diff --git a/README.md b/README.md
index 6ca5554..2e9ec56 100644
--- a/README.md
+++ b/README.md
@@ -23,10 +23,11 @@ permission permanently by another cause) when they expire.
 
 ### The create command
 
-/ps create \<name> \<description> \<permission,permission> \<cost> \<duration> - Creates a new permission sign. The name is
+/ps create \<name> \<description> \<permission,permission> \<cost> \<duration> - Creates a new permission sign. The name
+is
 used to describe what the permission sign does, and is displayed on the sign. The description is used to describe what
 the permission sign does, but without any limit on the length (use "_" between words, like: This_is_a_sentence). To use
-actual underscores, escape them like "\\_". The permission,permission is the list of comma-separated permissions the
+actual underscores, escape them like "\_". The permission,permission is the list of comma-separated permissions the
 permission sign will grant to the using player. The cost is the cost to use the permission sign. The duration is the
 number of seconds the player should keep the permission for. Use 0 for permanent.
 
diff --git a/pom.xml b/pom.xml
index 1919568..04a2601 100644
--- a/pom.xml
+++ b/pom.xml
@@ -6,7 +6,7 @@
 
     <groupId>net.knarcraft</groupId>
     <artifactId>PermissionSigns</artifactId>
-    <version>1.0.5-SNAPSHOT</version>
+    <version>1.0.5</version>
     <packaging>jar</packaging>
 
     <name>PermissionSigns</name>
@@ -73,7 +73,7 @@
         <dependency>
             <groupId>org.spigotmc</groupId>
             <artifactId>spigot-api</artifactId>
-            <version>1.20.1-R0.1-SNAPSHOT</version>
+            <version>1.20.4-R0.1-SNAPSHOT</version>
             <scope>provided</scope>
         </dependency>
         <dependency>
@@ -88,5 +88,11 @@
             <version>1.7</version>
             <scope>provided</scope>
         </dependency>
+        <dependency>
+            <groupId>net.knarcraft</groupId>
+            <artifactId>knarlib</artifactId>
+            <version>1.2.4</version>
+            <scope>compile</scope>
+        </dependency>
     </dependencies>
 </project>
diff --git a/src/main/java/net/knarcraft/permissionsigns/command/AboutCommand.java b/src/main/java/net/knarcraft/permissionsigns/command/AboutCommand.java
index d418364..bab3f5e 100644
--- a/src/main/java/net/knarcraft/permissionsigns/command/AboutCommand.java
+++ b/src/main/java/net/knarcraft/permissionsigns/command/AboutCommand.java
@@ -14,7 +14,8 @@ import org.jetbrains.annotations.NotNull;
 public class AboutCommand implements CommandExecutor {
 
     @Override
-    public boolean onCommand(CommandSender sender, @NotNull Command command, @NotNull String label, @NotNull String[] args) {
+    public boolean onCommand(CommandSender sender, @NotNull Command command, @NotNull String label,
+                             @NotNull String[] args) {
         sender.sendMessage(StringFormatter.formatInfoMessage("Permission Signs plugin created by " + ChatColor.GOLD +
                 "EpicKnarvik97"));
         sender.sendMessage(StringFormatter.formatInfoMessage("Plugin version: " + PermissionSigns.getPluginVersion()));
diff --git a/src/main/java/net/knarcraft/permissionsigns/command/CancelCommand.java b/src/main/java/net/knarcraft/permissionsigns/command/CancelCommand.java
index 22126d6..18ab990 100644
--- a/src/main/java/net/knarcraft/permissionsigns/command/CancelCommand.java
+++ b/src/main/java/net/knarcraft/permissionsigns/command/CancelCommand.java
@@ -15,7 +15,8 @@ import org.jetbrains.annotations.NotNull;
 public class CancelCommand implements CommandExecutor {
 
     @Override
-    public boolean onCommand(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label, @NotNull String[] args) {
+    public boolean onCommand(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label,
+                             @NotNull String[] args) {
         if (sender instanceof Player player) {
             if (sender.hasPermission("permissionsigns.admin.create")) {
                 PermissionSigns.cancelSignCreationRequest(player.getUniqueId());
diff --git a/src/main/java/net/knarcraft/permissionsigns/command/CreateCommand.java b/src/main/java/net/knarcraft/permissionsigns/command/CreateCommand.java
index 60b7710..63f7c1c 100644
--- a/src/main/java/net/knarcraft/permissionsigns/command/CreateCommand.java
+++ b/src/main/java/net/knarcraft/permissionsigns/command/CreateCommand.java
@@ -19,10 +19,12 @@ import java.util.List;
 public class CreateCommand implements CommandExecutor {
 
     @Override
-    public boolean onCommand(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label, @NotNull String[] args) {
+    public boolean onCommand(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label,
+                             @NotNull String[] args) {
         // /ps create <name> <permission,permission> <cost> <duration> to create a new permission-sign
         //Name and permission(s) required, but duration and cost optional
-        String usage = "/ps create <name> <description> <permission,permission> [cost] [duration] - Used for creating a new permission sign";
+        String usage = "/ps create <name> <description> <permission,permission> [cost] [duration] - Used for creating" +
+                " a new permission sign";
         if (!(sender instanceof Player)) {
             sender.sendMessage(StringFormatter.getTranslatedErrorMessage(TranslatableMessage.COMMAND_PLAYER_ONLY));
             return false;
@@ -101,7 +103,7 @@ public class CreateCommand implements CommandExecutor {
      * @param description <p>The description to replace underscores in</p>
      * @return <p>The string with underscores replaced</p>
      */
-    private String replaceUnderscoresWithSpaces(String description) {
+    private @NotNull String replaceUnderscoresWithSpaces(@NotNull String description) {
         String temporaryString = "\\|ESCAPED-UNDERSCORE\\|";
         description = description.replaceAll("\\\\_", temporaryString);
         description = description.replaceAll("_", " ");
diff --git a/src/main/java/net/knarcraft/permissionsigns/command/CreateTabCompleter.java b/src/main/java/net/knarcraft/permissionsigns/command/CreateTabCompleter.java
index 2b70378..1185c9d 100644
--- a/src/main/java/net/knarcraft/permissionsigns/command/CreateTabCompleter.java
+++ b/src/main/java/net/knarcraft/permissionsigns/command/CreateTabCompleter.java
@@ -61,7 +61,7 @@ public class CreateTabCompleter implements TabCompleter {
      * @param typedNode <p>The full permission node typed by the player</p>
      * @return <p>All known valid auto-complete options</p>
      */
-    private List<String> tabCompletePermission(String typedNode) {
+    private @NotNull List<String> tabCompletePermission(@NotNull String typedNode) {
         StringBuilder permissionListString = new StringBuilder();
         if (typedNode.contains(",")) {
             String[] permissionList = typedNode.split(",");
@@ -110,7 +110,7 @@ public class CreateTabCompleter implements TabCompleter {
      * @param typedText <p>The text the player has started typing</p>
      * @return <p>The given string values which start with the player's typed text</p>
      */
-    private List<String> filterMatching(List<String> values, String typedText) {
+    private @NotNull List<String> filterMatching(@NotNull List<String> values, @NotNull String typedText) {
         List<String> configValues = new ArrayList<>();
         for (String value : values) {
             if (value.toLowerCase().startsWith(typedText.toLowerCase())) {
@@ -137,7 +137,7 @@ public class CreateTabCompleter implements TabCompleter {
      *
      * @param permissionName <p>The permission to load</p>
      */
-    private static void loadPermission(String permissionName) {
+    private static void loadPermission(@NotNull String permissionName) {
         String[] permissionParts = permissionName.split("\\.");
         if (permissionParts.length == 1 && !plugins.contains(permissionParts[0])) {
             plugins.add(permissionParts[0]);
diff --git a/src/main/java/net/knarcraft/permissionsigns/command/PermissionSignsCommand.java b/src/main/java/net/knarcraft/permissionsigns/command/PermissionSignsCommand.java
index 9a54fe5..d59fde3 100644
--- a/src/main/java/net/knarcraft/permissionsigns/command/PermissionSignsCommand.java
+++ b/src/main/java/net/knarcraft/permissionsigns/command/PermissionSignsCommand.java
@@ -13,7 +13,8 @@ import java.util.Arrays;
 public class PermissionSignsCommand implements CommandExecutor {
 
