From f52d9903d50931995f9aa2827bad1194d26a8529 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hakan=20Karg=C4=B1n?= <hakankargin_2003@hotmail.com>
Date: Fri, 18 Mar 2022 23:05:17 +0300
Subject: [PATCH] - Finished javadocs, annotations and null checkers in
 project. - Optimized imports.

---
 api/src/main/java/com/hakan/core/HCore.java   | 463 ++++++++++++++++--
 .../hakan/core/hologram/HHologramHandler.java |   2 +
 .../hakan/core/ui/inventory/HInventory.java   |  88 +++-
 .../core/ui/inventory/HInventoryHandler.java  |  81 ++-
 .../inventory/builder/HInventoryBuilder.java  |  89 +++-
 .../core/ui/inventory/item/ClickableItem.java |  21 +
 .../listeners/bukkit/PlayerQuitListener.java  |  17 +-
 .../bukkit/PluginDisableListener.java         |  17 +-
 .../inventory/InventoryClickListener.java     |  16 +-
 .../inventory/InventoryCloseListener.java     |  18 +-
 .../core/ui/inventory/pagination/Page.java    |  22 +-
 .../ui/inventory/pagination/Pagination.java   | 138 +++++-
 .../message/bossbar/HBossBar_v1_8_R3.java     |   1 -
 13 files changed, 867 insertions(+), 106 deletions(-)

diff --git a/api/src/main/java/com/hakan/core/HCore.java b/api/src/main/java/com/hakan/core/HCore.java
index d1396339..19d6b6b8 100644
--- a/api/src/main/java/com/hakan/core/HCore.java
+++ b/api/src/main/java/com/hakan/core/HCore.java
@@ -1,7 +1,7 @@
 package com.hakan.core;
 
-import com.hakan.core.command.functional.HCommand;
 import com.hakan.core.command.HCommandExecutor;
+import com.hakan.core.command.functional.HCommand;
 import com.hakan.core.hologram.HHologram;
 import com.hakan.core.hologram.HHologramHandler;
 import com.hakan.core.hooks.Metrics;
@@ -23,7 +23,6 @@
 import com.hakan.core.worldborder.HWorldBorderHandler;
 import com.hakan.core.worldborder.border.HBorderColor;
 import com.hakan.core.worldborder.border.HWorldBorder;
-import org.apache.commons.lang.Validate;
 import org.bukkit.Bukkit;
 import org.bukkit.Location;
 import org.bukkit.Material;
@@ -45,6 +44,7 @@ public class HCore {
 
     private static JavaPlugin instance;
 
+    @Nonnull
     public static JavaPlugin getInstance() {
         return HCore.instance;
     }
@@ -72,6 +72,13 @@ public static void initialize(@Nonnull JavaPlugin plugin) {
     /*
     OTHERS
      */
+
+    /**
+     * Gets version string (example: v1_8_R3)
+     *
+     * @return Version string
+     */
+    @Nonnull
     public static String getVersionString() {
         return Bukkit.getServer().getClass().getName().split("\\.")[3];
     }
@@ -80,14 +87,34 @@ public static String getVersionString() {
     /*
     SCHEDULER
      */
+
+    /**
+     * Creates scheduler.
+     *
+     * @param async Async status.
+     * @return HScheduler.
+     */
+    @Nonnull
     public static HScheduler scheduler(boolean async) {
         return new HScheduler(HCore.instance, async);
     }
 
+    /**
+     * Creates async scheduler.
+     *
+     * @return HScheduler.
+     */
+    @Nonnull
     public static HScheduler asyncScheduler() {
         return new HScheduler(HCore.instance, true);
     }
 
+    /**
+     * Creates sync scheduler.
+     *
+     * @return HScheduler.
+     */
+    @Nonnull
     public static HScheduler syncScheduler() {
         return new HScheduler(HCore.instance, false);
     }
@@ -96,82 +123,210 @@ public static HScheduler syncScheduler() {
     /*
     INVENTORY API
      */
+
+    /**
+     * Gets content as safe.
+     *
+     * @return Content.
+     */
+    @Nonnull
     public static Map<UUID, HInventory> getInventoryContentSafe() {
         return HInventoryHandler.getContentSafe();
     }
 
+    /**
+     * Gets content.
+     *
+     * @return Content.
+     */
+    @Nonnull
     public static Map<UUID, HInventory> getInventoryContent() {
         return HInventoryHandler.getContent();
     }
 
+    /**
+     * Gets values as safe.
+     *
+     * @return Values.
+     */
+    @Nonnull
     public static Collection<HInventory> getInventoryValuesSafe() {
         return HInventoryHandler.getValuesSafe();
     }
 
+    /**
+     * Gets values.
+     *
+     * @return Values.
+     */
+    @Nonnull
     public static Collection<HInventory> getInventoryValues() {
         return HInventoryHandler.getValues();
     }
 
-    public static Optional<HInventory> findInventoryByPlayer(Player player) {
+    /**
+     * Finds HInventory by player.
+     *
+     * @param player Player.
+     * @return HInventory as optional.
+     */
+    @Nonnull
+    public static Optional<HInventory> findInventoryByPlayer(@Nonnull Player player) {
         return HInventoryHandler.findByPlayer(player);
     }
 
-    public static HInventory getInventoryByPlayer(Player player) {
+    /**
+     * Gets HInventory by player.
+     *
+     * @param player Player.
+     * @return HInventory.
+     */
+    @Nonnull
+    public static HInventory getInventoryByPlayer(@Nonnull Player player) {
         return HInventoryHandler.getByPlayer(player);
     }
 
-    public static Optional<HInventory> findInventoryByUID(UUID uid) {
+    /**
+     * Finds HInventory by UID.
+     *
+     * @param uid Player UID.
+     * @return HInventory as optional.
+     */
+    @Nonnull
+    public static Optional<HInventory> findInventoryByUID(@Nonnull UUID uid) {
         return HInventoryHandler.findByUID(uid);
     }
 
-    public static HInventory getInventoryByUID(UUID uid) {
+    /**
+     * Gets HInventory by UID.
+     *
+     * @param uid Player UId.
+     * @return HInventory.
+     */
+    @Nonnull
+    public static HInventory getInventoryByUID(@Nonnull UUID uid) {
         return HInventoryHandler.getByUID(uid);
     }
 
-    public static HInventoryBuilder buildInventory(String id) {
-        return new HInventoryBuilder(id);
+    /**
+     * Creates builder with ID.
+     *
+     * @param id ID.
+     * @return HInventoryBuilder.
+     */
+    @Nonnull
+    public static HInventoryBuilder buildInventory(@Nonnull String id) {
+        return HInventoryHandler.builder(id);
     }
 
