Add some NotNull annotations

Author: NichtStudioCode

invui-core/src/main/java/xyz/xenondevs/invui/item/ItemProvider.java

@@ -2,31 +2,32 @@
 
 import org.bukkit.Material;
 import org.bukkit.inventory.ItemStack;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.util.function.Supplier;
 
-public interface ItemProvider extends Supplier<ItemStack>, Cloneable {
+public interface ItemProvider extends Supplier<@NotNull ItemStack>, Cloneable {
 
     /**
      * An {@link ItemProvider} for an {@link ItemStack}.
      */
-    ItemProvider EMPTY = new ItemWrapper(new ItemStack(Material.AIR));
+    @NotNull ItemProvider EMPTY = new ItemWrapper(new ItemStack(Material.AIR));
 
     /**
      * Gets the {@link ItemStack} translated in the specified language.
      *
      * @param lang The language to translate the item in.
      * @return The {@link ItemStack}
      */
-    ItemStack get(@Nullable String lang);
+    @NotNull ItemStack get(@Nullable String lang);
 
     /**
      * Gets the {@link ItemStack} without requesting a specific language.
      *
      * @return The {@link ItemStack}
      */
-    default ItemStack get() {
+    default @NotNull ItemStack get() {
         return get(null);
     }
 

invui-core/src/main/java/xyz/xenondevs/invui/item/ItemWrapper.java

@@ -1,6 +1,7 @@
 package xyz.xenondevs.invui.item;
 
 import org.bukkit.inventory.ItemStack;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.UUID;
 
@@ -17,7 +18,7 @@ public ItemWrapper(ItemStack itemStack) {
     }
 
     @Override
-    public ItemStack get(String lang) {
+    public @NotNull ItemStack get(String lang) {
         return itemStack;
     }