From 52ecf3a83d9a0ce736d7a357f319168712778706 Mon Sep 17 00:00:00 2001
From: xISRAPILx <israpil.akhmedov.27@gmail.com>
Date: Sat, 20 Aug 2022 00:53:03 +0300
Subject: [PATCH] Make Nukkit more kotlin friendly: Commands

---
 pom.xml                                                      | 5 +++++
 src/main/java/cn/nukkit/command/Command.java                 | 3 ++-
 src/main/java/cn/nukkit/command/FormattedCommandAlias.java   | 3 ++-
 src/main/java/cn/nukkit/command/PluginCommand.java           | 3 ++-
 src/main/java/cn/nukkit/command/defaults/BanCommand.java     | 3 ++-
 src/main/java/cn/nukkit/command/defaults/BanIpCommand.java   | 3 ++-
 src/main/java/cn/nukkit/command/defaults/BanListCommand.java | 3 ++-
 .../java/cn/nukkit/command/defaults/DebugPasteCommand.java   | 4 +++-
 .../cn/nukkit/command/defaults/DefaultGamemodeCommand.java   | 3 ++-
 src/main/java/cn/nukkit/command/defaults/DeopCommand.java    | 3 ++-
 .../java/cn/nukkit/command/defaults/DifficultyCommand.java   | 3 ++-
 src/main/java/cn/nukkit/command/defaults/EffectCommand.java  | 3 ++-
 src/main/java/cn/nukkit/command/defaults/EnchantCommand.java | 3 ++-
 .../java/cn/nukkit/command/defaults/GamemodeCommand.java     | 3 ++-
 .../java/cn/nukkit/command/defaults/GameruleCommand.java     | 3 ++-
 .../cn/nukkit/command/defaults/GarbageCollectorCommand.java  | 3 ++-
 src/main/java/cn/nukkit/command/defaults/GiveCommand.java    | 3 ++-
 src/main/java/cn/nukkit/command/defaults/HelpCommand.java    | 3 ++-
 src/main/java/cn/nukkit/command/defaults/KickCommand.java    | 3 ++-
 src/main/java/cn/nukkit/command/defaults/KillCommand.java    | 3 ++-
 src/main/java/cn/nukkit/command/defaults/ListCommand.java    | 3 ++-
 src/main/java/cn/nukkit/command/defaults/MeCommand.java      | 3 ++-
 src/main/java/cn/nukkit/command/defaults/OpCommand.java      | 3 ++-
 src/main/java/cn/nukkit/command/defaults/PardonCommand.java  | 3 ++-
 .../java/cn/nukkit/command/defaults/PardonIpCommand.java     | 3 ++-
 .../java/cn/nukkit/command/defaults/ParticleCommand.java     | 3 ++-
 src/main/java/cn/nukkit/command/defaults/PluginsCommand.java | 3 ++-
 src/main/java/cn/nukkit/command/defaults/ReloadCommand.java  | 3 ++-
 src/main/java/cn/nukkit/command/defaults/SaveCommand.java    | 3 ++-
 src/main/java/cn/nukkit/command/defaults/SaveOffCommand.java | 3 ++-
 src/main/java/cn/nukkit/command/defaults/SaveOnCommand.java  | 3 ++-
 src/main/java/cn/nukkit/command/defaults/SayCommand.java     | 3 ++-
 src/main/java/cn/nukkit/command/defaults/SeedCommand.java    | 3 ++-
 .../cn/nukkit/command/defaults/SetWorldSpawnCommand.java     | 3 ++-
 .../java/cn/nukkit/command/defaults/SpawnpointCommand.java   | 3 ++-
 src/main/java/cn/nukkit/command/defaults/StatusCommand.java  | 3 ++-
 src/main/java/cn/nukkit/command/defaults/StopCommand.java    | 3 ++-
 .../java/cn/nukkit/command/defaults/TeleportCommand.java     | 3 ++-
 src/main/java/cn/nukkit/command/defaults/TellCommand.java    | 3 ++-
 src/main/java/cn/nukkit/command/defaults/TimeCommand.java    | 3 ++-
 src/main/java/cn/nukkit/command/defaults/TimingsCommand.java | 3 ++-
 src/main/java/cn/nukkit/command/defaults/TitleCommand.java   | 3 ++-
 src/main/java/cn/nukkit/command/defaults/VersionCommand.java | 3 ++-
 src/main/java/cn/nukkit/command/defaults/WeatherCommand.java | 3 ++-
 .../java/cn/nukkit/command/defaults/WhitelistCommand.java    | 3 ++-
 src/main/java/cn/nukkit/command/defaults/XpCommand.java      | 3 ++-
 src/main/java/cn/nukkit/command/simple/SimpleCommand.java    | 3 ++-
 47 files changed, 98 insertions(+), 46 deletions(-)