-    public static HInventory createInventory(String id, String title, InventoryType type, int size) {
-        return new HInventoryBuilder(id).title(title).type(type).size(size).build();
+    /**
+     * Creates HInventory with ID.
+     *
+     * @param id ID.
+     * @return HInventory.
+     */
+    @Nonnull
+    public static HInventory createInventory(@Nonnull String id, @Nonnull String title, @Nonnull InventoryType type, int size) {
+        return HInventoryHandler.builder(id).title(title).type(type).size(size).build();
     }
 
 
     /*
     SIGN
      */
+
+    /**
+     * Gets content as safe.
+     *
+     * @return Content.
+     */
+    @Nonnull
     public static Map<UUID, HSign> getSignContentSafe() {
         return HSignHandler.getContentSafe();
     }
 
+    /**
+     * Gets content.
+     *
+     * @return Content
+     */
+    @Nonnull
     public static Map<UUID, HSign> getSignContent() {
         return HSignHandler.getContent();
     }
 
+    /**
+     * Gets values as safe.
+     *
+     * @return Values.
+     */
+    @Nonnull
     public static Collection<HSign> getSignValuesSafe() {
         return HSignHandler.getValuesSafe();
     }
 
+    /**
+     * Gets values.
+     *
+     * @return Values.
+     */
+    @Nonnull
     public static Collection<HSign> getSignValues() {
         return HSignHandler.getValues();
     }
 
-    public static Optional<HSign> findSignByPlayer(Player player) {
+    /**
+     * Finds HSign by player.
+     *
+     * @param player Player.
+     * @return HSign as optional.
+     */
+    @Nonnull
+    public static Optional<HSign> findSignByPlayer(@Nonnull Player player) {
         return HSignHandler.findByPlayer(player);
     }
 
-    public static HSign getSignByPlayer(Player player) {
+    /**
+     * Gets HSign by player.
+     *
+     * @param player Player.
+     * @return HSign.
+     */
+    @Nonnull
+    public static HSign getSignByPlayer(@Nonnull Player player) {
         return HSignHandler.getByPlayer(player);
     }
 
-    public static Optional<HSign> findSignByUID(UUID uid) {
+    /**
+     * Finds HSign by player UID.
+     *
+     * @param uid Player UID.
+     * @return HSign as optional.
+     */
+    @Nonnull
+    public static Optional<HSign> findSignByUID(@Nonnull UUID uid) {
         return HSignHandler.findByUID(uid);
     }
 
-    public static HSign getSignByUID(UUID uid) {
+    /**
+     * Gets HSign by player UID.
+     *
+     * @param uid Player UID.
+     * @return HSign.
+     */
+    @Nonnull
+    public static HSign getSignByUID(@Nonnull UUID uid) {
         return HSignHandler.getByUID(uid);
     }
 
+    /**
+     * Creates HSign.
+     *
+     * @param type  Sign type as Material.
+     * @param lines Lines of sign.
+     * @return Created HSign.
+     */
+    @Nonnull
     public static HSign createSign(@Nonnull Material type, @Nonnull String... lines) {
         return HSignHandler.create(type, lines);
     }
@@ -180,87 +335,217 @@ public static HSign createSign(@Nonnull Material type, @Nonnull String... lines)
     /*
     COMMAND
      */
-    public static HCommand registerCommand(String command, String... aliases) {
+
+    /**
+     * Registers a new command with aliases.
+     *
+     * @param command Command name.
+     * @param aliases Aliases.
+     * @return HCommand.
+     */
+    @Nonnull
+    public static HCommand registerCommand(@Nonnull String command, @Nonnull String... aliases) {
         return new HCommand(command, aliases).register();
     }
 
-    public static void registerCommand(HCommandExecutor... executors) {
-        Arrays.asList(executors).forEach(HCommandExecutor::register);
+    /**
+     * Registers command executors.
+     *
+     * @param executors Command executors.
+     */
+    public static void registerCommands(@Nonnull HCommandExecutor... executors) {
+        Arrays.asList(Objects.requireNonNull(executors, "executors cannot be null!")).forEach(HCommandExecutor::register);
     }
 
 
     /*
     PACKET
      */
-    public static void sendPacket(Player player, Object packet) {
-        HPacketHandler.getContent().get(player).send(packet);
+
+    /**
+     * Sends packet to players
+     *
+     * @param player Player.
+     * @param packet Packet.
+     */
+    public static void sendPacket(@Nonnull Player player, @Nonnull Object packet) {
+        HCore.sendPacket(player, new Object[]{packet});
     }
 
-    public static void sendPacket(Player player, Object... packets) {
-        HPacketHandler.getContent().get(player).send(packets);
+    /**
+     * Sends packets to player.
+     *
+     * @param player  Player.
+     * @param packets Packets.
+     */
+    public static void sendPacket(@Nonnull Player player, @Nonnull Object... packets) {
+        HPacketHandler.getContent().get(Objects.requireNonNull(player, "player cannot be null!")).send(packets);
     }
 
-    public static void sendPacket(Collection<Player> players, Object packet) {
-        players.forEach(player -> HCore.sendPacket(player, packet));
+    /**
+     * Sends packet to player list.
+     *
+     * @param players Player list.
+     * @param packet  Packet.
+     */
+    public static void sendPacket(@Nonnull Collection<Player> players, @Nonnull Object packet) {
+        HCore.sendPacket(players, new Object[]{packet});
     }
 
-    public static void sendPacket(Collection<Player> players, Object... packets) {
-        players.forEach(player -> HCore.sendPacket(player, packets));
+    /**
+     * Sends packets to player list.
+     *
+     * @param players Player list.
+     * @param packets Packets.
+     */
+    public static void sendPacket(@Nonnull Collection<Player> players, @Nonnull Object... packets) {
+        Objects.requireNonNull(players, "players cannot be null!").forEach(player -> HCore.sendPacket(player, packets));
     }
 
 
     /*
     PARTICLE
      */
-    public static void playParticle(Player player, Location location, HParticle hParticle) {
-        HParticleAPI.play(player, location, hParticle);
+
+    /**
+     * Plays particle for player.
+     *
+     * @param player   Player.
+     * @param location Location.
+     * @param particle HParticle class.
+     */
+    public static void playParticle(@Nonnull Player player, @Nonnull Location location, @Nonnull HParticle particle) {
+        HParticleAPI.play(player, location, particle);
     }
 
-    public static void playParticle(Collection<Player> players, Location location, HParticle hParticle) {
-        HParticleAPI.play(players, location, hParticle);
+    /**
+     * Plays particle for players.
+     *
+     * @param players  Players.
+     * @param location Location.
+     * @param particle HParticle class.
+     */
+    public static void playParticle(@Nonnull Collection<Player> players, @Nonnull Location location, @Nonnull HParticle particle) {
+        HParticleAPI.play(players, location, particle);
     }
 