     @Override
-    public boolean onCommand(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label, String[] args) {
+    public boolean onCommand(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label,
+                             @NotNull String[] args) {
         if (args.length > 0) {
             if (args[0].equalsIgnoreCase("create")) {
                 String[] subArgs = Arrays.copyOfRange(args, 1, args.length);
diff --git a/src/main/java/net/knarcraft/permissionsigns/command/PermissionSignsTabCompleter.java b/src/main/java/net/knarcraft/permissionsigns/command/PermissionSignsTabCompleter.java
index a0661aa..317c778 100644
--- a/src/main/java/net/knarcraft/permissionsigns/command/PermissionSignsTabCompleter.java
+++ b/src/main/java/net/knarcraft/permissionsigns/command/PermissionSignsTabCompleter.java
@@ -16,7 +16,8 @@ import java.util.List;
 public class PermissionSignsTabCompleter implements TabCompleter {
 
     @Override
-    public List<String> onTabComplete(@NotNull CommandSender sender, @NotNull Command command, @NotNull String alias, @NotNull String[] args) {
+    public List<String> onTabComplete(@NotNull CommandSender sender, @NotNull Command command, @NotNull String alias,
+                                      @NotNull String[] args) {
         if (args.length == 1) {
             List<String> commands = getAvailableCommands(sender);
             List<String> matchingCommands = new ArrayList<>();
@@ -40,7 +41,7 @@ public class PermissionSignsTabCompleter implements TabCompleter {
      * @param commandSender <p>The command sender to get available commands for</p>
      * @return <p>The commands available to the command sender</p>
      */
-    private List<String> getAvailableCommands(CommandSender commandSender) {
+    private List<String> getAvailableCommands(@NotNull CommandSender commandSender) {
         List<String> commands = new ArrayList<>();
         commands.add("about");
         if (!(commandSender instanceof Player player) || player.hasPermission("permissionsigns.admin.reload")) {
diff --git a/src/main/java/net/knarcraft/permissionsigns/command/ReloadCommand.java b/src/main/java/net/knarcraft/permissionsigns/command/ReloadCommand.java
index 2c197a3..796fb94 100644
--- a/src/main/java/net/knarcraft/permissionsigns/command/ReloadCommand.java
+++ b/src/main/java/net/knarcraft/permissionsigns/command/ReloadCommand.java
@@ -16,7 +16,8 @@ import org.jetbrains.annotations.NotNull;
 public class ReloadCommand implements CommandExecutor {
 
     @Override
-    public boolean onCommand(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label, @NotNull String[] args) {
+    public boolean onCommand(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label,
+                             @NotNull String[] args) {
         if (sender.hasPermission("permissionsigns.admin.reload")) {
             SignManager.loadSigns();
             PermissionManager.loadTemporaryPermissions();
diff --git a/src/main/java/net/knarcraft/permissionsigns/container/PermissionSign.java b/src/main/java/net/knarcraft/permissionsigns/container/PermissionSign.java
index 0e9bdd6..bc4d316 100644
--- a/src/main/java/net/knarcraft/permissionsigns/container/PermissionSign.java
+++ b/src/main/java/net/knarcraft/permissionsigns/container/PermissionSign.java
@@ -4,6 +4,8 @@ import net.knarcraft.permissionsigns.formatting.TranslatableMessage;
 import net.knarcraft.permissionsigns.formatting.Translator;
 import net.knarcraft.permissionsigns.manager.EconomyManager;
 import org.bukkit.Location;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
 import java.util.Collections;
@@ -38,8 +40,8 @@ public class PermissionSign {
      * @param duration        <p>The duration, in seconds, until the permission should be revoked. 0 for non-temporary</p>
      * @param cost            <p>The cost of using this permission sign</p>
      */
-    public PermissionSign(Location signLocation, String name, String description, List<String> permissionNodes,
-                          int duration, double cost) {
+    public PermissionSign(@NotNull Location signLocation, @NotNull String name, @NotNull String description,
+                          @NotNull List<String> permissionNodes, int duration, double cost) {
         this.signLocation = signLocation;
         this.name = name;
         this.description = description;
@@ -59,7 +61,8 @@ public class PermissionSign {
      * @param duration        <p>The duration, in seconds, until the permission should be revoked. 0 for non-temporary</p>
      * @param cost            <p>The cost of using this permission sign</p>
      */
-    public PermissionSign(String name, String description, List<String> permissionNodes, int duration, double cost) {
+    public PermissionSign(@NotNull String name, @NotNull String description, @NotNull List<String> permissionNodes,
+                          int duration, double cost) {
         this.name = name;
         this.description = description;
         this.permissionNodes = new ArrayList<>(permissionNodes);
@@ -72,7 +75,7 @@ public class PermissionSign {
      *
      * @param signLocation <p>>The location of this permission sign's actual sign</p>
      */
-    public void setSignLocation(Location signLocation) {
+    public void setSignLocation(@NotNull Location signLocation) {
         if (this.signLocation == null) {
             this.signLocation = signLocation;
         } else {
@@ -87,7 +90,7 @@ public class PermissionSign {
      *
      * @return <p>The location of this permission sign</p>
      */
-    public Location getSignLocation() {
+    public @NotNull Location getSignLocation() {
         return signLocation;
     }
 
@@ -96,7 +99,7 @@ public class PermissionSign {
      *
      * @return <p>The name of this permission sign</p>
      */
-    public String getName() {
+    public @NotNull String getName() {
         return name;
     }
 
@@ -105,7 +108,7 @@ public class PermissionSign {
      *
      * @return <p>The description of this permission sign</p>
      */
-    public String getDescription() {
+    public @NotNull String getDescription() {
         return description;
     }
 