diff --git a/pom.xml b/pom.xml
index 32be8b47aab..e6fd38b88b2 100644
--- a/pom.xml
+++ b/pom.xml
@@ -167,6 +167,11 @@
             <version>${jline.version}</version>
             <scope>compile</scope>
         </dependency>
+        <dependency>
+            <groupId>org.jetbrains</groupId>
+            <artifactId>annotations</artifactId>
+            <version>23.0.0</version>
+        </dependency>
     </dependencies>
 
     <build>
diff --git a/src/main/java/cn/nukkit/command/Command.java b/src/main/java/cn/nukkit/command/Command.java
index fbbd4954eb7..928264335bf 100644
--- a/src/main/java/cn/nukkit/command/Command.java
+++ b/src/main/java/cn/nukkit/command/Command.java
@@ -9,6 +9,7 @@
 import cn.nukkit.utils.TextFormat;
 import co.aikar.timings.Timing;
 import co.aikar.timings.Timings;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.*;
 
@@ -135,7 +136,7 @@ public Map<String, CommandOverload> getOverloads() {
         return this.commandData.overloads;
     }
 
-    public abstract boolean execute(CommandSender sender, String commandLabel, String[] args);
+    public abstract boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args);
 
     public String getName() {
         return name;
diff --git a/src/main/java/cn/nukkit/command/FormattedCommandAlias.java b/src/main/java/cn/nukkit/command/FormattedCommandAlias.java
index 8e84261e176..f52fa152ce7 100644
--- a/src/main/java/cn/nukkit/command/FormattedCommandAlias.java
+++ b/src/main/java/cn/nukkit/command/FormattedCommandAlias.java
@@ -4,6 +4,7 @@
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.utils.MainLogger;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -27,7 +28,7 @@ public FormattedCommandAlias(String alias, List<String> formatStrings) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         boolean result = false;
         ArrayList<String> commands = new ArrayList<>();
         for (String formatString : formatStrings) {
diff --git a/src/main/java/cn/nukkit/command/PluginCommand.java b/src/main/java/cn/nukkit/command/PluginCommand.java
index 597ecedfb43..e47163e8072 100644
--- a/src/main/java/cn/nukkit/command/PluginCommand.java
+++ b/src/main/java/cn/nukkit/command/PluginCommand.java
@@ -2,6 +2,7 @@
 
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.plugin.Plugin;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * author: MagicDroidX
@@ -21,7 +22,7 @@ public PluginCommand(String name, T owner) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.owningPlugin.isEnabled()) {
             return false;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/BanCommand.java b/src/main/java/cn/nukkit/command/defaults/BanCommand.java
index ca437e55712..4b571523366 100644
--- a/src/main/java/cn/nukkit/command/defaults/BanCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/BanCommand.java
@@ -7,6 +7,7 @@
 import cn.nukkit.command.data.CommandParameter;
 import cn.nukkit.event.player.PlayerKickEvent;
 import cn.nukkit.lang.TranslationContainer;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * author: MagicDroidX
@@ -26,7 +27,7 @@ public BanCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/BanIpCommand.java b/src/main/java/cn/nukkit/command/defaults/BanIpCommand.java
index 7a1b48bb89e..5c9f76abcf0 100644
--- a/src/main/java/cn/nukkit/command/defaults/BanIpCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/BanIpCommand.java
@@ -9,6 +9,7 @@
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.nbt.NBTIO;
 import cn.nukkit.nbt.tag.CompoundTag;
+import org.jetbrains.annotations.NotNull;
 
 import java.io.File;
 import java.io.FileInputStream;
@@ -40,7 +41,7 @@ public BanIpCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/BanListCommand.java b/src/main/java/cn/nukkit/command/defaults/BanListCommand.java
index 0ca654c4e88..1eb5dbce8c2 100644
--- a/src/main/java/cn/nukkit/command/defaults/BanListCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/BanListCommand.java
@@ -6,6 +6,7 @@
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.permission.BanEntry;
 import cn.nukkit.permission.BanList;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.Iterator;
 