 
     /*
     MESSAGE
      */
-    public static void sendTitle(Player player, HTitle hTitle) {
+
+    /**
+     * Sends title to player.
+     *
+     * @param player Player.
+     * @param hTitle HTitle class.
+     */
+    public static void sendTitle(@Nonnull Player player, @Nonnull HTitle hTitle) {
         HMessageAPI.sendTitle(player, hTitle);
     }
 
-    public static void sendTitle(Player player, String title, String subTitle) {
+    /**
+     * Sends title to player.
+     *
+     * @param player   Player.
+     * @param title    Title.
+     * @param subTitle Subtitle.
+     */
+    public static void sendTitle(@Nonnull Player player, @Nonnull String title, @Nonnull String subTitle) {
         HMessageAPI.sendTitle(player, title, subTitle);
     }
 
-    public static void sendTitle(Player player, String title, String subTitle, int stay, int fadein, int fadeout) {
+    /**
+     * Sends title to player.
+     *
+     * @param player   Player.
+     * @param title    Title.
+     * @param subTitle Subtitle.
+     * @param stay     Stay time.
+     * @param fadein   Fade in time.
+     * @param fadeout  Fade out time.
+     */
+    public static void sendTitle(@Nonnull Player player, @Nonnull String title, @Nonnull String subTitle, int stay, int fadein, int fadeout) {
         HMessageAPI.sendTitle(player, title, subTitle, stay, fadein, fadeout);
     }
 
-    public static void sendTitle(Collection<Player> players, HTitle hTitle) {
+    /**
+     * Sends title to players.
+     *
+     * @param players Players.
+     * @param hTitle  HTitle class.
+     */
+    public static void sendTitle(@Nonnull Collection<Player> players, @Nonnull HTitle hTitle) {
         HMessageAPI.sendTitle(players, hTitle);
     }
 
-    public static void sendTitle(Collection<Player> players, String title, String subTitle) {
+    /**
+     * Sends title to players.
+     *
+     * @param players  Players.
+     * @param title    Title.
+     * @param subTitle Subtitle.
+     */
+    public static void sendTitle(@Nonnull Collection<Player> players, @Nonnull String title, @Nonnull String subTitle) {
         HMessageAPI.sendTitle(players, title, subTitle);
     }
 
-    public static void sendTitle(Collection<Player> players, String title, String subTitle, int stay, int fadein, int fadeout) {
+    /**
+     * Sends title to players.
+     *
+     * @param players  Players.
+     * @param title    Title.
+     * @param subTitle Subtitle.
+     * @param stay     Stay time.
+     * @param fadein   Fade in time.
+     * @param fadeout  Fade out time.
+     */
+    public static void sendTitle(@Nonnull Collection<Player> players, @Nonnull String title, @Nonnull String subTitle, int stay, int fadein, int fadeout) {
         HMessageAPI.sendTitle(players, title, subTitle, stay, fadein, fadeout);
     }
 
-    public static void sendActionBar(Player player, String text) {
+    /**
+     * Sends action bar to player.
+     *
+     * @param player Player.
+     * @param text   Text.
+     */
+    public static void sendActionBar(@Nonnull Player player, @Nonnull String text) {
         HMessageAPI.sendActionBar(player, text);
     }
 
-    public static void sendActionBar(Collection<Player> players, String text) {
+    /**
+     * Sends action bar to players.
+     *
+     * @param players Players.
+     * @param text    Text.
+     */
+    public static void sendActionBar(@Nonnull Collection<Player> players, @Nonnull String text) {
         HMessageAPI.sendActionBar(players, text);
     }
 
+    /**
+     * Creates bossbar.
+     *
+     * @param title Title.
+     * @param color Color.
+     * @param style Style.
+     * @param flags Flags.
+     * @return New instance of HBossBar.
+     */
     public static HBossBar createBossBar(@Nonnull String title, @Nonnull HBarColor color, @Nonnull HBarStyle style, @Nonnull HBarFlag... flags) {
         return HMessageAPI.createBossBar(title, color, style, flags);
     }
 
-    public static HBossBar createBossBar(String title, HBarColor color, HBarStyle style) {
+    /**
+     * Creates bossbar.
+     *
+     * @param title Title.
+     * @param color Color.
+     * @param style Style.
+     * @return New instance of HBossBar.
+     */
+    public static HBossBar createBossBar(@Nonnull String title, @Nonnull HBarColor color, @Nonnull HBarStyle style) {
         return HMessageAPI.createBossBar(title, color, style);
     }
 
@@ -268,22 +553,62 @@ public static HBossBar createBossBar(String title, HBarColor color, HBarStyle st
     /*
     WORLD BORDER
      */
+
+    /**
+     * Gets values as safe.
+     *
+     * @return Values.
+     */
+    @Nonnull
     public static Collection<HWorldBorder> getBorderValuesSafe() {
         return HWorldBorderHandler.getValuesSafe();
     }
 
+    /**
+     * Gets values.
+     *
+     * @return Values.
+     */
+    @Nonnull
     public static Collection<HWorldBorder> getBorderValues() {
         return HWorldBorderHandler.getValues();
     }
 
-    public static Optional<HWorldBorder> findBorderByPlayer(Player player) {
+    /**
+     * Finds world border from player.
+     *
+     * @param player Player.
+     * @return HWorldBorder from player as optional.
+     */
+    @Nonnull
+    public static Optional<HWorldBorder> findBorderByPlayer(@Nonnull Player player) {
         return HWorldBorderHandler.findByPlayer(player);
     }
 
-    public static HWorldBorder getBorderByPlayer(Player player) {
+    /**
+     * Gets world border from player.
+     *
+     * @param player Player.
+     * @return HWorldBorder from player.
+     */
+    @Nonnull
+    public static HWorldBorder getBorderByPlayer(@Nonnull Player player) {
         return HWorldBorderHandler.getByPlayer(player);
     }
 
+    /**
+     * Creates world border.
+     *
+     * @param location        Center location.
+     * @param size            Size of world border.
+     * @param damageAmount    Damage amount.
+     * @param damageBuffer    Damage buffer.
+     * @param warningDistance Warning distance.
+     * @param warningTime     Warning time.
+     * @param color           Color of border.
+     * @return Created world border.
+     */
+    @Nonnull
     public static HWorldBorder createBorder(@Nonnull Location location, double size, double damageAmount, double damageBuffer, int warningDistance, int warningTime, @Nonnull HBorderColor color) {
         return HWorldBorderHandler.create(location, size, damageAmount, damageBuffer, warningDistance, warningTime, color);
     }
@@ -292,44 +617,100 @@ public static HWorldBorder createBorder(@Nonnull Location location, double size,
     /*
     HOLOGRAM
      */
+
+    /**
+     * Gets content as safe.
+     *
+     * @return holograms map.
+     */
     @Nonnull
     public static Map<String, HHologram> getHologramContentSafe() {
         return HHologramHandler.getContentSafe();
     }
 
