Use CloneUtils for deep copy

src/main/java/net/minestom/server/item/metadata/CompassMeta.java

@@ -1,6 +1,7 @@
 package net.minestom.server.item.metadata;
 
 import net.minestom.server.utils.Position;
+import net.minestom.server.utils.clone.CloneUtils;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
@@ -95,7 +96,7 @@ public class CompassMeta extends ItemMeta {
         CompassMeta compassMeta = (CompassMeta) super.clone();
         compassMeta.lodestoneTracked = lodestoneTracked;
         compassMeta.lodestoneDimension = lodestoneDimension;
-        compassMeta.lodestonePosition = lodestonePosition != null ? lodestonePosition.clone() : null;
+        compassMeta.lodestonePosition = CloneUtils.optionalClone(lodestonePosition);
 
         return compassMeta;
     }

src/main/java/net/minestom/server/item/metadata/CrossbowMeta.java

@@ -4,6 +4,7 @@ import net.minestom.server.item.ItemStack;
 import net.minestom.server.item.Material;
 import net.minestom.server.registry.Registries;
 import net.minestom.server.utils.NBTUtils;
+import net.minestom.server.utils.clone.CloneUtils;
 import net.minestom.server.utils.validate.Check;
 import org.jetbrains.annotations.NotNull;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
@@ -183,9 +184,9 @@ public class CrossbowMeta extends ItemMeta {
     public ItemMeta clone() {
         CrossbowMeta crossbowMeta = (CrossbowMeta) super.clone();
         crossbowMeta.triple = triple;
-        crossbowMeta.projectile1 = projectile1 == null ? null : projectile1.clone();
+        crossbowMeta.projectile1 = CloneUtils.optionalClone(projectile1);
-        crossbowMeta.projectile2 = projectile2 == null ? null : projectile2.clone();
+        crossbowMeta.projectile2 = CloneUtils.optionalClone(projectile2);
-        crossbowMeta.projectile3 = projectile3 == null ? null : projectile3.clone();
+        crossbowMeta.projectile3 = CloneUtils.optionalClone(projectile3);
 
         crossbowMeta.charged = charged;
 

src/main/java/net/minestom/server/item/metadata/MapMeta.java

@@ -1,19 +1,21 @@
 package net.minestom.server.item.metadata;
 
 import net.minestom.server.chat.ChatColor;
+import net.minestom.server.utils.clone.CloneUtils;
+import net.minestom.server.utils.clone.PublicCloneable;
 import org.jetbrains.annotations.NotNull;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 import org.jglrxavpok.hephaistos.nbt.NBTList;
 import org.jglrxavpok.hephaistos.nbt.NBTTypes;
 
-import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
 
 public class MapMeta extends ItemMeta {
 
     private int mapId;
     private int mapScaleDirection = 1;
-    private List<MapDecoration> decorations = new ArrayList<>();
+    private List<MapDecoration> decorations = new CopyOnWriteArrayList<>();
     private ChatColor mapColor = ChatColor.NO_COLOR;
 
     public MapMeta() {
@@ -198,18 +200,18 @@ public class MapMeta extends ItemMeta {
         MapMeta mapMeta = (MapMeta) super.clone();
         mapMeta.setMapId(mapId);
         mapMeta.setMapScaleDirection(mapScaleDirection);
-        mapMeta.decorations.addAll(decorations);
+        mapMeta.decorations = CloneUtils.cloneCopyOnWriteArrayList(decorations);
         mapMeta.setMapColor(mapColor);
         return mapMeta;
     }
 
-    public static class MapDecoration {
+    public static class MapDecoration implements PublicCloneable<MapDecoration> {
         private final String id;
         private final byte type;
         private final byte x, z;
         private final double rotation;
 
-        public MapDecoration(String id, byte type, byte x, byte z, double rotation) {
+        public MapDecoration(@NotNull String id, byte type, byte x, byte z, double rotation) {
             this.id = id;
             this.type = type;
             this.x = x;
@@ -262,6 +264,17 @@ public class MapMeta extends ItemMeta {
         public double getRotation() {
             return rotation;
         }
+
+        @NotNull
+        @Override
+        public MapDecoration clone() {
+            try {
+                return (MapDecoration) super.clone();
+            } catch (CloneNotSupportedException e) {
+                e.printStackTrace();
+                throw new IllegalStateException("Something weird happened");
+            }
+        }
     }
 
 }

src/main/java/net/minestom/server/item/metadata/WritableBookMeta.java

@@ -69,9 +69,6 @@ public class WritableBookMeta extends ItemMeta {
     @NotNull
     @Override
     public ItemMeta clone() {
-        WritableBookMeta writableBookMeta = (WritableBookMeta) super.clone();
+        return super.clone();
-        writableBookMeta.pages.addAll(pages);
-
-        return writableBookMeta;
     }
 }

src/main/java/net/minestom/server/utils/clone/CloneUtils.java

@@ -1,12 +1,18 @@
 package net.minestom.server.utils.clone;
 
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
 
 public final class CloneUtils {
 
+    @Nullable
+    public static <T extends PublicCloneable> T optionalClone(@Nullable T object) {
+        return object != null ? (T) object.clone() : null;
+    }
+
     @NotNull
     public static <T extends PublicCloneable> CopyOnWriteArrayList cloneCopyOnWriteArrayList(@NotNull List<T> list) {
         CopyOnWriteArrayList<T> result = new CopyOnWriteArrayList<>();