@@ -24,7 +25,7 @@ public BanListCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/DebugPasteCommand.java b/src/main/java/cn/nukkit/command/defaults/DebugPasteCommand.java
index 57e765d08bb..77866f8bc78 100644
--- a/src/main/java/cn/nukkit/command/defaults/DebugPasteCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/DebugPasteCommand.java
@@ -9,6 +9,8 @@
 import cn.nukkit.utils.HastebinUtility;
 import cn.nukkit.utils.MainLogger;
 import cn.nukkit.utils.Utils;
+import org.jetbrains.annotations.NotNull;
+
 import java.io.File;
 import java.io.IOException;
 import java.lang.management.ManagementFactory;
@@ -22,7 +24,7 @@ public DebugPasteCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/DefaultGamemodeCommand.java b/src/main/java/cn/nukkit/command/defaults/DefaultGamemodeCommand.java
index 73604ce3cd3..1154b8990ad 100644
--- a/src/main/java/cn/nukkit/command/defaults/DefaultGamemodeCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/DefaultGamemodeCommand.java
@@ -6,6 +6,7 @@
 import cn.nukkit.command.data.CommandParamType;
 import cn.nukkit.command.data.CommandParameter;
 import cn.nukkit.lang.TranslationContainer;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created on 2015/11/12 by xtypr.
@@ -26,7 +27,7 @@ public DefaultGamemodeCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/DeopCommand.java b/src/main/java/cn/nukkit/command/defaults/DeopCommand.java
index 4934da84e69..e1f955d3076 100644
--- a/src/main/java/cn/nukkit/command/defaults/DeopCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/DeopCommand.java
@@ -8,6 +8,7 @@
 import cn.nukkit.command.data.CommandParameter;
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created on 2015/11/12 by xtypr.
@@ -23,7 +24,7 @@ public DeopCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/DifficultyCommand.java b/src/main/java/cn/nukkit/command/defaults/DifficultyCommand.java
index 1b0dcf97a53..55402037726 100644
--- a/src/main/java/cn/nukkit/command/defaults/DifficultyCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/DifficultyCommand.java
@@ -8,6 +8,7 @@
 import cn.nukkit.command.data.CommandParameter;
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.network.protocol.SetDifficultyPacket;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.ArrayList;
 