+    /**
+     * Gets content.
+     *
+     * @return holograms map.
+     */
     @Nonnull
     public static Map<String, HHologram> getHologramContent() {
         return HHologramHandler.getContent();
     }
 
+    /**
+     * Gets holograms as safe.
+     *
+     * @return holograms.
+     */
+    @Nonnull
     public static Collection<HHologram> getHologramValuesSafe() {
         return HHologramHandler.getValuesSafe();
     }
 
+    /**
+     * Gets holograms.
+     *
+     * @return holograms.
+     */
+    @Nonnull
     public static Collection<HHologram> getHologramValues() {
         return HHologramHandler.getValues();
     }
 
+    /**
+     * Finds a created hologram
+     *
+     * @param id hologram id that you want
+     * @return hologram from id
+     */
     @Nonnull
     public static Optional<HHologram> findHologramByID(@Nonnull String id) {
         return HHologramHandler.findByID(id);
     }
 
+    /**
+     * Gets a created hologram
+     *
+     * @param id hologram id that you want
+     * @return hologram from id
+     */
     @Nonnull
     public static HHologram getHologramByID(@Nonnull String id) {
         return HHologramHandler.getByID(id);
     }
 
+    /**
+     * Creates a new hologram
+     *
+     * @param id       hologram id
+     * @param location location
+     * @param players  player list
+     * @return new hologram
+     */
     @Nonnull
-    public static HHologram createHologram(@Nonnull String id, @Nonnull Location location, @Nonnull Set<UUID> players) {
+    public static HHologram createHologram(@Nonnull String id, @Nonnull Location location, @Nullable Set<UUID> players) {
         return HHologramHandler.create(id, location, players);
     }
 
+    /**
+     * Creates a new hologram
+     *
+     * @param id       hologram id
+     * @param location location
+     * @return new hologram
+     */
     @Nonnull
     public static HHologram createHologram(@Nonnull String id, @Nonnull Location location) {
         return HHologramHandler.create(id, location);
     }
 
+    /**
+     * Deletes hologram by id
+     *
+     * @param id id of hologram
+     * @return hologram to be deleted
+     */
     @Nullable
     public static HHologram deleteHologram(@Nonnull String id) {
         return HHologramHandler.delete(id);
diff --git a/api/src/main/java/com/hakan/core/hologram/HHologramHandler.java b/api/src/main/java/com/hakan/core/hologram/HHologramHandler.java
index 9d8d3cc4..fc591225 100644
--- a/api/src/main/java/com/hakan/core/hologram/HHologramHandler.java
+++ b/api/src/main/java/com/hakan/core/hologram/HHologramHandler.java
@@ -45,6 +45,7 @@ public static Map<String, HHologram> getContent() {
      *
      * @return holograms.
      */
+    @Nonnull
     public static Collection<HHologram> getValuesSafe() {
         return new ArrayList<>(HHologramHandler.holograms.values());
     }
@@ -54,6 +55,7 @@ public static Collection<HHologram> getValuesSafe() {
      *
      * @return holograms.
      */
+    @Nonnull
     public static Collection<HHologram> getValues() {
         return HHologramHandler.holograms.values();
     }
diff --git a/api/src/main/java/com/hakan/core/ui/inventory/HInventory.java b/api/src/main/java/com/hakan/core/ui/inventory/HInventory.java
index 46d5f94d..39494d15 100644
--- a/api/src/main/java/com/hakan/core/ui/inventory/HInventory.java
+++ b/api/src/main/java/com/hakan/core/ui/inventory/HInventory.java
@@ -3,7 +3,6 @@
 import com.hakan.core.ui.inventory.item.ClickableItem;
 import com.hakan.core.ui.inventory.pagination.Page;
 import com.hakan.core.ui.inventory.pagination.Pagination;
-import org.apache.commons.lang.Validate;
 import org.bukkit.Bukkit;
 import org.bukkit.Material;
 import org.bukkit.entity.Player;
@@ -29,7 +28,16 @@ public class HInventory {
     private final Set<Option> options;
     private final Map<Integer, ClickableItem> items;
 
-    public HInventory(String id, String title, int size, InventoryType type, Set<Option> options) {
+    /**
+     * Creates new instance of this class.
+     *
+     * @param id      ID of inventory.
+     * @param title   Title.
+     * @param size    Size.
+     * @param type    Inventory type.
+     * @param options Options.
+     */
+    public HInventory(@Nonnull String id, @Nonnull String title, int size, @Nonnull InventoryType type, @Nonnull Set<Option> options) {
         this.id = id;
         this.title = title;
         this.options = options;
@@ -43,7 +51,16 @@ public HInventory(String id, String title, int size, InventoryType type, Set<Opt
         this.onCreate(this);
     }
 
-    public HInventory(String id, String title, int size, InventoryType type) {
+    /**
+     * Creates new instance of this class
+     * with all options.
+     *
+     * @param id    ID of inventory.
+     * @param title Title.
+     * @param size  Size.
+     * @param type  Inventory type.
+     */
+    public HInventory(@Nonnull String id, @Nonnull String title, int size, @Nonnull InventoryType type) {
         this(id, title, size, type, new HashSet<>(Arrays.asList(Option.values())));
     }
 
@@ -103,8 +120,7 @@ public final int getSize() {
      * @return If UI contains option, returns true
      */
     public final boolean hasOption(@Nonnull Option option) {
-        Validate.notNull(option, "option cannot be null");
-        return this.options.contains(option);
+        return this.options.contains(Objects.requireNonNull(option, "option cannot be null!"));
     }
 
     /**
@@ -113,9 +129,9 @@ public final boolean hasOption(@Nonnull Option option) {
      * @param option enum HInventory.Option
      * @return instance of this class
      */
+    @Nonnull
     public final <T extends HInventory> T addOption(@Nonnull Option option) {
-        Validate.notNull(option, "option cannot be null");
-        this.options.add(option);
+        this.options.add(Objects.requireNonNull(option, "option cannot be null!"));
         return (T) this;
     }
 
@@ -125,9 +141,9 @@ public final <T extends HInventory> T addOption(@Nonnull Option option) {
      * @param option enum HInventory.Option
      * @return instance of this class
      */
+    @Nonnull
     public final <T extends HInventory> T removeOption(@Nonnull Option option) {
-        Validate.notNull(option, "option cannot be null");
-        this.options.remove(option);
+        this.options.remove(Objects.requireNonNull(option, "option cannot be null!"));
         return (T) this;
     }
 
@@ -198,7 +214,6 @@ public final <T extends HInventory> T setItem(int slot, @Nullable ClickableItem
      */
     @Nonnull
     public final <T extends HInventory> T setItem(int slot, @Nonnull ItemStack itemStack, @Nullable Consumer<InventoryClickEvent> consumer) {
-        Validate.notNull(itemStack, "itemstack cannot be null");
         return this.setItem(slot, new ClickableItem(itemStack, consumer));
     }
 