@@ -114,7 +117,7 @@ public class PermissionSign {
      *
      * @return <p>The permission nodes granted by this permission sign</p>
      */
-    public List<String> getPermissionNodes() {
+    public @NotNull List<String> getPermissionNodes() {
         return new ArrayList<>(this.permissionNodes);
     }
 
@@ -143,7 +146,7 @@ public class PermissionSign {
      *
      * @return <p>The lines used to draw this permission sign</p>
      */
-    public String[] getSignLines() {
+    public @NotNull String[] getSignLines() {
         String[] lines = new String[4];
         lines[0] = Translator.getTranslatedMessage(TranslatableMessage.SIGN_PREFIX);
         lines[1] = replacePlaceholder(Translator.getTranslatedMessage(
@@ -154,7 +157,7 @@ public class PermissionSign {
     }
 
     @Override
-    public boolean equals(Object other) {
+    public boolean equals(@Nullable Object other) {
         if (!(other instanceof PermissionSign)) {
             return false;
         }
@@ -170,7 +173,7 @@ public class PermissionSign {
      *
      * @return <p>The string used for displaying this sign's duration</p>
      */
-    public String getDurationString() {
+    public @NotNull String getDurationString() {
         if (duration == 0) {
             return Translator.getTranslatedMessage(TranslatableMessage.SIGN_PERMANENT);
         } else {
@@ -193,7 +196,7 @@ public class PermissionSign {
      *
      * @return <p>The string used for displaying this sign's cost</p>
      */
-    public String getCostString() {
+    public @NotNull String getCostString() {
         if (cost == 0) {
             return Translator.getTranslatedMessage(TranslatableMessage.SIGN_COST_FREE);
         } else {
@@ -219,7 +222,8 @@ public class PermissionSign {
      * @param castToInt           <p>Whether to cast the duration to an int</p>
      * @return <p>The formatted duration string</p>
      */
-    private String formatDurationString(double duration, TranslatableMessage translatableMessage, boolean castToInt) {
+    private @NotNull String formatDurationString(double duration, @NotNull TranslatableMessage translatableMessage,
+                                                 boolean castToInt) {
         String durationFormat = Translator.getTranslatedMessage(TranslatableMessage.SIGN_DURATION_FORMAT);
         durationFormat = replacePlaceholder(durationFormat, "{unit}",
                 Translator.getTranslatedMessage(translatableMessage));
diff --git a/src/main/java/net/knarcraft/permissionsigns/container/SignCreationRequest.java b/src/main/java/net/knarcraft/permissionsigns/container/SignCreationRequest.java
index be225ca..8fdf464 100644
--- a/src/main/java/net/knarcraft/permissionsigns/container/SignCreationRequest.java
+++ b/src/main/java/net/knarcraft/permissionsigns/container/SignCreationRequest.java
@@ -1,6 +1,8 @@
 package net.knarcraft.permissionsigns.container;
 
 import org.bukkit.entity.Player;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 /**
  * A sign creation request represents the state where a player has used the create command, but not clicked a sign
@@ -18,7 +20,7 @@ public class SignCreationRequest implements Comparable<SignCreationRequest> {
      * @param player         <p>The player starting to create the permission sign</p>
      * @param initiationTime <p>The time the request was initiated</p>
      */
-    public SignCreationRequest(PermissionSign permissionSign, Player player, long initiationTime) {
+    public SignCreationRequest(@NotNull PermissionSign permissionSign, @NotNull Player player, long initiationTime) {
         this.permissionSign = permissionSign;
         this.player = player;
         this.initiationTime = initiationTime;
@@ -29,7 +31,7 @@ public class SignCreationRequest implements Comparable<SignCreationRequest> {
      *
      * @return <p>The involved permission sign</p>
      */
-    public PermissionSign getPermissionSign() {
+    public @NotNull PermissionSign getPermissionSign() {
         return this.permissionSign;
     }
 
@@ -38,7 +40,7 @@ public class SignCreationRequest implements Comparable<SignCreationRequest> {
      *
      * @return <p>The involved player</p>
      */
-    public Player getPlayer() {
+    public @NotNull Player getPlayer() {
         return this.player;
     }
 
@@ -52,7 +54,7 @@ public class SignCreationRequest implements Comparable<SignCreationRequest> {
     }
 
     @Override
-    public boolean equals(Object other) {
+    public boolean equals(@Nullable Object other) {
         if (!(other instanceof SignCreationRequest otherRequest)) {
             return false;
         }
@@ -64,7 +66,7 @@ public class SignCreationRequest implements Comparable<SignCreationRequest> {
     }
 
     @Override
-    public int compareTo(SignCreationRequest other) {
+    public int compareTo(@NotNull SignCreationRequest other) {
         return (int) (this.initiationTime - other.initiationTime);
     }
 }
diff --git a/src/main/java/net/knarcraft/permissionsigns/container/TemporaryPermission.java b/src/main/java/net/knarcraft/permissionsigns/container/TemporaryPermission.java
index 5fef274..831023b 100644
--- a/src/main/java/net/knarcraft/permissionsigns/container/TemporaryPermission.java
+++ b/src/main/java/net/knarcraft/permissionsigns/container/TemporaryPermission.java
@@ -3,6 +3,7 @@ package net.knarcraft.permissionsigns.container;
 import org.bukkit.OfflinePlayer;
 import org.bukkit.entity.Player;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 /**
  * A temporary permission that needs to be removed after a given duration
@@ -23,7 +24,8 @@ public class TemporaryPermission implements Comparable<TemporaryPermission> {
      * @param duration       <p>The duration, in seconds, the temporary permission should last</p>
      * @param world          <p>The world the permission should be added to</p>
      */
-    public TemporaryPermission(Player player, String permissionNode, int duration, String world) {
+    public TemporaryPermission(@NotNull Player player, @NotNull String permissionNode, int duration,
+                               @Nullable String world) {
         grantedTime = System.currentTimeMillis();
         this.grantedPlayer = player;
         this.permissionNode = permissionNode;
@@ -40,7 +42,8 @@ public class TemporaryPermission implements Comparable<TemporaryPermission> {
      * @param duration       <p>The duration, in seconds, the temporary permission should last</p>
      * @param world          <p>The world the permission should be added to</p>
      */
-    public TemporaryPermission(OfflinePlayer player, String permissionNode, long grantedTime, int duration, String world) {
+    public TemporaryPermission(@NotNull OfflinePlayer player, @NotNull String permissionNode, long grantedTime,
+                               int duration, @Nullable String world) {
         this.grantedPlayer = player;
         this.permissionNode = permissionNode;
         this.grantedTime = grantedTime;
@@ -71,7 +74,7 @@ public class TemporaryPermission implements Comparable<TemporaryPermission> {
      *
      * @return <p>The player this temporary permission was granted to</p>
      */
-    public OfflinePlayer getGrantedPlayer() {
+    public @NotNull OfflinePlayer getGrantedPlayer() {
         return grantedPlayer;
     }
 