@@ -30,7 +31,7 @@ public DifficultyCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/EffectCommand.java b/src/main/java/cn/nukkit/command/defaults/EffectCommand.java
index 760db564e36..d1da5077c82 100644
--- a/src/main/java/cn/nukkit/command/defaults/EffectCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/EffectCommand.java
@@ -11,6 +11,7 @@
 import cn.nukkit.potion.InstantEffect;
 import cn.nukkit.utils.ServerException;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 import java.lang.reflect.Field;
 import java.lang.reflect.Modifier;
@@ -48,7 +49,7 @@ public EffectCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/EnchantCommand.java b/src/main/java/cn/nukkit/command/defaults/EnchantCommand.java
index 205e8724d3f..325e9f37c5a 100644
--- a/src/main/java/cn/nukkit/command/defaults/EnchantCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/EnchantCommand.java
@@ -10,6 +10,7 @@
 import cn.nukkit.item.enchantment.Enchantment;
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created by Pub4Game on 23.01.2016.
@@ -38,7 +39,7 @@ public EnchantCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/GamemodeCommand.java b/src/main/java/cn/nukkit/command/defaults/GamemodeCommand.java
index 3f07ae5b1a1..0df6baee0a4 100644
--- a/src/main/java/cn/nukkit/command/defaults/GamemodeCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/GamemodeCommand.java
@@ -9,6 +9,7 @@
 import cn.nukkit.command.data.CommandParameter;
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created on 2015/11/13 by xtypr.
@@ -36,7 +37,7 @@ public GamemodeCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (args.length == 0) {
             sender.sendMessage(new TranslationContainer("commands.generic.usage", this.usageMessage));
             return false;
diff --git a/src/main/java/cn/nukkit/command/defaults/GameruleCommand.java b/src/main/java/cn/nukkit/command/defaults/GameruleCommand.java
index 1015a4cc662..8fd4e6e6160 100644
--- a/src/main/java/cn/nukkit/command/defaults/GameruleCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/GameruleCommand.java
@@ -8,6 +8,7 @@
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.level.GameRule;
 import cn.nukkit.level.GameRules;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -73,7 +74,7 @@ public GameruleCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/GarbageCollectorCommand.java b/src/main/java/cn/nukkit/command/defaults/GarbageCollectorCommand.java
index 94cb5c126c9..c1e8d1526a5 100644
--- a/src/main/java/cn/nukkit/command/defaults/GarbageCollectorCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/GarbageCollectorCommand.java
@@ -4,6 +4,7 @@
 import cn.nukkit.level.Level;
 import cn.nukkit.math.NukkitMath;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created on 2015/11/11 by xtypr.
@@ -18,7 +19,7 @@ public GarbageCollectorCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/GiveCommand.java b/src/main/java/cn/nukkit/command/defaults/GiveCommand.java
index d3cef0469d9..818fcee2129 100644
--- a/src/main/java/cn/nukkit/command/defaults/GiveCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/GiveCommand.java
@@ -9,6 +9,7 @@
 import cn.nukkit.item.Item;
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created on 2015/12/9 by xtypr.
@@ -40,7 +41,7 @@ public GiveCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/HelpCommand.java b/src/main/java/cn/nukkit/command/defaults/HelpCommand.java
index 124c35b46f1..025fc45d4c6 100644
--- a/src/main/java/cn/nukkit/command/defaults/HelpCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/HelpCommand.java
@@ -7,6 +7,7 @@
 import cn.nukkit.command.data.CommandParameter;
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.Map;
 import java.util.TreeMap;
@@ -27,7 +28,7 @@ public HelpCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/KickCommand.java b/src/main/java/cn/nukkit/command/defaults/KickCommand.java
index 1caf85ac982..bc564f3eb83 100644
--- a/src/main/java/cn/nukkit/command/defaults/KickCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/KickCommand.java
@@ -8,6 +8,7 @@
 import cn.nukkit.event.player.PlayerKickEvent;
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created on 2015/11/11 by xtypr.
@@ -26,7 +27,7 @@ public KickCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/KillCommand.java b/src/main/java/cn/nukkit/command/defaults/KillCommand.java
index fcb84d2c710..38e2664595d 100644
--- a/src/main/java/cn/nukkit/command/defaults/KillCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/KillCommand.java
@@ -12,6 +12,7 @@
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.level.Level;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.StringJoiner;
 
@@ -32,7 +33,7 @@ public KillCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/ListCommand.java b/src/main/java/cn/nukkit/command/defaults/ListCommand.java
index 7417211d0c2..abfccdada2d 100644
--- a/src/main/java/cn/nukkit/command/defaults/ListCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/ListCommand.java
@@ -3,6 +3,7 @@
 import cn.nukkit.Player;
 import cn.nukkit.command.CommandSender;
 import cn.nukkit.lang.TranslationContainer;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created on 2015/11/11 by xtypr.
@@ -17,7 +18,7 @@ public ListCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/MeCommand.java b/src/main/java/cn/nukkit/command/defaults/MeCommand.java
index 57a35cfc010..6a0405b3a2a 100644
--- a/src/main/java/cn/nukkit/command/defaults/MeCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/MeCommand.java
@@ -6,6 +6,7 @@
 import cn.nukkit.command.data.CommandParameter;
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created on 2015/11/12 by xtypr.
@@ -23,7 +24,7 @@ public MeCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/OpCommand.java b/src/main/java/cn/nukkit/command/defaults/OpCommand.java
index 6afc9fdcc6c..4ce88c7aa69 100644
--- a/src/main/java/cn/nukkit/command/defaults/OpCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/OpCommand.java
@@ -8,6 +8,7 @@
 import cn.nukkit.command.data.CommandParameter;
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created on 2015/11/12 by xtypr.
@@ -25,7 +26,7 @@ public OpCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/PardonCommand.java b/src/main/java/cn/nukkit/command/defaults/PardonCommand.java
index 0ffd5296b72..f0d97880a83 100644
--- a/src/main/java/cn/nukkit/command/defaults/PardonCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/PardonCommand.java
@@ -5,6 +5,7 @@
 import cn.nukkit.command.data.CommandParamType;
 import cn.nukkit.command.data.CommandParameter;
 import cn.nukkit.lang.TranslationContainer;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * author: MagicDroidX
@@ -23,7 +24,7 @@ public PardonCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/PardonIpCommand.java b/src/main/java/cn/nukkit/command/defaults/PardonIpCommand.java
index d3ae0695a85..4ae4cbf0694 100644
--- a/src/main/java/cn/nukkit/command/defaults/PardonIpCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/PardonIpCommand.java
@@ -5,6 +5,7 @@
 import cn.nukkit.command.data.CommandParamType;
 import cn.nukkit.command.data.CommandParameter;
 import cn.nukkit.lang.TranslationContainer;
+import org.jetbrains.annotations.NotNull;
 
