diff --git a/src/main/java/fr/themode/demo/commands/EntitySelectorCommand.java b/src/main/java/fr/themode/demo/commands/EntitySelectorCommand.java
index 1af4b5168..be4c52878 100644
--- a/src/main/java/fr/themode/demo/commands/EntitySelectorCommand.java
+++ b/src/main/java/fr/themode/demo/commands/EntitySelectorCommand.java
@@ -7,7 +7,7 @@ import net.minestom.server.command.builder.arguments.ArgumentType;
 import net.minestom.server.command.builder.arguments.minecraft.ArgumentEntities;
 import net.minestom.server.entity.Entity;
 
-import java.util.ArrayList;
+import java.util.List;
 
 public class EntitySelectorCommand extends Command {
 
@@ -21,6 +21,6 @@ public class EntitySelectorCommand extends Command {
     }
 
     private void executor(CommandSender commandSender, Arguments arguments) {
-        ArrayList<Entity> entities = arguments.getEntities("entities");
+        List<Entity> entities = arguments.getEntities("entities");
     }
 }
diff --git a/src/main/java/net/minestom/server/command/CommandManager.java b/src/main/java/net/minestom/server/command/CommandManager.java
index adcc9eca4..4b9e4290e 100644
--- a/src/main/java/net/minestom/server/command/CommandManager.java
+++ b/src/main/java/net/minestom/server/command/CommandManager.java
@@ -378,7 +378,7 @@ public class CommandManager {
         return literalNode;
     }
 
-    private List<DeclareCommandsPacket.Node> toNodes(Argument argument, boolean executable) {
+    private List<DeclareCommandsPacket.Node> toNodes(Argument<?> argument, boolean executable) {
         List<DeclareCommandsPacket.Node> nodes = new ArrayList<>();
 
         /*DeclareCommandsPacket.Node testNode = simpleArgumentNode(nodes, argument, executable);
@@ -515,7 +515,7 @@ public class CommandManager {
         return nodes;
     }
 
-    private byte getNumberProperties(ArgumentNumber argumentNumber) {
+    private byte getNumberProperties(ArgumentNumber<? extends Number> argumentNumber) {
         byte result = 0;
         if (argumentNumber.hasMin())
             result += 1;
@@ -525,7 +525,7 @@ public class CommandManager {
     }
 
     private DeclareCommandsPacket.Node simpleArgumentNode(List<DeclareCommandsPacket.Node> nodes,
-                                                          Argument argument, boolean executable) {
+                                                          Argument<?> argument, boolean executable) {
         DeclareCommandsPacket.Node argumentNode = new DeclareCommandsPacket.Node();
         nodes.add(argumentNode);
 
diff --git a/src/main/java/net/minestom/server/command/builder/Arguments.java b/src/main/java/net/minestom/server/command/builder/Arguments.java
index edbf9a030..2f8fa2021 100644
--- a/src/main/java/net/minestom/server/command/builder/Arguments.java
+++ b/src/main/java/net/minestom/server/command/builder/Arguments.java
@@ -11,13 +11,13 @@ import net.minestom.server.utils.math.FloatRange;
 import net.minestom.server.utils.math.IntRange;
 import net.minestom.server.utils.time.UpdateOption;
 
-import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 public class Arguments {
 
-    private Map<String, Object> args = new HashMap<>();
+    private final Map<String, Object> args = new HashMap<>();
 
     public Structure getStructure(String id) {
         return (Structure) getObject(id);
@@ -87,8 +87,8 @@ public class Arguments {
         return (FloatRange) getObject(id);
     }
 
-    public ArrayList<Entity> getEntities(String id) {
-        return (ArrayList<Entity>) getObject(id);
+    public List<Entity> getEntities(String id) {
+        return (List<Entity>) getObject(id);
     }
 
     public Object getObject(String id) {
diff --git a/src/main/java/net/minestom/server/command/builder/arguments/minecraft/ArgumentTime.java b/src/main/java/net/minestom/server/command/builder/arguments/minecraft/ArgumentTime.java
index bf6ea7bcc..cb43caa29 100644
--- a/src/main/java/net/minestom/server/command/builder/arguments/minecraft/ArgumentTime.java
+++ b/src/main/java/net/minestom/server/command/builder/arguments/minecraft/ArgumentTime.java
@@ -29,7 +29,7 @@ public class ArgumentTime extends Argument<UpdateOption> {
         value = value.substring(0, value.length() - 1);
         try {
             // Check if value is a number
-            Integer.valueOf(value);
+            Integer.parseInt(value);
 
             return SUCCESS;
         } catch (NumberFormatException e) {
@@ -49,7 +49,7 @@ public class ArgumentTime extends Argument<UpdateOption> {
             timeUnit = TimeUnit.TICK;
         }
         value = value.substring(0, value.length() - 1);
-        final int time = Integer.valueOf(value);
+        final int time = Integer.parseInt(value);
 
         return new UpdateOption(time, timeUnit);
     }
diff --git a/src/main/java/net/minestom/server/command/builder/arguments/number/ArgumentNumber.java b/src/main/java/net/minestom/server/command/builder/arguments/number/ArgumentNumber.java
index 89572bf68..4c572ff1b 100644
--- a/src/main/java/net/minestom/server/command/builder/arguments/number/ArgumentNumber.java
+++ b/src/main/java/net/minestom/server/command/builder/arguments/number/ArgumentNumber.java
@@ -5,7 +5,7 @@ import net.minestom.server.command.builder.arguments.Argument;
 import java.math.BigDecimal;
 import java.util.regex.Pattern;
 
-public abstract class ArgumentNumber<T> extends Argument<T> {
+public abstract class ArgumentNumber<T extends Number> extends Argument<T> {
 
     public static final int NOT_NUMBER_ERROR = 1;
     public static final int RANGE_ERROR = 2;
@@ -17,19 +17,19 @@ public abstract class ArgumentNumber<T> extends Argument<T> {
         super(id, false);
     }
 
-    public ArgumentNumber min(T value) {
+    public ArgumentNumber<T> min(T value) {
         this.min = value;
         this.hasMin = true;
         return this;
     }
 
-    public ArgumentNumber max(T value) {
+    public ArgumentNumber<T> max(T value) {
         this.max = value;
         this.hasMax = true;
         return this;
     }
 
-    public ArgumentNumber between(T min, T max) {
+    public ArgumentNumber<T> between(T min, T max) {
         this.min = min;
         this.max = max;
         this.hasMin = true;