SPIGOT-2540: Add nullability annotations to entire Bukkit API

By: Darkyenus <darkyenus@gmail.com>

paper-api/src/main/java/org/bukkit/command/CommandSender.java

@@ -2,6 +2,7 @@ package org.bukkit.command;
 
 import org.bukkit.Server;
 import org.bukkit.permissions.Permissible;
+import org.jetbrains.annotations.NotNull;
 
 public interface CommandSender extends Permissible {
 
@@ -10,20 +11,21 @@ public interface CommandSender extends Permissible {
      *
      * @param message Message to be displayed
      */
-    public void sendMessage(String message);
+    public void sendMessage(@NotNull String message);
 
     /**
      * Sends this sender multiple messages
      *
      * @param messages An array of messages to be displayed
      */
-    public void sendMessage(String[] messages);
+    public void sendMessage(@NotNull String[] messages);
 
     /**
      * Returns the server instance that this command is running on
      *
      * @return Server instance
      */
+    @NotNull
     public Server getServer();
 
     /**
@@ -31,5 +33,6 @@ public interface CommandSender extends Permissible {
      *
      * @return Name of the sender
      */
+    @NotNull
     public String getName();
 }