 import java.net.InetAddress;
 import java.net.UnknownHostException;
@@ -27,7 +28,7 @@ public PardonIpCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/ParticleCommand.java b/src/main/java/cn/nukkit/command/defaults/ParticleCommand.java
index aea1e78c51e..8a49273cfd7 100644
--- a/src/main/java/cn/nukkit/command/defaults/ParticleCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/ParticleCommand.java
@@ -11,6 +11,7 @@
 import cn.nukkit.level.Position;
 import cn.nukkit.level.particle.*;
 import cn.nukkit.math.Vector3;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.Random;
 import java.util.concurrent.ThreadLocalRandom;
@@ -37,7 +38,7 @@ public ParticleCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/PluginsCommand.java b/src/main/java/cn/nukkit/command/defaults/PluginsCommand.java
index b3377bfd251..12fc3edafe1 100644
--- a/src/main/java/cn/nukkit/command/defaults/PluginsCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/PluginsCommand.java
@@ -4,6 +4,7 @@
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.plugin.Plugin;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.Map;
 
@@ -24,7 +25,7 @@ public PluginsCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/ReloadCommand.java b/src/main/java/cn/nukkit/command/defaults/ReloadCommand.java
index 718c140b5b5..0f95ab5a03e 100644
--- a/src/main/java/cn/nukkit/command/defaults/ReloadCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/ReloadCommand.java
@@ -4,6 +4,7 @@
 import cn.nukkit.command.CommandSender;
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * author: MagicDroidX
@@ -18,7 +19,7 @@ public ReloadCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/SaveCommand.java b/src/main/java/cn/nukkit/command/defaults/SaveCommand.java
index 9e119f2d104..f84169a5556 100644
--- a/src/main/java/cn/nukkit/command/defaults/SaveCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/SaveCommand.java
@@ -5,6 +5,7 @@
 import cn.nukkit.command.CommandSender;
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.level.Level;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created on 2015/11/13 by xtypr.
@@ -19,7 +20,7 @@ public SaveCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/SaveOffCommand.java b/src/main/java/cn/nukkit/command/defaults/SaveOffCommand.java
index 762cd3140bb..f6e0cb22ebc 100644
--- a/src/main/java/cn/nukkit/command/defaults/SaveOffCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/SaveOffCommand.java
@@ -3,6 +3,7 @@
 import cn.nukkit.command.Command;
 import cn.nukkit.command.CommandSender;
 import cn.nukkit.lang.TranslationContainer;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created on 2015/11/13 by xtypr.
@@ -17,7 +18,7 @@ public SaveOffCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/SaveOnCommand.java b/src/main/java/cn/nukkit/command/defaults/SaveOnCommand.java
index a3f6a5dfdd3..0e050550ccc 100644
--- a/src/main/java/cn/nukkit/command/defaults/SaveOnCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/SaveOnCommand.java
@@ -3,6 +3,7 @@
 import cn.nukkit.command.Command;
 import cn.nukkit.command.CommandSender;
 import cn.nukkit.lang.TranslationContainer;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created on 2015/11/13 by xtypr.
@@ -17,7 +18,7 @@ public SaveOnCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/SayCommand.java b/src/main/java/cn/nukkit/command/defaults/SayCommand.java
index a55d3c459cf..fb9308d33fc 100644
--- a/src/main/java/cn/nukkit/command/defaults/SayCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/SayCommand.java
@@ -7,6 +7,7 @@
 import cn.nukkit.command.data.CommandParameter;
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created on 2015/11/12 by xtypr.
@@ -24,7 +25,7 @@ public SayCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/SeedCommand.java b/src/main/java/cn/nukkit/command/defaults/SeedCommand.java
index 3c70e7dd5f1..00ef0fe2b17 100644
--- a/src/main/java/cn/nukkit/command/defaults/SeedCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/SeedCommand.java
@@ -3,6 +3,7 @@
 import cn.nukkit.Player;
 import cn.nukkit.command.CommandSender;
 import cn.nukkit.lang.TranslationContainer;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * author: MagicDroidX
@@ -17,7 +18,7 @@ public SeedCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/SetWorldSpawnCommand.java b/src/main/java/cn/nukkit/command/defaults/SetWorldSpawnCommand.java
index fcb93688eb2..0f2735d90c2 100644
--- a/src/main/java/cn/nukkit/command/defaults/SetWorldSpawnCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/SetWorldSpawnCommand.java
@@ -8,6 +8,7 @@
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.level.Level;
 import cn.nukkit.math.Vector3;
+import org.jetbrains.annotations.NotNull;
 
