmeticRemoveEvent.java
index 639e42ee..ab363363 100644
--- a/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerCosmeticRemoveEvent.java
+++ b/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerCosmeticRemoveEvent.java
@@ -5,11 +5,12 @@ import com.hibiscusmc.hmccosmetics.user.CosmeticUser;
 import org.bukkit.event.Cancellable;
 import org.bukkit.event.Event;
 import org.bukkit.event.HandlerList;
+import org.jetbrains.annotations.NotNull;
 
 public class PlayerCosmeticRemoveEvent extends Event implements Cancellable {
 
-    private CosmeticUser user;
-    private Cosmetic cosmetic;
+    private final CosmeticUser user;
+    private final Cosmetic cosmetic;
     private boolean isCancelled;
 
     public PlayerCosmeticRemoveEvent(CosmeticUser user, Cosmetic cosmetic) {
@@ -31,6 +32,7 @@ public class PlayerCosmeticRemoveEvent extends Event implements Cancellable {
     private static final HandlerList handlers = new HandlerList();
 
     @Override
+    @NotNull
     public HandlerList getHandlers() {
         return handlers;
     }
diff --git a/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerCosmeticShowEvent.java b/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerCosmeticShowEvent.java
index 4fb07db2..6218fcff 100644
--- a/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerCosmeticShowEvent.java
+++ b/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerCosmeticShowEvent.java
@@ -4,10 +4,11 @@ import com.hibiscusmc.hmccosmetics.user.CosmeticUser;
 import org.bukkit.event.Cancellable;
 import org.bukkit.event.Event;
 import org.bukkit.event.HandlerList;
+import org.jetbrains.annotations.NotNull;
 
 public class PlayerCosmeticShowEvent extends Event implements Cancellable {
 
-    private CosmeticUser user;
+    private final CosmeticUser user;
     private boolean isCancelled;
 
     public PlayerCosmeticShowEvent(CosmeticUser user) {
@@ -28,6 +29,7 @@ public class PlayerCosmeticShowEvent extends Event implements Cancellable {
     private static final HandlerList handlers = new HandlerList();
 
     @Override
+    @NotNull
     public HandlerList getHandlers() {
         return handlers;
     }
diff --git a/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerMenuOpenEvent.java b/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerMenuOpenEvent.java
index e8d86a93..b61fe149 100644
--- a/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerMenuOpenEvent.java
+++ b/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerMenuOpenEvent.java
@@ -5,11 +5,12 @@ import com.hibiscusmc.hmccosmetics.user.CosmeticUser;
 import org.bukkit.event.Cancellable;
 import org.bukkit.event.Event;
 import org.bukkit.event.HandlerList;
+import org.jetbrains.annotations.NotNull;
 
 public class PlayerMenuOpenEvent extends Event implements Cancellable {
 
-    private CosmeticUser user;
-    private Menu menu;
+    private final CosmeticUser user;
+    private final Menu menu;
     private boolean isCancelled;
 
     public PlayerMenuOpenEvent(CosmeticUser user, Menu menu) {
@@ -31,6 +32,7 @@ public class PlayerMenuOpenEvent extends Event implements Cancellable {
     private static final HandlerList handlers = new HandlerList();
 
     @Override
+    @NotNull
     public HandlerList getHandlers() {
         return handlers;
     }
diff --git a/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerWardrobeEnterEvent.java b/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerWardrobeEnterEvent.java
index 510a8719..dc19c143 100644
--- a/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerWardrobeEnterEvent.java
+++ b/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerWardrobeEnterEvent.java
@@ -4,10 +4,11 @@ import com.hibiscusmc.hmccosmetics.user.CosmeticUser;
 import org.bukkit.event.Cancellable;
 import org.bukkit.event.Event;
 import org.bukkit.event.HandlerList;
+import org.jetbrains.annotations.NotNull;
 
 public class PlayerWardrobeEnterEvent extends Event implements Cancellable {
 
-    private CosmeticUser user;
+    private final CosmeticUser user;
     private boolean isCancelled;
 
     public PlayerWardrobeEnterEvent(CosmeticUser user) {
@@ -28,6 +29,7 @@ public class PlayerWardrobeEnterEvent extends Event implements Cancellable {
     private static final HandlerList handlers = new HandlerList();
 
     @Override
+    @NotNull
     public HandlerList getHandlers() {
         return handlers;
     }
diff --git a/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerWardrobeLeaveEvent.java b/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerWardrobeLeaveEvent.java
index a867952a..4afb0897 100644
--- a/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerWardrobeLeaveEvent.java
+++ b/common/src/main/java/com/hibiscusmc/hmccosmetics/api/PlayerWardrobeLeaveEvent.java
@@ -4,10 +4,11 @@ import com.hibiscusmc.hmccosmetics.user.CosmeticUser;
 import org.bukkit.event.Cancellable;
 import org.bukkit.event.Event;
 import org.bukkit.event.HandlerList;
+import org.jetbrains.annotations.NotNull;
 
 public class PlayerWardrobeLeaveEvent extends Event implements Cancellable {
 
-    private CosmeticUser user;
+    private final CosmeticUser user;
     private boolean isCancelled;
 
     public PlayerWardrobeLeaveEvent(CosmeticUser user) {
@@ -28,6 +29,7 @@ public class PlayerWardrobeLeaveEvent extends Event implements Cancellable {
     private static final HandlerList handlers = new HandlerList();
 
     @Override
+    @NotNull
     public HandlerList getHandlers() {
         return handlers;
     }