enhance extensibility

Java-Knight/src/main/java/org/project/item/Accessory/Costume.java

@@ -36,13 +36,13 @@ public class Costume extends Accessory implements IDefender {
 
     @Override
     public void AttachTo(Entity entity) {
-        entity.Inventory.remove(this);
+        entity.RemoveFromInventory(this);
         entity.Costume = this;
     }
 
     @Override
     public void DeattachFrom(Entity entity) {
         entity.Costume = null;
-        entity.Inventory.add(this);
+        entity.AddToInventory(this);
     }
 }

Java-Knight/src/main/java/org/project/item/Accessory/Shield.java

@@ -36,13 +36,13 @@ public class Shield extends Accessory implements IDefender {
 
     @Override
     public void AttachTo(Entity entity) {
-        entity.Inventory.remove(this);
+        entity.RemoveFromInventory(this);
         entity.Shield = this;
     }
 
     @Override
     public void DeattachFrom(Entity entity) {
         entity.Shield = null;
-        entity.Inventory.add(this);
+        entity.AddToInventory(this);
     }
 }

Java-Knight/src/main/java/org/project/item/Accessory/Weapon.java

@@ -16,13 +16,13 @@ public class Weapon extends Accessory {
 
     @Override
     public void AttachTo(Entity entity) {
-        entity.Inventory.remove(this);
+        entity.RemoveFromInventory(this);
         entity.Weapon = this;
     }
 
     @Override
     public void DeattachFrom(Entity entity) {
         entity.Weapon = null;
-        entity.Inventory.add(this);
+        entity.AddToInventory(this);
     }
 }