@@ -80,7 +83,7 @@ public class TemporaryPermission implements Comparable<TemporaryPermission> {
      *
      * @return <p>The permission node that was granted to this player</p>
      */
-    public String getPermissionNode() {
+    public @NotNull String getPermissionNode() {
         return permissionNode;
     }
 
@@ -89,7 +92,7 @@ public class TemporaryPermission implements Comparable<TemporaryPermission> {
      *
      * @return <p>The world the permission node should be added to</p>
      */
-    public String getWorld() {
+    public @Nullable String getWorld() {
         return world;
     }
 
diff --git a/src/main/java/net/knarcraft/permissionsigns/formatting/StringFormatter.java b/src/main/java/net/knarcraft/permissionsigns/formatting/StringFormatter.java
index 0218324..633d7ee 100644
--- a/src/main/java/net/knarcraft/permissionsigns/formatting/StringFormatter.java
+++ b/src/main/java/net/knarcraft/permissionsigns/formatting/StringFormatter.java
@@ -1,6 +1,7 @@
 package net.knarcraft.permissionsigns.formatting;
 
 import net.md_5.bungee.api.ChatColor;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -18,7 +19,8 @@ public class StringFormatter {
      * @param replacement <p>The replacement value</p>
      * @return <p>The input string with the placeholder replaced</p>
      */
-    public static String replacePlaceholder(String input, String placeholder, String replacement) {
+    public static @NotNull String replacePlaceholder(@NotNull String input, @NotNull String placeholder,
+                                                     @NotNull String replacement) {
         return input.replace(placeholder, replacement);
     }
 
@@ -30,7 +32,8 @@ public class StringFormatter {
      * @param replacements <p>The replacement values</p>
      * @return <p>The input string with placeholders replaced</p>
      */
-    public static String replacePlaceholders(String input, String[] placeholders, String[] replacements) {
+    public static @NotNull String replacePlaceholders(@NotNull String input, @NotNull String[] placeholders,
+                                                      @NotNull String[] replacements) {
         for (int i = 0; i < Math.min(placeholders.length, replacements.length); i++) {
             input = replacePlaceholder(input, placeholders[i], replacements[i]);
         }
@@ -43,7 +46,7 @@ public class StringFormatter {
      * @param translatableMessage <p>The translatable message to translate and format</p>
      * @return <p>The translated and formatted message</p>
      */
-    public static String getTranslatedInfoMessage(TranslatableMessage translatableMessage) {
+    public static @NotNull String getTranslatedInfoMessage(@NotNull TranslatableMessage translatableMessage) {
         return formatInfoMessage(Translator.getTranslatedMessage(translatableMessage));
     }
 
@@ -53,7 +56,7 @@ public class StringFormatter {
      * @param translatableMessage <p>The translatable message to translate and format</p>
      * @return <p>The translated and formatted message</p>
      */
-    public static String getTranslatedErrorMessage(TranslatableMessage translatableMessage) {
+    public static @NotNull String getTranslatedErrorMessage(@NotNull TranslatableMessage translatableMessage) {
         return formatErrorMessage(Translator.getTranslatedMessage(translatableMessage));
     }
 
@@ -63,7 +66,7 @@ public class StringFormatter {
      * @param message <p>The message to format</p>
      * @return <p>The formatted message</p>
      */
-    public static String formatInfoMessage(String message) {
+    public static @NotNull String formatInfoMessage(@NotNull String message) {
         return ChatColor.DARK_GREEN + formatMessage(message);
     }
 
@@ -73,7 +76,7 @@ public class StringFormatter {
      * @param message <p>The message to format</p>
      * @return <p>The formatted message</p>
      */
-    public static String formatErrorMessage(String message) {
+    public static @NotNull String formatErrorMessage(@NotNull String message) {
         return ChatColor.DARK_RED + formatMessage(message);
     }
 
@@ -83,7 +86,7 @@ public class StringFormatter {
      * @param message <p>The message to format</p>
      * @return <p>The formatted message</p>
      */
-    private static String formatMessage(String message) {
+    private static @NotNull String formatMessage(@NotNull String message) {
         return Translator.getTranslatedMessage(TranslatableMessage.PREFIX) + " " +
                 ChatColor.RESET + message;
     }
@@ -94,7 +97,7 @@ public class StringFormatter {
      * @param message <p>The string to search for color codes</p>
      * @return <p>The message with color codes translated</p>
      */
-    public static String translateAllColorCodes(String message) {
+    public static @NotNull String translateAllColorCodes(@NotNull String message) {
         message = ChatColor.translateAlternateColorCodes('&', message);
         Pattern pattern = Pattern.compile("(#[a-fA-F0-9]{6})");
         Matcher matcher = pattern.matcher(message);
diff --git a/src/main/java/net/knarcraft/permissionsigns/formatting/Translator.java b/src/main/java/net/knarcraft/permissionsigns/formatting/Translator.java
index 0ae9b37..5b18fde 100644
--- a/src/main/java/net/knarcraft/permissionsigns/formatting/Translator.java
+++ b/src/main/java/net/knarcraft/permissionsigns/formatting/Translator.java
@@ -3,6 +3,8 @@ package net.knarcraft.permissionsigns.formatting;
 import net.knarcraft.permissionsigns.PermissionSigns;
 import net.knarcraft.permissionsigns.utility.FileHelper;
 import org.bukkit.configuration.file.YamlConfiguration;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.io.BufferedReader;
 import java.io.File;
@@ -29,7 +31,7 @@ public final class Translator {
     /**
      * Loads the languages used by this translator
      */
-    public static void loadLanguages(String selectedLanguage) {
+    public static void loadLanguages(@NotNull String selectedLanguage) {
         backupTranslatedMessages = loadTranslatedMessages("en");
         translatedMessages = loadCustomTranslatedMessages(selectedLanguage);
         if (translatedMessages == null) {
@@ -43,7 +45,7 @@ public final class Translator {
      * @param translatableMessage <p>The message to translate</p>
      * @return <p>The translated message</p>
      */
-    public static String getTranslatedMessage(TranslatableMessage translatableMessage) {
+    public static @NotNull String getTranslatedMessage(@NotNull TranslatableMessage translatableMessage) {
         if (translatedMessages == null) {
             return "Translated strings not loaded";
         }
@@ -64,7 +66,7 @@ public final class Translator {
      * @param language <p>The language chosen by the user</p>
      * @return <p>A mapping of all strings for the given language</p>
      */
-    public static Map<TranslatableMessage, String> loadTranslatedMessages(String language) {
+    public static @Nullable Map<TranslatableMessage, String> loadTranslatedMessages(@NotNull String language) {
         try {
             BufferedReader reader = FileHelper.getBufferedReaderForInternalFile("/strings.yml");
             return loadTranslatableMessages(language, reader);
@@ -80,7 +82,7 @@ public final class Translator {
      * @param language <p>The selected language</p>
      * @return <p>The loaded translated strings, or null if no custom language file exists</p>
      */
-    public static Map<TranslatableMessage, String> loadCustomTranslatedMessages(String language) {
+    public static @Nullable Map<TranslatableMessage, String> loadCustomTranslatedMessages(@NotNull String language) {
         File strings = new File(PermissionSigns.getInstance().getDataFolder(), "strings.yml");
         if (!strings.exists()) {
             PermissionSigns.getInstance().getLogger().log(Level.FINEST, "Strings file not found");
diff --git a/src/main/java/net/knarcraft/permissionsigns/listener/BlockListener.java b/src/main/java/net/knarcraft/permissionsigns/listener/BlockListener.java
index f97e182..fd9ddb7 100644
--- a/src/main/java/net/knarcraft/permissionsigns/listener/BlockListener.java
+++ b/src/main/java/net/knarcraft/permissionsigns/listener/BlockListener.java
@@ -21,6 +21,8 @@ import org.bukkit.event.block.BlockExplodeEvent;
 import org.bukkit.event.block.BlockPistonExtendEvent;
 import org.bukkit.event.block.BlockPistonRetractEvent;
 import org.bukkit.event.entity.EntityExplodeEvent;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -33,27 +35,27 @@ import static net.knarcraft.permissionsigns.PermissionSigns.extensiveSignProtect
 public class BlockListener implements Listener {
 
