Add some inline packet constructors

src/main/java/net/minestom/server/entity/Player.java

@@ -926,28 +926,15 @@ public class Player extends LivingEntity implements CommandSender, Localizable,
 
     @Override
     public void openBook(@NotNull Book book) {
-        ItemStack writtenBook = ItemStack.builder(Material.WRITTEN_BOOK)
+        final ItemStack writtenBook = ItemStack.builder(Material.WRITTEN_BOOK)
                 .meta(WrittenBookMeta.fromAdventure(book, this))
                 .build();
-
         // Set book in offhand
-        SetSlotPacket setBookPacket = new SetSlotPacket();
+        playerConnection.sendPacket(new SetSlotPacket((byte) 0, 0, (short) PlayerInventoryUtils.OFFHAND_SLOT, writtenBook));
-        setBookPacket.windowId = 0;
-        setBookPacket.slot = PlayerInventoryUtils.OFFHAND_SLOT;
-        setBookPacket.itemStack = writtenBook;
-        playerConnection.sendPacket(setBookPacket);
-
         // Open the book
-        OpenBookPacket openBookPacket = new OpenBookPacket();
+        playerConnection.sendPacket(new OpenBookPacket(Hand.OFF));
-        openBookPacket.hand = Hand.OFF;
-        playerConnection.sendPacket(openBookPacket);
-
         // Restore the item in offhand
-        SetSlotPacket restoreItemPacket = new SetSlotPacket();
+        playerConnection.sendPacket(new SetSlotPacket((byte) 0, 0, (short) PlayerInventoryUtils.OFFHAND_SLOT, getItemInOffHand()));
-        restoreItemPacket.windowId = 0;
-        restoreItemPacket.slot = PlayerInventoryUtils.OFFHAND_SLOT;
-        restoreItemPacket.itemStack = getItemInOffHand();
-        playerConnection.sendPacket(restoreItemPacket);
     }
 
     @Override

src/main/java/net/minestom/server/inventory/Inventory.java

@@ -199,13 +199,9 @@ public class Inventory extends AbstractInventory implements Viewable {
      */
     public void setCursorItem(@NotNull Player player, @NotNull ItemStack cursorItem) {
         final ItemStack currentCursorItem = cursorPlayersItem.getOrDefault(player, ItemStack.AIR);
-        final boolean similar = currentCursorItem.isSimilar(cursorItem);
+        if (!currentCursorItem.isSimilar(cursorItem)) {
-
+            player.getPlayerConnection().sendPacket(SetSlotPacket.createCursorPacket(cursorItem));
-        if (!similar) {
-            final SetSlotPacket setSlotPacket = SetSlotPacket.createCursorPacket(cursorItem);
-            player.getPlayerConnection().sendPacket(setSlotPacket);
         }
-
         if (!cursorItem.isAir()) {
             this.cursorPlayersItem.put(player, cursorItem);
         } else {
@@ -225,11 +221,7 @@ public class Inventory extends AbstractInventory implements Viewable {
     @Override
     protected synchronized void safeItemInsert(int slot, @NotNull ItemStack itemStack) {
         this.itemStacks[slot] = itemStack;
-        SetSlotPacket setSlotPacket = new SetSlotPacket();
+        sendPacketToViewers(new SetSlotPacket(getWindowId(), 0, (short) slot, itemStack));
-        setSlotPacket.windowId = getWindowId();
-        setSlotPacket.slot = (short) slot;
-        setSlotPacket.itemStack = itemStack;
-        sendPacketToViewers(setSlotPacket);
     }
 
     /**
@@ -237,12 +229,8 @@ public class Inventory extends AbstractInventory implements Viewable {
      *
      * @return a new {@link WindowItemsPacket} packet
      */
-    @NotNull
+    private @NotNull WindowItemsPacket createNewWindowItemsPacket() {
-    private WindowItemsPacket createNewWindowItemsPacket() {
+        return new WindowItemsPacket(getWindowId(), 0, getItemStacks(), ItemStack.AIR);
-        WindowItemsPacket windowItemsPacket = new WindowItemsPacket();
-        windowItemsPacket.windowId = getWindowId();
-        windowItemsPacket.items = getItemStacks();
-        return windowItemsPacket;
     }
 
     /**
@@ -253,11 +241,7 @@ public class Inventory extends AbstractInventory implements Viewable {
      * @see <a href="https://wiki.vg/Protocol#Window_Property">https://wiki.vg/Protocol#Window_Property</a>
      */
     protected void sendProperty(@NotNull InventoryProperty property, short value) {
-        WindowPropertyPacket windowPropertyPacket = new WindowPropertyPacket();
+        sendPacketToViewers(new WindowPropertyPacket(getWindowId(), property.getProperty(), value));
-        windowPropertyPacket.windowId = getWindowId();
-        windowPropertyPacket.property = property.getProperty();
-        windowPropertyPacket.value = value;
-        sendPacketToViewers(windowPropertyPacket);
     }
 
     /**
@@ -352,7 +336,7 @@ public class Inventory extends AbstractInventory implements Viewable {
             playerInventory.setItemStack(clickSlot, clickResult.getClicked());
         }
 