@@ -221,8 +236,8 @@ public final <T extends HInventory> T setItem(int slot, @Nonnull ItemStack itemS
      * @return instance of this class
      */
     @Nonnull
-    public final <T extends HInventory> T fillPage(Page page) {
-        this.pagination.setCurrentPage(page.getNumber());
+    public final <T extends HInventory> T fillPage(@Nonnull Page page) {
+        this.pagination.setCurrentPage(Objects.requireNonNull(page, "page cannot be null!").getNumber());
         return (T) this;
     }
 
@@ -309,7 +324,7 @@ public final <T extends HInventory> T fill(@Nonnull ItemStack itemStack) {
      */
     @Nonnull
     public final <T extends HInventory> T fillMaterial(@Nonnull Material material, boolean replaceWithItems) {
-        return this.fill(new ItemStack(material), replaceWithItems);
+        return this.fill(new ItemStack(Objects.requireNonNull(material, "material cannot be null!")), replaceWithItems);
     }
 
     /**
@@ -320,7 +335,7 @@ public final <T extends HInventory> T fillMaterial(@Nonnull Material material, b
      */
     @Nonnull
     public final <T extends HInventory> T fillMaterial(@Nonnull Material material) {
-        return this.fill(new ItemStack(material), true);
+        return this.fill(new ItemStack(Objects.requireNonNull(material, "material cannot be null!")), true);
     }
 
     /**
@@ -371,8 +386,8 @@ public final <T extends HInventory> T fillNull() {
      * @return instance of this class
      */
     @Nonnull
-    public <T extends HInventory> T refresh(Player player) {
-        this.onOpen(this, player);
+    public final <T extends HInventory> T refresh(@Nonnull Player player) {
+        this.onOpen(this, Objects.requireNonNull(player, "player cannot be null!"));
         return (T) this;
     }
 
@@ -383,8 +398,8 @@ public <T extends HInventory> T refresh(Player player) {
      * @return instance of this class
      */
     @Nonnull
-    public final <T extends HInventory> T open(Player player) {
-        HInventory hInventory = HInventoryHandler.findByPlayer(player).orElse(null);
+    public final <T extends HInventory> T open(@Nonnull Player player) {
+        HInventory hInventory = HInventoryHandler.findByPlayer(Objects.requireNonNull(player, "player cannot be null!")).orElse(null);
 
         if (hInventory == null || !hInventory.equals(this)) {
             player.openInventory(this.inventory);
@@ -402,21 +417,46 @@ public final <T extends HInventory> T open(Player player) {
      * @return instance of this class
      */
     @Nonnull
-    public final <T extends HInventory> T close(Player player) {
-        this.addOption(Option.CLOSABLE);
-        player.closeInventory();
+    public final <T extends HInventory> T close(@Nonnull Player player) {
+        Objects.requireNonNull(player, "player cannot be null!");
+
+        if (this.hasOption(Option.CLOSABLE)) {
+            player.closeInventory();
+        } else {
+            this.addOption(Option.CLOSABLE);
+            player.closeInventory();
+            this.removeOption(Option.CLOSABLE);
+        }
+
         return (T) this;
     }
 
-    public void onCreate(HInventory hInventory) {
+    /**
+     * This method run when inventory created.
+     *
+     * @param hInventory This class.
+     */
+    public void onCreate(@Nonnull HInventory hInventory) {
 
     }
 
-    public void onOpen(HInventory hInventory, Player player) {
+    /**
+     * This method run when inventory
+     * opened to any player.
+     *
+     * @param hInventory This class.
+     */
+    public void onOpen(@Nonnull HInventory hInventory, @Nonnull Player player) {
 
     }
 
-    public void onClose(HInventory hInventory, Player player) {
+    /**
+     * This method run when inventory
+     * closed from any player.
+     *
+     * @param hInventory This class.
+     */
+    public void onClose(@Nonnull HInventory hInventory, @Nonnull Player player) {
 
     }
 
diff --git a/api/src/main/java/com/hakan/core/ui/inventory/HInventoryHandler.java b/api/src/main/java/com/hakan/core/ui/inventory/HInventoryHandler.java
index 4e119b5b..3d0c0d1f 100644
--- a/api/src/main/java/com/hakan/core/ui/inventory/HInventoryHandler.java
+++ b/api/src/main/java/com/hakan/core/ui/inventory/HInventoryHandler.java
@@ -12,49 +12,118 @@
 import javax.annotation.Nonnull;
 import java.util.*;
 
+/**
+ * HInventoryHandler class to create
+ * and find HInventory.
+ */
 public final class HInventoryHandler {
 
     private static final Map<UUID, HInventory> inventoryMap = new HashMap<>();
 
-    public static void initialize(JavaPlugin plugin) {
+    /**
+     * Initializes the inventory system.
+     *
+     * @param plugin Main class of plugin.
+     */
+    public static void initialize(@Nonnull JavaPlugin plugin) {
         HListenerAdapter.register(new PlayerQuitListener(plugin),
                 new PluginDisableListener(plugin),
                 new InventoryClickListener(plugin),
                 new InventoryCloseListener(plugin));
     }
 
+
+    /**
+     * Gets content as safe.
+     *
+     * @return Content.
+     */
+    @Nonnull
     public static Map<UUID, HInventory> getContentSafe() {
         return new HashMap<>(HInventoryHandler.inventoryMap);
     }
 
+    /**
+     * Gets content.
+     *
+     * @return Content.
+     */
+    @Nonnull
     public static Map<UUID, HInventory> getContent() {
         return HInventoryHandler.inventoryMap;
     }
 
+    /**
+     * Gets values as safe.
+     *
+     * @return Values.
+     */
+    @Nonnull
     public static Collection<HInventory> getValuesSafe() {
         return new ArrayList<>(HInventoryHandler.inventoryMap.values());
     }
 
+    /**
+     * Gets values.
+     *
+     * @return Values.
+     */
+    @Nonnull
     public static Collection<HInventory> getValues() {
         return HInventoryHandler.inventoryMap.values();
     }
 
-    public static Optional<HInventory> findByPlayer(Player player) {
+    /**
+     * Finds HInventory by player.
+     *
+     * @param player Player.
+     * @return HInventory as optional.
+     */
+    @Nonnull
+    public static Optional<HInventory> findByPlayer(@Nonnull Player player) {
         return HInventoryHandler.findByUID(player.getUniqueId());
     }
 
-    public static HInventory getByPlayer(Player player) {
+    /**
+     * Gets HInventory by player.
+     *
+     * @param player Player.
+     * @return HInventory.
+     */
+    @Nonnull
+    public static HInventory getByPlayer(@Nonnull Player player) {
         return HInventoryHandler.findByPlayer(player).orElseThrow(() -> new NullPointerException("this player doesn't have a inventory!"));
     }
 