     @EventHandler(priority = EventPriority.LOWEST)
-    public void onPistonExtend(BlockPistonExtendEvent event) {
+    public void onPistonExtend(@NotNull BlockPistonExtendEvent event) {
         preventDestruction(event.getBlocks(), event);
     }
 
     @EventHandler(priority = EventPriority.LOWEST)
-    public void onPistonRetract(BlockPistonRetractEvent event) {
+    public void onPistonRetract(@NotNull BlockPistonRetractEvent event) {
         preventDestruction(event.getBlocks(), event);
     }
 
     @EventHandler(priority = EventPriority.LOWEST)
-    public void onBlockExplode(BlockExplodeEvent event) {
+    public void onBlockExplode(@NotNull BlockExplodeEvent event) {
         preventDestruction(event.blockList(), event);
     }
 
     @EventHandler(priority = EventPriority.LOWEST)
-    public void onEntityExplode(EntityExplodeEvent event) {
+    public void onEntityExplode(@NotNull EntityExplodeEvent event) {
         preventDestruction(event.blockList(), event);
     }
 
     @EventHandler(priority = EventPriority.LOWEST)
-    public void onBlockBreak(BlockBreakEvent event) {
+    public void onBlockBreak(@NotNull BlockBreakEvent event) {
         Block block = event.getBlock();
         Player player = event.getPlayer();
 
@@ -81,7 +83,8 @@ public class BlockListener implements Listener {
      * @param player    <p>The player breaking the block</p>
      * @param direction <p>The direction to check for affected blocks</p>
      */
-    private void protectSignsInDirection(Cancellable event, Block block, Player player, BlockFace direction) {
+    private void protectSignsInDirection(@NotNull Cancellable event, @NotNull Block block, @Nullable Player player,
+                                         @NotNull BlockFace direction) {
         Block directionBlock = block.getRelative(direction);
         while ((direction == BlockFace.DOWN && directionBlock.getBlockData().getMaterial() ==
                 Material.POINTED_DRIPSTONE) || (direction == BlockFace.UP &&
@@ -100,7 +103,7 @@ public class BlockListener implements Listener {
      * @param blocks <p>The blocks affected by the event</p>
      * @param event  <p>The event to cancel if a permission sign is found</p>
      */
-    private void preventDestruction(List<Block> blocks, Cancellable event) {
+    private void preventDestruction(@NotNull List<Block> blocks, @NotNull Cancellable event) {
         //Don't do anything if indirect protection is disabled
         if (!PermissionSigns.indirectProtectionEnabled()) {
             return;
@@ -128,7 +131,7 @@ public class BlockListener implements Listener {
      * @param block  <p>The block to check if it's a sign</p>
      * @param player <p>The player breaking the block</p>
      */
-    private void protectBlockIfPermissionSign(Cancellable event, Block block, Player player) {
+    private void protectBlockIfPermissionSign(@NotNull Cancellable event, @NotNull Block block, @Nullable Player player) {
         //Protect the permission sign itself
         Material material = block.getBlockData().getMaterial();
         if (Tag.SIGNS.isTagged(material)) {
@@ -148,7 +151,7 @@ public class BlockListener implements Listener {
      * @param block  <p>The block to check if it's a sign</p>
      * @param player <p>The player breaking the block</p>
      */
-    private void lookForAdjacentPermissionSigns(Cancellable event, Block block, Player player) {
+    private void lookForAdjacentPermissionSigns(@NotNull Cancellable event, @NotNull Block block, @Nullable Player player) {
         Block aboveBlock = block.getRelative(BlockFace.UP);
         if (Tag.STANDING_SIGNS.isTagged(aboveBlock.getBlockData().getMaterial())) {
             checkIfBlockIsPermissionSign(aboveBlock, player, event);
@@ -177,7 +180,7 @@ public class BlockListener implements Listener {
      * @param player <p>The player that caused the event</p>
      * @param event  <p>The triggered event</p>
      */
-    private void checkIfBlockIsPermissionSign(Block block, Player player, Cancellable event) {
+    private void checkIfBlockIsPermissionSign(@NotNull Block block, @Nullable Player player, @NotNull Cancellable event) {
         Sign sign = (Sign) block.getState();
         boolean registered = SignManager.getSign(sign.getLocation()) != null;
         if (!registered) {
@@ -206,7 +209,7 @@ public class BlockListener implements Listener {
      *
      * @return <p>The relevant block faces for checking around a block</p>
      */
-    private List<BlockFace> getRelevantBlockFaces() {
+    private @NotNull List<BlockFace> getRelevantBlockFaces() {
         List<BlockFace> relevantBlockFaces = new ArrayList<>();
         relevantBlockFaces.add(BlockFace.WEST);
         relevantBlockFaces.add(BlockFace.EAST);
@@ -221,7 +224,7 @@ public class BlockListener implements Listener {
      * @param material <p>The material to check</p>
      * @return <p>True if the material is affected by gravity</p>
      */
-    private boolean isAffectedByGravity(Material material) {
+    private boolean isAffectedByGravity(@NotNull Material material) {
         //TODO: Find a better way of deciding which blocks are affected by gravity
         return Tag.SAND.isTagged(material) || Tag.ANVIL.isTagged(material) || material == Material.POINTED_DRIPSTONE ||
                 Tag.STANDING_SIGNS.isTagged(material) || material == Material.DRAGON_EGG || material == Material.GRAVEL ||
diff --git a/src/main/java/net/knarcraft/permissionsigns/listener/PlayerListener.java b/src/main/java/net/knarcraft/permissionsigns/listener/PlayerListener.java
index 19d177a..c6985ef 100644
--- a/src/main/java/net/knarcraft/permissionsigns/listener/PlayerListener.java
+++ b/src/main/java/net/knarcraft/permissionsigns/listener/PlayerListener.java
@@ -5,6 +5,7 @@ import net.knarcraft.permissionsigns.manager.PermissionManager;
 import org.bukkit.event.EventHandler;
 import org.bukkit.event.Listener;
 import org.bukkit.event.player.PlayerJoinEvent;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.PriorityQueue;
 import java.util.Queue;
@@ -15,7 +16,7 @@ import java.util.Queue;
 public class PlayerListener implements Listener {
 
