NMS 1.19.3 SPIGOT, Change ItemStack Size

ItemUtil.java

class ChangeMaxStackSize {

    private net.minecraft.world.item.ItemStack stack;
    private Item nmsItem;
    private ItemStack item;

    public ChangeMaxStackSize(ItemStack itemStack, int maxStackSize) throws NoSuchFieldException, IllegalAccessException {
        this.item = itemStack;
        this.stack = CraftItemStack.asNMSCopy(itemStack);
        this.nmsItem = stack.o().c();

        setMaxStackSize(maxStackSize);
    }

    private void setMaxStackSize(int size) throws NoSuchFieldException, IllegalAccessException {
        Field field = this.nmsItem.getClass().getSuperclass().getDeclaredField("d");
        field.setAccessible(true);
        field.setInt(this.nmsItem, size);
    }

    public Item getNmsItem() {
        return nmsItem;
    }

    public net.minecraft.world.item.ItemStack getStack() {
        return stack;
    }

    public ItemStack getItem() {
        return item;
    }

    public ItemStack itemStack() {
        return CraftItemStack.asBukkitCopy(this.stack);
    }
}