 import java.text.DecimalFormat;
 
@@ -26,7 +27,7 @@ public SetWorldSpawnCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/SpawnpointCommand.java b/src/main/java/cn/nukkit/command/defaults/SpawnpointCommand.java
index bf10543d072..9d9a8c85b87 100644
--- a/src/main/java/cn/nukkit/command/defaults/SpawnpointCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/SpawnpointCommand.java
@@ -9,6 +9,7 @@
 import cn.nukkit.level.Level;
 import cn.nukkit.level.Position;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 import java.text.DecimalFormat;
 
@@ -28,7 +29,7 @@ public SpawnpointCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/StatusCommand.java b/src/main/java/cn/nukkit/command/defaults/StatusCommand.java
index ac1e3ca13a6..09a47320857 100644
--- a/src/main/java/cn/nukkit/command/defaults/StatusCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/StatusCommand.java
@@ -6,6 +6,7 @@
 import cn.nukkit.level.Level;
 import cn.nukkit.math.NukkitMath;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.Objects;
 import java.util.concurrent.TimeUnit;
@@ -27,7 +28,7 @@ public StatusCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/StopCommand.java b/src/main/java/cn/nukkit/command/defaults/StopCommand.java
index 0c89133e00f..d934026606f 100644
--- a/src/main/java/cn/nukkit/command/defaults/StopCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/StopCommand.java
@@ -3,6 +3,7 @@
 import cn.nukkit.command.Command;
 import cn.nukkit.command.CommandSender;
 import cn.nukkit.lang.TranslationContainer;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * author: MagicDroidX
@@ -17,7 +18,7 @@ public StopCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/TeleportCommand.java b/src/main/java/cn/nukkit/command/defaults/TeleportCommand.java
index e69aa948808..7813f845373 100644
--- a/src/main/java/cn/nukkit/command/defaults/TeleportCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/TeleportCommand.java
@@ -10,6 +10,7 @@
 import cn.nukkit.level.Location;
 import cn.nukkit.math.NukkitMath;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created on 2015/11/12 by Pub4Game and milkice.
@@ -41,7 +42,7 @@ public TeleportCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/TellCommand.java b/src/main/java/cn/nukkit/command/defaults/TellCommand.java
index 37dc1426bd7..dddc44108e7 100644
--- a/src/main/java/cn/nukkit/command/defaults/TellCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/TellCommand.java
@@ -6,6 +6,7 @@
 import cn.nukkit.command.data.CommandParameter;
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.Objects;
 