     @EventHandler
-    public void onPlayerJoin(PlayerJoinEvent event) {
+    public void onPlayerJoin(@NotNull PlayerJoinEvent event) {
         //Give the joining player any temporary permissions containing their UUID
         Queue<TemporaryPermission> temporaryPermissions = new PriorityQueue<>(PermissionManager.getTemporaryPermissions());
         temporaryPermissions.removeIf((item) -> !item.getGrantedPlayer().getUniqueId().equals(event.getPlayer().getUniqueId()));
diff --git a/src/main/java/net/knarcraft/permissionsigns/listener/SignListener.java b/src/main/java/net/knarcraft/permissionsigns/listener/SignListener.java
index 92c500d..7ac1057 100644
--- a/src/main/java/net/knarcraft/permissionsigns/listener/SignListener.java
+++ b/src/main/java/net/knarcraft/permissionsigns/listener/SignListener.java
@@ -22,6 +22,7 @@ import org.bukkit.event.Listener;
 import org.bukkit.event.block.Action;
 import org.bukkit.event.player.PlayerInteractEvent;
 import org.bukkit.inventory.EquipmentSlot;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.Arrays;
 import java.util.List;
@@ -38,7 +39,7 @@ public class SignListener implements Listener {
      * @param event <p>The player interact event which was triggered</p>
      */
     @EventHandler
-    public void onPlayerInteract(PlayerInteractEvent event) {
+    public void onPlayerInteract(@NotNull PlayerInteractEvent event) {
         Player player = event.getPlayer();
         Block block = event.getClickedBlock();
 
@@ -53,8 +54,6 @@ public class SignListener implements Listener {
 
         Sign sign = (Sign) block.getState();
         if (event.getHand() == EquipmentSlot.HAND) {
-            // Cancel the interaction to avoid sign editing
-            event.setCancelled(true);
             handleSignClick(sign, player, event.getAction(), event);
         }
     }
@@ -67,7 +66,8 @@ public class SignListener implements Listener {
      * @param action <p>The hand the player used to interact with the sign</p>
      * @param event  <p>The player interact event which was triggered</p>
      */
-    private void handleSignClick(Sign sign, Player player, Action action, PlayerInteractEvent event) {
+    private void handleSignClick(@NotNull Sign sign, @NotNull Player player, @NotNull Action action,
+                                 @NotNull PlayerInteractEvent event) {
         //Check if the sign is a registered permission sign
         PermissionSign permissionSign = SignManager.getSign(sign.getLocation());
         if (permissionSign != null) {
@@ -79,9 +79,9 @@ public class SignListener implements Listener {
                 player.sendMessage(StringFormatter.getTranslatedErrorMessage(TranslatableMessage.INTERACT_PERMISSION_MISSING));
                 return;
             }
+            //Prevent placement of any blocks, and sign clicking
+            event.setCancelled(true);
             if (player.isSneaking()) {
-                //Prevent placement of any blocks
-                event.setCancelled(true);
                 handlePermissionSignInteract(permissionSign, player);
             } else {
                 player.sendMessage(getSignInfoText(permissionSign));
@@ -102,7 +102,7 @@ public class SignListener implements Listener {
      * @param sign <p>The sign to get information about</p>
      * @return <p>The information to display</p>
      */
-    private String getSignInfoText(PermissionSign sign) {
+    private String getSignInfoText(@NotNull PermissionSign sign) {
         String rawSignInfo = Translator.getTranslatedMessage(TranslatableMessage.SIGN_INFO);
         StringBuilder permissionString = new StringBuilder();
         List<String> permissionNodes = sign.getPermissionNodes();
@@ -126,7 +126,7 @@ public class SignListener implements Listener {
      * @param permissionSign <p>The permission sign that was interacted with</p>
      * @param player         <p>The player that interacted with the permission sign</p>
      */
-    private void handlePermissionSignInteract(PermissionSign permissionSign, Player player) {
+    private void handlePermissionSignInteract(@NotNull PermissionSign permissionSign, @NotNull Player player) {
         //Don't allow players to pay for permissions they already own
         boolean hasAllPermissions = true;
         for (String permissionNode : permissionSign.getPermissionNodes()) {
@@ -157,7 +157,7 @@ public class SignListener implements Listener {
      * @param player         <p>The player to give permissions to</p>
      * @param permissionSign <p>The permission sign the player clicked</p>
      */
-    private void performPermissionTransaction(Player player, PermissionSign permissionSign) {
+    private void performPermissionTransaction(@NotNull Player player, @NotNull PermissionSign permissionSign) {
         EconomyManager.withdraw(player, permissionSign.getCost());
         StringJoiner permissionsJoiner = new StringJoiner(", ");
         for (String permissionNode : permissionSign.getPermissionNodes()) {
@@ -197,7 +197,8 @@ public class SignListener implements Listener {
      * @param request <p>The creation request to fulfill</p>
      * @param player  <p>The player that interacted with the sign</p>
      */
-    private void registerPermissionSign(Sign sign, SignCreationRequest request, Player player) {
+    private void registerPermissionSign(@NotNull Sign sign, @NotNull SignCreationRequest request,
+                                        @NotNull Player player) {
         SignSide frontSide = sign.getSide(Side.FRONT);
         String[] lines = frontSide.getLines();
         //Don't allow non-empty signs to be overwritten
diff --git a/src/main/java/net/knarcraft/permissionsigns/manager/EconomyManager.java b/src/main/java/net/knarcraft/permissionsigns/manager/EconomyManager.java
index 8dae776..7942413 100644
--- a/src/main/java/net/knarcraft/permissionsigns/manager/EconomyManager.java
+++ b/src/main/java/net/knarcraft/permissionsigns/manager/EconomyManager.java
@@ -3,6 +3,7 @@ package net.knarcraft.permissionsigns.manager;
 import net.milkbowl.vault.economy.Economy;
 import org.bukkit.OfflinePlayer;
 import org.bukkit.entity.Player;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * A manager that performs all Economy tasks
@@ -20,7 +21,7 @@ public final class EconomyManager {
      *
      * @param economy <p>The economy object to use for everything economy-related</p>
      */
-    public static void initialize(Economy economy) {
+    public static void initialize(@NotNull Economy economy) {
         EconomyManager.economy = economy;
     }
 
@@ -31,7 +32,7 @@ public final class EconomyManager {
      * @param cost   <p>The cost the player needs to pay</p>
      * @return <p>True if the player is able to afford the cost</p>
      */
-    public static boolean canAfford(OfflinePlayer player, double cost) {
+    public static boolean canAfford(@NotNull OfflinePlayer player, double cost) {
         return economy.has(player, cost);
     }
 