-    public static Optional<HInventory> findByUID(UUID uid) {
-        return Optional.ofNullable(HInventoryHandler.inventoryMap.get(uid));
+    /**
+     * Finds HInventory by UID.
+     *
+     * @param uid Player UID.
+     * @return HInventory as optional.
+     */
+    @Nonnull
+    public static Optional<HInventory> findByUID(@Nonnull UUID uid) {
+        return Optional.ofNullable(HInventoryHandler.inventoryMap.get(Objects.requireNonNull(uid, "UID cannot be null!")));
     }
 
-    public static HInventory getByUID(UUID uid) {
+    /**
+     * Gets HInventory by UID.
+     *
+     * @param uid Player UId.
+     * @return HInventory.
+     */
+    @Nonnull
+    public static HInventory getByUID(@Nonnull UUID uid) {
         return HInventoryHandler.findByUID(uid).orElseThrow(() -> new NullPointerException("this player doesn't have a inventory!"));
     }
 
+    /**
+     * Creates builder with ID.
+     *
+     * @param id ID.
+     * @return HInventoryBuilder.
+     */
+    @Nonnull
     public static HInventoryBuilder builder(@Nonnull String id) {
         return new HInventoryBuilder(id);
     }
diff --git a/api/src/main/java/com/hakan/core/ui/inventory/builder/HInventoryBuilder.java b/api/src/main/java/com/hakan/core/ui/inventory/builder/HInventoryBuilder.java
index 4a10e799..4d02a1d8 100644
--- a/api/src/main/java/com/hakan/core/ui/inventory/builder/HInventoryBuilder.java
+++ b/api/src/main/java/com/hakan/core/ui/inventory/builder/HInventoryBuilder.java
@@ -6,8 +6,13 @@
 import javax.annotation.Nonnull;
 import java.util.Arrays;
 import java.util.HashSet;
+import java.util.Objects;
 import java.util.Set;
 
+/**
+ * HInventoryBuilder class to
+ * build HInventory.
+ */
 public final class HInventoryBuilder {
 
     private int size;
@@ -16,59 +21,117 @@ public final class HInventoryBuilder {
     private InventoryType type;
     private Set<HInventory.Option> options;
 
-    public HInventoryBuilder(String id) {
-        this.id = id;
+    /**
+     * Creates new instance of this class.
+     *
+     * @param id ID.
+     */
+    public HInventoryBuilder(@Nonnull String id) {
+        this.id = Objects.requireNonNull(id, "id cannot be null!");
         this.options(HInventory.Option.values());
     }
 
+    /**
+     * Sets id.
+     *
+     * @param id ID.
+     * @return This class.
+     */
     @Nonnull
     public HInventoryBuilder id(@Nonnull String id) {
-        this.id = id;
+        this.id = Objects.requireNonNull(id, "id cannot be null!");
         return this;
     }
 
+    /**
+     * Sets title.
+     *
+     * @param title Title.
+     * @return This class.
+     */
     @Nonnull
     public HInventoryBuilder title(@Nonnull String title) {
-        this.title = title;
+        this.title = Objects.requireNonNull(title, "title cannot be null!");
         return this;
     }
 
+    /**
+     * Sets inventory type.
+     *
+     * @param type Inventory type.
+     * @return This class.
+     */
     @Nonnull
     public HInventoryBuilder type(@Nonnull InventoryType type) {
-        this.type = type;
+        this.type = Objects.requireNonNull(type, "inventory type cannot be null!");
         return this;
     }
 
+    /**
+     * Sets size.
+     *
+     * @param size Size.
+     * @return This class.
+     */
     @Nonnull
     public HInventoryBuilder size(int size) {
         this.size = size;
         return this;
     }
 
+    /**
+     * Sets options.
+     *
+     * @param options Options.
+     * @return This class.
+     */
     @Nonnull
-    public HInventoryBuilder options(Set<HInventory.Option> options) {
-        this.options = options;
+    public HInventoryBuilder options(@Nonnull Set<HInventory.Option> options) {
+        this.options = Objects.requireNonNull(options, "options cannot be null!");
         return this;
     }
 
+    /**
+     * Sets options.
+     *
+     * @param options Options.
+     * @return This class.
+     */
     @Nonnull
-    public HInventoryBuilder options(HInventory.Option... options) {
-        this.options = new HashSet<>(Arrays.asList(options));
+    public HInventoryBuilder options(@Nonnull HInventory.Option... options) {
+        this.options = new HashSet<>(Arrays.asList(Objects.requireNonNull(options, "options cannot be null!")));
         return this;
     }
 
+    /**
+     * Adds option.
+     *
+     * @param option Option.
+     * @return This class.
+     */
     @Nonnull
-    public HInventoryBuilder addOption(HInventory.Option option) {
-        this.options.add(option);
+    public HInventoryBuilder addOption(@Nonnull HInventory.Option option) {
+        this.options.add(Objects.requireNonNull(option, "option cannot be null!"));
         return this;
     }
 
+    /**
+     * Removes option.
+     *
+     * @param option Option.
+     * @return This class.
+     */
     @Nonnull
-    public HInventoryBuilder removeOption(HInventory.Option option) {
-        this.options.remove(option);
+    public HInventoryBuilder removeOption(@Nonnull HInventory.Option option) {
+        this.options.remove(Objects.requireNonNull(option, "option cannot be null!"));
         return this;
     }
 
+    /**
+     * Builds HInventory class.
+     *
+     * @return HInventory.
+     */
     @Nonnull
     public HInventory build() {
         return new HInventory(this.id, this.title, this.size, this.type, this.options);
diff --git a/api/src/main/java/com/hakan/core/ui/inventory/item/ClickableItem.java b/api/src/main/java/com/hakan/core/ui/inventory/item/ClickableItem.java
index 8ff25056..9b0e83c8 100644
--- a/api/src/main/java/com/hakan/core/ui/inventory/item/ClickableItem.java
+++ b/api/src/main/java/com/hakan/core/ui/inventory/item/ClickableItem.java
@@ -8,20 +8,41 @@
 import java.util.Objects;
 import java.util.function.Consumer;
 
+/**
+ * ClickableItem class.
+ */
 public final class ClickableItem {
 
     private final ItemStack item;
     private final Consumer<InventoryClickEvent> click;
 
+    /**
+     * Creates new instance of this class.
+     *
+     * @param item  ItemStack.
+     * @param click Click consumer.
+     */
     public ClickableItem(@Nonnull ItemStack item, @Nullable Consumer<InventoryClickEvent> click) {
         this.item = Objects.requireNonNull(item, "item cannot be null!");
         this.click = click;
     }
 
+    /**
+     * Gets item stack.
+     *
+     * @return Item stack.
+     */
+    @Nonnull
     public ItemStack getItem() {
         return this.item;
     }
 