@@ -26,7 +27,7 @@ public TellCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/TimeCommand.java b/src/main/java/cn/nukkit/command/defaults/TimeCommand.java
index 5d6f39ad95d..401db23621f 100644
--- a/src/main/java/cn/nukkit/command/defaults/TimeCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/TimeCommand.java
@@ -9,6 +9,7 @@
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.level.Level;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created on 2015/11/11 by xtypr.
@@ -41,7 +42,7 @@ public TimeCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (args.length < 1) {
             sender.sendMessage(new TranslationContainer("commands.generic.usage", this.usageMessage));
 
diff --git a/src/main/java/cn/nukkit/command/defaults/TimingsCommand.java b/src/main/java/cn/nukkit/command/defaults/TimingsCommand.java
index beb9354e2ba..3d83305f42b 100644
--- a/src/main/java/cn/nukkit/command/defaults/TimingsCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/TimingsCommand.java
@@ -6,6 +6,7 @@
 import cn.nukkit.lang.TranslationContainer;
 import co.aikar.timings.Timings;
 import co.aikar.timings.TimingsExport;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * @author fromgate
@@ -23,7 +24,7 @@ public TimingsCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/TitleCommand.java b/src/main/java/cn/nukkit/command/defaults/TitleCommand.java
index 2bdf150c741..744cfe320ef 100644
--- a/src/main/java/cn/nukkit/command/defaults/TitleCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/TitleCommand.java
@@ -8,6 +8,7 @@
 import cn.nukkit.command.data.CommandParameter;
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * @author Tee7even
@@ -41,7 +42,7 @@ public TitleCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/VersionCommand.java b/src/main/java/cn/nukkit/command/defaults/VersionCommand.java
index 0fbfe8a6949..6e818ea6165 100644
--- a/src/main/java/cn/nukkit/command/defaults/VersionCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/VersionCommand.java
@@ -8,6 +8,7 @@
 import cn.nukkit.plugin.Plugin;
 import cn.nukkit.plugin.PluginDescription;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.List;
 
@@ -31,7 +32,7 @@ public VersionCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/WeatherCommand.java b/src/main/java/cn/nukkit/command/defaults/WeatherCommand.java
index f85de3c6d19..9c0ba068cf6 100644
--- a/src/main/java/cn/nukkit/command/defaults/WeatherCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/WeatherCommand.java
@@ -8,6 +8,7 @@
 import cn.nukkit.command.data.CommandParameter;
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.level.Level;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * author: Angelic47
@@ -26,7 +27,7 @@ public WeatherCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/WhitelistCommand.java b/src/main/java/cn/nukkit/command/defaults/WhitelistCommand.java
index 39b3a487e21..f3024f0aab4 100644
--- a/src/main/java/cn/nukkit/command/defaults/WhitelistCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/WhitelistCommand.java
@@ -7,6 +7,7 @@
 import cn.nukkit.command.data.CommandParameter;
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created on 2015/11/12 by xtypr.
@@ -35,7 +36,7 @@ public WhitelistCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/defaults/XpCommand.java b/src/main/java/cn/nukkit/command/defaults/XpCommand.java
index 26a5a5f9323..a0aaafaccb1 100644
--- a/src/main/java/cn/nukkit/command/defaults/XpCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/XpCommand.java
@@ -7,6 +7,7 @@
 import cn.nukkit.command.data.CommandParameter;
 import cn.nukkit.lang.TranslationContainer;
 import cn.nukkit.utils.TextFormat;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Created by Snake1999 on 2016/1/22.
@@ -28,7 +29,7 @@ public XpCommand(String name) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (!this.testPermission(sender)) {
             return true;
         }
diff --git a/src/main/java/cn/nukkit/command/simple/SimpleCommand.java b/src/main/java/cn/nukkit/command/simple/SimpleCommand.java
index 6fae8ab119f..92079242ba3 100644
--- a/src/main/java/cn/nukkit/command/simple/SimpleCommand.java
+++ b/src/main/java/cn/nukkit/command/simple/SimpleCommand.java
@@ -5,6 +5,7 @@
 import cn.nukkit.command.CommandSender;
 import cn.nukkit.command.ConsoleCommandSender;
 import cn.nukkit.lang.TranslationContainer;
+import org.jetbrains.annotations.NotNull;
 
 import java.lang.reflect.Method;
 
@@ -47,7 +48,7 @@ public void sendInGameMessage(CommandSender sender) {
     }
 
     @Override
-    public boolean execute(CommandSender sender, String commandLabel, String[] args) {
+    public boolean execute(@NotNull CommandSender sender, String commandLabel, String[] args) {
         if (this.forbidConsole && sender instanceof ConsoleCommandSender) {
             this.sendInGameMessage(sender);
             return false;