@@ -51,7 +52,7 @@ public final class EconomyManager {
      * @param player <p>The player to withdraw money from</p>
      * @param cost   <p>The amount of money to withdraw</p>
      */
-    public static void withdraw(Player player, double cost) {
+    public static void withdraw(@NotNull Player player, double cost) {
         economy.withdrawPlayer(player, cost);
     }
 
diff --git a/src/main/java/net/knarcraft/permissionsigns/manager/PermissionManager.java b/src/main/java/net/knarcraft/permissionsigns/manager/PermissionManager.java
index 5c4388e..4ec9170 100644
--- a/src/main/java/net/knarcraft/permissionsigns/manager/PermissionManager.java
+++ b/src/main/java/net/knarcraft/permissionsigns/manager/PermissionManager.java
@@ -8,6 +8,8 @@ import org.bukkit.OfflinePlayer;
 import org.bukkit.configuration.ConfigurationSection;
 import org.bukkit.configuration.file.YamlConfiguration;
 import org.bukkit.entity.Player;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.io.File;
 import java.io.IOException;
@@ -35,7 +37,7 @@ public final class PermissionManager {
      *
      * @param permission <p>The permission object to use for everything permission-related</p>
      */
-    public static void initialize(Permission permission) {
+    public static void initialize(@NotNull Permission permission) {
         PermissionManager.permission = permission;
     }
 
@@ -44,7 +46,7 @@ public final class PermissionManager {
      *
      * @return <p>The registered temporary permissions</p>
      */
-    public static Queue<TemporaryPermission> getTemporaryPermissions() {
+    public static @NotNull Queue<TemporaryPermission> getTemporaryPermissions() {
         return temporaryPermissions;
     }
 
@@ -54,7 +56,7 @@ public final class PermissionManager {
      * @param player         <p>The player to grant the permission to</p>
      * @param permissionNode <p>The permission node to grant to the player</p>
      */
-    public static void addPermission(Player player, String permissionNode) {
+    public static void addPermission(@NotNull Player player, @NotNull String permissionNode) {
         //Allow world:permission syntax
         if (permissionNode.contains(":")) {
             grantWorldPermission(player, permissionNode, false);
@@ -71,7 +73,8 @@ public final class PermissionManager {
      * @param permissionNode <p>The permission node to grant</p>
      * @param worldName      <p>The world to add the permission node to</p>
      */
-    public static void grantTemporaryPermission(Player player, String permissionNode, String worldName) {
+    public static void grantTemporaryPermission(@NotNull Player player, @NotNull String permissionNode,
+                                                @Nullable String worldName) {
         //Allow world:permission syntax
         if (permissionNode.contains(":")) {
             grantWorldPermission(player, permissionNode, true);
@@ -88,7 +91,7 @@ public final class PermissionManager {
      * @param permissionNode <p>The permission node to grant</p>
      * @param temporary      <p>Whether the permission node should be set temporarily</p>
      */
-    private static void grantWorldPermission(Player player, String permissionNode, boolean temporary) {
+    private static void grantWorldPermission(@NotNull Player player, @NotNull String permissionNode, boolean temporary) {
         String[] permissionParts = permissionNode.split(":");
         String world = permissionParts[0];
         if (world.equalsIgnoreCase("all") || world.equalsIgnoreCase("any")) {
@@ -108,7 +111,7 @@ public final class PermissionManager {
      * @param permissionNode <p>The temporary permission to grant</p>
      * @param duration       <p>The duration for which the player should keep the given permission</p>
      */
-    public static void addTemporaryPermission(Player player, String permissionNode, int duration) {
+    public static void addTemporaryPermission(@NotNull Player player, @NotNull String permissionNode, int duration) {
         String world = player.getWorld().getName();
         grantTemporaryPermission(player, permissionNode, world);
         temporaryPermissions.add(new TemporaryPermission(player, permissionNode, duration, world));
@@ -126,7 +129,7 @@ public final class PermissionManager {
      * @param offlinePlayer  <p>The player to remove the permission from</p>
      * @param permissionNode <p>The permission node to remove from the player</p>
      */
-    public static void removeTemporaryPermission(OfflinePlayer offlinePlayer, String permissionNode) {
+    public static void removeTemporaryPermission(@NotNull OfflinePlayer offlinePlayer, @NotNull String permissionNode) {
         Player player = offlinePlayer.getPlayer();
         if (player != null && player.hasPermission(permissionNode)) {
             permission.playerRemoveTransient(null, player, permissionNode);
@@ -141,7 +144,7 @@ public final class PermissionManager {
      * @param world          <p>The world to check for the permission</p>
      * @return <p>True if the player has the permission</p>
      */
-    public static boolean hasPermission(Player player, String permissionNode, String world) {
+    public static boolean hasPermission(@NotNull Player player, @NotNull String permissionNode, @NotNull String world) {
         return permission.playerHas(world, player, permissionNode);
     }
 
@@ -182,6 +185,11 @@ public final class PermissionManager {
             String[] identifierParts = key.split(",");
             OfflinePlayer player = Bukkit.getOfflinePlayer(UUID.fromString(identifierParts[0]));
             String permissionNode = permissionSection.getString(key + ".permissionNode");
+            if (permissionNode == null) {
+                PermissionSigns.getInstance().getLogger().log(Level.WARNING, "Temporary permission " + key +
+                        " has a missing permission node.");
+                continue;
+            }
             long granted = Long.parseLong(identifierParts[1]);
             int duration = permissionSection.getInt(key + ".duration", 1);
             String world = permissionSection.getString(key + ".world", null);
diff --git a/src/main/java/net/knarcraft/permissionsigns/manager/SignManager.java b/src/main/java/net/knarcraft/permissionsigns/manager/SignManager.java
index 133af72..507dcb8 100644
--- a/src/main/java/net/knarcraft/permissionsigns/manager/SignManager.java
+++ b/src/main/java/net/knarcraft/permissionsigns/manager/SignManager.java
@@ -12,6 +12,8 @@ import org.bukkit.block.sign.SignSide;
 import org.bukkit.configuration.ConfigurationSection;
 import org.bukkit.configuration.InvalidConfigurationException;
 import org.bukkit.configuration.file.YamlConfiguration;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.io.File;
 import java.io.IOException;
@@ -42,7 +44,7 @@ public final class SignManager {
      * @param signLocation <p>The location of the permission sign to get</p>
      * @return <p>The permission sign at the given location, or null if no such sign exists</p>
      */
-    public static PermissionSign getSign(Location signLocation) {
+    public static @Nullable PermissionSign getSign(@NotNull Location signLocation) {
         return managedSigns.get(signLocation);
     }
 