+    /**
+     * Gets click consumer.
+     *
+     * @return Click consumer.
+     */
+    @Nullable
     public Consumer<InventoryClickEvent> getClick() {
         return this.click;
     }
diff --git a/api/src/main/java/com/hakan/core/ui/inventory/listeners/bukkit/PlayerQuitListener.java b/api/src/main/java/com/hakan/core/ui/inventory/listeners/bukkit/PlayerQuitListener.java
index c1f371ae..6fb20cb4 100644
--- a/api/src/main/java/com/hakan/core/ui/inventory/listeners/bukkit/PlayerQuitListener.java
+++ b/api/src/main/java/com/hakan/core/ui/inventory/listeners/bukkit/PlayerQuitListener.java
@@ -9,14 +9,27 @@
 
 import javax.annotation.Nonnull;
 
-public class PlayerQuitListener extends HListenerAdapter {
+/**
+ * Player quit listener class.
+ */
+public final class PlayerQuitListener extends HListenerAdapter {
 
+    /**
+     * Creates new instance of this class.
+     *
+     * @param plugin Main class of plugin.
+     */
     public PlayerQuitListener(@Nonnull JavaPlugin plugin) {
         super(plugin);
     }
 
+    /**
+     * Quit event.
+     *
+     * @param event Event.
+     */
     @EventHandler
-    public void onQuit(PlayerQuitEvent event) {
+    public void onQuit(@Nonnull PlayerQuitEvent event) {
         Player player = event.getPlayer();
         HInventoryHandler.findByPlayer(player)
                 .ifPresent(hInventory -> hInventory.close(player));
diff --git a/api/src/main/java/com/hakan/core/ui/inventory/listeners/bukkit/PluginDisableListener.java b/api/src/main/java/com/hakan/core/ui/inventory/listeners/bukkit/PluginDisableListener.java
index a208d596..5a4c8c5a 100644
--- a/api/src/main/java/com/hakan/core/ui/inventory/listeners/bukkit/PluginDisableListener.java
+++ b/api/src/main/java/com/hakan/core/ui/inventory/listeners/bukkit/PluginDisableListener.java
@@ -9,14 +9,27 @@
 
 import javax.annotation.Nonnull;
 
-public class PluginDisableListener extends HListenerAdapter {
+/**
+ * Plugin disable listener class.
+ */
+public final class PluginDisableListener extends HListenerAdapter {
 
+    /**
+     * Creates new instance of this class.
+     *
+     * @param plugin Main class of plugin.
+     */
     public PluginDisableListener(@Nonnull JavaPlugin plugin) {
         super(plugin);
     }
 
+    /**
+     * Plugin disable event.
+     *
+     * @param event Event.
+     */
     @EventHandler
-    public void onQuit(PluginDisableEvent event) {
+    public void onQuit(@Nonnull PluginDisableEvent event) {
         if (!event.getPlugin().equals(this.plugin))
             return;
 
diff --git a/api/src/main/java/com/hakan/core/ui/inventory/listeners/inventory/InventoryClickListener.java b/api/src/main/java/com/hakan/core/ui/inventory/listeners/inventory/InventoryClickListener.java
index e8bb97dd..8a642b0c 100644
--- a/api/src/main/java/com/hakan/core/ui/inventory/listeners/inventory/InventoryClickListener.java
+++ b/api/src/main/java/com/hakan/core/ui/inventory/listeners/inventory/InventoryClickListener.java
@@ -12,14 +12,28 @@
 import javax.annotation.Nonnull;
 import java.util.Optional;
 
+/**
+ * This class handles hInventory click
+ * events.
+ */
 public final class InventoryClickListener extends HListenerAdapter {
 
+    /**
+     * Creates new instance of this class.
+     *
+     * @param plugin Main class of plugin.
+     */
     public InventoryClickListener(@Nonnull JavaPlugin plugin) {
         super(plugin);
     }
 
+    /**
+     * Inventory click event.
+     *
+     * @param event Event.
+     */
     @EventHandler
-    public void onClick(InventoryClickEvent event) {
+    public void onClick(@Nonnull InventoryClickEvent event) {
         if (event.getClick() == ClickType.UNKNOWN) {
             event.setCancelled(true);
             return;
diff --git a/api/src/main/java/com/hakan/core/ui/inventory/listeners/inventory/InventoryCloseListener.java b/api/src/main/java/com/hakan/core/ui/inventory/listeners/inventory/InventoryCloseListener.java
index 30a71895..85cbdc3d 100644
--- a/api/src/main/java/com/hakan/core/ui/inventory/listeners/inventory/InventoryCloseListener.java
+++ b/api/src/main/java/com/hakan/core/ui/inventory/listeners/inventory/InventoryCloseListener.java
@@ -11,14 +11,28 @@
 
 import javax.annotation.Nonnull;
 
-public class InventoryCloseListener extends HListenerAdapter {
+/**
+ * This class handles inventory
+ * close event for CLOSABLE option.
+ */
+public final class InventoryCloseListener extends HListenerAdapter {
 
+    /**
+     * Creates new instance of this class.
+     *
+     * @param plugin Main class of plugin.
+     */
     public InventoryCloseListener(@Nonnull JavaPlugin plugin) {
         super(plugin);
     }
 
+    /**
+     * Inventory close event.
+     *
+     * @param event Event.
+     */
     @EventHandler
-    public void onClose(InventoryCloseEvent event) {
+    public void onClose(@Nonnull InventoryCloseEvent event) {
         Player player = (Player) event.getPlayer();
 
         HInventoryHandler.findByPlayer(player).ifPresent(hInventory -> {
diff --git a/api/src/main/java/com/hakan/core/ui/inventory/pagination/Page.java b/api/src/main/java/com/hakan/core/ui/inventory/pagination/Page.java
index 0482d4a9..d49dc746 100644
--- a/api/src/main/java/com/hakan/core/ui/inventory/pagination/Page.java
+++ b/api/src/main/java/com/hakan/core/ui/inventory/pagination/Page.java
@@ -2,23 +2,43 @@
 
 import com.hakan.core.ui.inventory.item.ClickableItem;
 
+import javax.annotation.Nonnull;
 import java.util.HashMap;
 import java.util.Map;
 
-public class Page {
+/**
+ * Page class.
+ */
+public final class Page {
 
     private final int number;
     private final Map<Integer, ClickableItem> items;
 
+    /**
+     * Creates new instance of this class.
+     *
+     * @param number Number of page.
+     */
     public Page(int number) {
         this.number = number;
         this.items = new HashMap<>();
     }
 
+    /**
+     * Gets number of page.
+     *
+     * @return Number of page.
+     */
     public int getNumber() {
         return this.number;
     }
 