-        if(clickResult.doRefresh()){
+        if (clickResult.doRefresh()) {
             update(player);
         }
 

src/main/java/net/minestom/server/inventory/PlayerInventory.java

@@ -239,11 +239,7 @@ public class PlayerInventory extends AbstractInventory implements EquipmentHandl
      * @param itemStack the item stack in the slot
      */
     protected void sendSlotRefresh(short slot, ItemStack itemStack) {
-        SetSlotPacket setSlotPacket = new SetSlotPacket();
+        player.getPlayerConnection().sendPacket(new SetSlotPacket((byte) 0, 0, slot, itemStack));
-        setSlotPacket.windowId = 0;
-        setSlotPacket.slot = slot;
-        setSlotPacket.itemStack = itemStack;
-        player.getPlayerConnection().sendPacket(setSlotPacket);
     }
 
     /**
@@ -253,16 +249,11 @@ public class PlayerInventory extends AbstractInventory implements EquipmentHandl
      */
     private WindowItemsPacket createWindowItemsPacket() {
         ItemStack[] convertedSlots = new ItemStack[INVENTORY_SIZE];
-
         for (int i = 0; i < itemStacks.length; i++) {
             final int slot = convertToPacketSlot(i);
             convertedSlots[slot] = itemStacks[i];
         }
-
+        return new WindowItemsPacket((byte) 0, 0, convertedSlots, ItemStack.AIR);
-        WindowItemsPacket windowItemsPacket = new WindowItemsPacket();
-        windowItemsPacket.windowId = 0;
-        windowItemsPacket.items = convertedSlots;
-        return windowItemsPacket;
     }
 
     @Override

src/main/java/net/minestom/server/network/packet/server/play/OpenBookPacket.java

@@ -9,9 +9,15 @@ import org.jetbrains.annotations.NotNull;
 
 public class OpenBookPacket implements ServerPacket {
 
-    public Player.Hand hand = Player.Hand.MAIN;
+    public Player.Hand hand;
 
-    public OpenBookPacket() {}
+    public OpenBookPacket(Player.Hand hand) {
+        this.hand = hand;
+    }
+
+    public OpenBookPacket() {
+        this(Player.Hand.MAIN);
+    }
 
     @Override
     public void write(@NotNull BinaryWriter writer) {

src/main/java/net/minestom/server/network/packet/server/play/SetSlotPacket.java

@@ -14,8 +14,15 @@ public class SetSlotPacket implements ServerPacket {
     public short slot;
     public ItemStack itemStack;
 
+    public SetSlotPacket(byte windowId, int stateId, short slot, ItemStack itemStack) {
+        this.windowId = windowId;
+        this.stateId = stateId;
+        this.slot = slot;
+        this.itemStack = itemStack;
+    }
+
     public SetSlotPacket() {
-        itemStack = ItemStack.AIR;
+        this((byte) 0, 0, (short) 0, ItemStack.AIR);
     }
 
     @Override
@@ -45,12 +52,7 @@ public class SetSlotPacket implements ServerPacket {
      * @param cursorItem the cursor item
      * @return a set slot packet to change a player cursor item
      */
-    @NotNull
+    public static @NotNull SetSlotPacket createCursorPacket(@NotNull ItemStack cursorItem) {
-    public static SetSlotPacket createCursorPacket(@NotNull ItemStack cursorItem) {
+        return new SetSlotPacket((byte) -1, -1, (short) 0, cursorItem);
-        SetSlotPacket setSlotPacket = new SetSlotPacket();
-        setSlotPacket.windowId = -1;
-        setSlotPacket.slot = -1;
-        setSlotPacket.itemStack = cursorItem;
-        return setSlotPacket;
     }
 }

src/main/java/net/minestom/server/network/packet/server/play/WindowItemsPacket.java

@@ -12,12 +12,17 @@ public class WindowItemsPacket implements ServerPacket {
     public byte windowId;
     public int stateId;
     public ItemStack[] items;
-    public ItemStack carriedItem = ItemStack.AIR;
+    public ItemStack carriedItem;
+
+    public WindowItemsPacket(byte windowId, int stateId, ItemStack[] items, ItemStack carriedItem) {
+        this.windowId = windowId;
+        this.stateId = stateId;
+        this.items = items;
+        this.carriedItem = carriedItem;
+    }
 
-    /**
-     * Default constructor, required for reflection operations.
-     */
     public WindowItemsPacket() {
+        this((byte) 0, 0, new ItemStack[]{}, ItemStack.AIR);
     }
 
     @Override

src/main/java/net/minestom/server/network/packet/server/play/WindowPropertyPacket.java

@@ -12,10 +12,15 @@ public class WindowPropertyPacket implements ServerPacket {
     public short property;
     public short value;
 
-    /**
+    public WindowPropertyPacket(byte windowId, short property, short value) {
-     * Default constructor, required for reflection operations.
+        this.windowId = windowId;
-     */
+        this.property = property;
-    public WindowPropertyPacket() {}
+        this.value = value;
+    }
+
+    public WindowPropertyPacket() {
+        this((byte) 0, (short) 0, (short) 0);
+    }
 
     @Override
     public void write(@NotNull BinaryWriter writer) {