+    /**
+     * Gets item list in page.
+     *
+     * @return Item list in page.
+     */
+    @Nonnull
     public Map<Integer, ClickableItem> getItems() {
         return this.items;
     }
diff --git a/api/src/main/java/com/hakan/core/ui/inventory/pagination/Pagination.java b/api/src/main/java/com/hakan/core/ui/inventory/pagination/Pagination.java
index d51700df..44486953 100644
--- a/api/src/main/java/com/hakan/core/ui/inventory/pagination/Pagination.java
+++ b/api/src/main/java/com/hakan/core/ui/inventory/pagination/Pagination.java
@@ -5,14 +5,15 @@
 import org.bukkit.Material;
 import org.bukkit.inventory.ItemStack;
 
-import java.util.ArrayList;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.Optional;
+import javax.annotation.Nonnull;
+import java.util.*;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
-public class Pagination {
+/**
+ * Pagination class.
+ */
+public final class Pagination {
 
     private final HInventory inventory;
 
@@ -21,78 +22,173 @@ public class Pagination {
     private List<ClickableItem> items;
     private List<Page> pages;
 
-    public Pagination(HInventory inventory) {
+    /**
+     * Creates new instance of this class.
+     *
+     * @param inventory Parent inventory.
+     */
+    public Pagination(@Nonnull HInventory inventory) {
+        this.inventory = Objects.requireNonNull(inventory, "inventory cannot be null!");
         this.currentPage = 0;
-        this.inventory = inventory;
         this.slots = new ArrayList<>();
         this.items = new ArrayList<>();
         this.pages = new LinkedList<>();
         this.pages.add(new Page(0));
     }
 
+    /**
+     * Gets parent inventory.
+     *
+     * @return Parent inventory.
+     */
+    @Nonnull
     public HInventory getInventory() {
         return this.inventory;
     }
 
+    /**
+     * Gets page list as safe.
+     *
+     * @return Page list.
+     */
+    @Nonnull
     public List<Page> getPagesSafe() {
         return new ArrayList<>(this.pages);
     }
 
+    /**
+     * Gets item list as safe.
+     *
+     * @return Item list.
+     */
+    @Nonnull
     public List<ClickableItem> getItemsSafe() {
         return new ArrayList<>(this.items);
     }
 
-    public void setItems(List<ClickableItem> clickableItems) {
-        this.items = clickableItems;
+    /**
+     * Sets clickable item list.
+     *
+     * @param clickableItems Clickable item list
+     */
+    public void setItems(@Nonnull List<ClickableItem> clickableItems) {
+        this.items = Objects.requireNonNull(clickableItems, "clickable items cannot be null!");
         this.pages = this.createPages();
     }
 
+    /**
+     * Gets slots.
+     *
+     * @return Slots.
+     */
+    @Nonnull
     public List<Integer> getSlots() {
         return this.slots;
     }
 
+    /**
+     * Sets slots min to max.
+     *
+     * @param min First.
+     * @param max Last.
+     */
     public void setSlots(int min, int max) {
         this.setSlots(IntStream.rangeClosed(min, max).boxed().collect(Collectors.toList()));
     }
 
-    public void setSlots(List<Integer> ints) {
-        this.slots = ints;
+    /**
+     * Sets slots.
+     *
+     * @param ints Slots.
+     */
+    public void setSlots(@Nonnull List<Integer> ints) {
+        this.slots = Objects.requireNonNull(ints, "slots cannot be null!");
         this.pages = this.createPages();
     }
 
+    /**
+     * Finds page from page number.
+     *
+     * @param page Page as number.
+     * @return Page.
+     */
+    @Nonnull
     public Optional<Page> findPage(int page) {
         return Optional.ofNullable(this.pages.get(page));
     }
 
+    /**
+     * Gets page from page number.
+     *
+     * @param page Page number.
+     * @return Page.
+     */
+    @Nonnull
     public Page getPage(int page) {
         return this.findPage(page).orElseThrow(() -> new NullPointerException("there is no page at number(" + page + ")!"));
     }
 
+    /**
+     * Gets current page number.
+     *
+     * @return Current page number.
+     */
     public int getCurrentPage() {
         return this.currentPage;
     }
 
+    /**
+     * Sets current page number.
+     *
+     * @param page Current page number.
+     */
     public void setCurrentPage(int page) {
         this.setCurrentPage(this.getPage(page));
     }
 
-    public void setCurrentPage(Page page) {
-        this.currentPage = page.getNumber();
+    /**
+     * Changes current page and
+     * fill the inventory.
+     *
+     * @param page Page.
+     */
+    public void setCurrentPage(@Nonnull Page page) {
+        this.currentPage = Objects.requireNonNull(page, "page cannot be null!").getNumber();
         page.getItems().forEach(this.inventory::setItem);
     }
 
+    /**
+     * Gets next page number.
+     *
+     * @return Next page number.
+     */
     public int getNextPage() {
         return this.currentPage + 1;
     }
 
+    /**
+     * Gets previous page number.
+     *
+     * @return Previous page number.
+     */
     public int getPreviousPage() {
         return this.currentPage - 1;
     }
 
+    /**
+     * Gets first page number.
+     *
+     * @return First page number
+     */
     public int getFirstPage() {
         return 0;
     }
 
+    /**
+     * Gets last page number.
+     *
+     * @return Last page number.
+     */
     public int getLastPage() {
         double itemSize = this.items.size();
         if (itemSize == 0) return 0;
@@ -103,14 +199,30 @@ public int getLastPage() {
         return (int) (Math.ceil(itemSize / slotSize) - 1);
     }
 
+    /**
+     * Checks the current page is first page.
+     *
+     * @return If the current page is first page, returns true.
+     */
     public boolean isFirstPage() {
         return this.currentPage == this.getFirstPage();
     }
 
+    /**
+     * Checks the current page is last page.
+     *
+     * @return If the current page is last page, returns true.
+     */
     public boolean isLastPage() {
         return this.currentPage == this.getLastPage();
     }
 
+    /**
+     * Creates pages from this.items list.
+     *
+     * @return Pages as list.
+     */
+    @Nonnull
     private List<Page> createPages() {
         int clickableItemSize = this.items.size();
         int itemSlotSize = this.slots.size();
diff --git a/nms/1_8_R3/src/main/java/com/hakan/core/message/bossbar/HBossBar_v1_8_R3.java b/nms/1_8_R3/src/main/java/com/hakan/core/message/bossbar/HBossBar_v1_8_R3.java
index 272465f7..756f5036 100644
--- a/nms/1_8_R3/src/main/java/com/hakan/core/message/bossbar/HBossBar_v1_8_R3.java
+++ b/nms/1_8_R3/src/main/java/com/hakan/core/message/bossbar/HBossBar_v1_8_R3.java
@@ -1,6 +1,5 @@
 package com.hakan.core.message.bossbar;
 
-import org.apache.commons.lang.Validate;
 import org.bukkit.entity.Player;
 
 import javax.annotation.Nonnull;