@@ -51,7 +53,7 @@ public final class SignManager {
      *
      * @param sign <p>The sign to add</p>
      */
-    public static void addSign(PermissionSign sign) {
+    public static void addSign(@NotNull PermissionSign sign) {
         managedSigns.put(sign.getSignLocation(), sign);
         save();
     }
@@ -61,7 +63,7 @@ public final class SignManager {
      *
      * @param location <p>The location of the sign to remove</p>
      */
-    public static void removeSign(Location location) {
+    public static void removeSign(@NotNull Location location) {
         managedSigns.remove(location);
         save();
     }
@@ -163,7 +165,8 @@ public final class SignManager {
      * @param key         <p>The sign key which is also the sign's location</p>
      * @throws InvalidConfigurationException <p>If unable to load the sign</p>
      */
-    private static void loadSign(ConfigurationSection signSection, String key) throws InvalidConfigurationException {
+    private static void loadSign(@NotNull ConfigurationSection signSection,
+                                 @NotNull String key) throws InvalidConfigurationException {
         String[] locationParts = key.split(",");
         Location signLocation;
         try {
@@ -198,7 +201,8 @@ public final class SignManager {
         int duration = signSection.getInt(key + ".duration");
         double cost = signSection.getDouble(key + ".cost");
 
-        PermissionSign loadedSign = new PermissionSign(signLocation, signName, signDescription, permissionStrings, duration, cost);
+        PermissionSign loadedSign = new PermissionSign(signLocation, signName, signDescription, permissionStrings,
+                duration, cost);
         managedSigns.put(signLocation, loadedSign);
     }
 
diff --git a/src/main/java/net/knarcraft/permissionsigns/thread/SignCreationRequestTimeoutThread.java b/src/main/java/net/knarcraft/permissionsigns/thread/SignCreationRequestTimeoutThread.java
index ce43587..cd91432 100644
--- a/src/main/java/net/knarcraft/permissionsigns/thread/SignCreationRequestTimeoutThread.java
+++ b/src/main/java/net/knarcraft/permissionsigns/thread/SignCreationRequestTimeoutThread.java
@@ -1,6 +1,7 @@
 package net.knarcraft.permissionsigns.thread;
 
 import net.knarcraft.permissionsigns.container.SignCreationRequest;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.Queue;
 
@@ -16,7 +17,7 @@ public class SignCreationRequestTimeoutThread implements Runnable {
      *
      * @param signCreationRequests <p>A pointer to the queue of sign creation requests</p>
      */
-    public SignCreationRequestTimeoutThread(Queue<SignCreationRequest> signCreationRequests) {
+    public SignCreationRequestTimeoutThread(@NotNull Queue<SignCreationRequest> signCreationRequests) {
         this.signCreationRequests = signCreationRequests;
     }
 
diff --git a/src/main/java/net/knarcraft/permissionsigns/utility/FileHelper.java b/src/main/java/net/knarcraft/permissionsigns/utility/FileHelper.java
index 54a8b99..5165415 100644
--- a/src/main/java/net/knarcraft/permissionsigns/utility/FileHelper.java
+++ b/src/main/java/net/knarcraft/permissionsigns/utility/FileHelper.java
@@ -1,5 +1,7 @@
 package net.knarcraft.permissionsigns.utility;
 
+import org.jetbrains.annotations.NotNull;
+
 import java.io.BufferedReader;
 import java.io.FileNotFoundException;
 import java.io.InputStream;
@@ -21,7 +23,7 @@ public final class FileHelper {
      * @return <p>A buffered read for reading the file</p>
      * @throws FileNotFoundException <p>If unable to get an input stream for the given file</p>
      */
-    public static BufferedReader getBufferedReaderForInternalFile(String file) throws FileNotFoundException {
+    public static @NotNull BufferedReader getBufferedReaderForInternalFile(@NotNull String file) throws FileNotFoundException {
         InputStream inputStream = FileHelper.class.getResourceAsStream(file);
         if (inputStream == null) {
             throw new FileNotFoundException("Unable to read the given file");
@@ -35,7 +37,7 @@ public final class FileHelper {
      * @param inputStream <p>The input stream to read</p>
      * @return <p>A buffered reader reading the input stream</p>
      */
-    public static BufferedReader getBufferedReaderFromInputStream(InputStream inputStream) {
+    public static @NotNull BufferedReader getBufferedReaderFromInputStream(@NotNull InputStream inputStream) {
         InputStreamReader inputStreamReader = new InputStreamReader(inputStream, StandardCharsets.UTF_8);
         return new BufferedReader(inputStreamReader);
     }
diff --git a/src/main/java/net/knarcraft/permissionsigns/utility/UpdateChecker.java b/src/main/java/net/knarcraft/permissionsigns/utility/UpdateChecker.java
index 677c85e..9deac2b 100644
--- a/src/main/java/net/knarcraft/permissionsigns/utility/UpdateChecker.java
+++ b/src/main/java/net/knarcraft/permissionsigns/utility/UpdateChecker.java
@@ -2,6 +2,8 @@ package net.knarcraft.permissionsigns.utility;
 
 import org.bukkit.plugin.Plugin;
 import org.bukkit.scheduler.BukkitScheduler;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.io.BufferedReader;
 import java.io.IOException;
@@ -25,8 +27,9 @@ public final class UpdateChecker {
     /**
      * Checks if there's a new update available, and alerts the user if necessary
      */
-    public static void checkForUpdate(Plugin plugin, String apiResourceURL, Supplier<String> getVersionMethod,
-                                      Consumer<String> setVersionMethod) {
+    public static void checkForUpdate(@NotNull Plugin plugin, @NotNull String apiResourceURL,
+                                      @NotNull Supplier<String> getVersionMethod,
+                                      @Nullable Consumer<String> setVersionMethod) {
         BukkitScheduler scheduler = plugin.getServer().getScheduler();
         scheduler.runTaskAsynchronously(plugin, () -> UpdateChecker.queryAPI(plugin, apiResourceURL, getVersionMethod,
                 setVersionMethod));
@@ -35,8 +38,9 @@ public final class UpdateChecker {
     /**
      * Queries the spigot API to check for a newer version, and informs the user
      */
-    private static void queryAPI(Plugin plugin, String APIResourceURL, Supplier<String> getVersionMethod,
-                                 Consumer<String> setVersionMethod) {
+    private static void queryAPI(@NotNull Plugin plugin, @NotNull String APIResourceURL,
+                                 @NotNull Supplier<String> getVersionMethod,
+                                 @Nullable Consumer<String> setVersionMethod) {
         try {
             InputStream inputStream = new URL(APIResourceURL).openStream();
             BufferedReader reader = FileHelper.getBufferedReaderFromInputStream(inputStream);
@@ -64,7 +68,7 @@ public final class UpdateChecker {
      * @param oldVersion <p>The old (current) plugin version</p>
      * @return <p>The string to display</p>
      */
-    public static String getUpdateAvailableString(String newVersion, String oldVersion) {
+    public static @NotNull String getUpdateAvailableString(@NotNull String newVersion, @NotNull String oldVersion) {
         return String.format(updateNotice, newVersion, oldVersion);
     }
 
@@ -75,7 +79,7 @@ public final class UpdateChecker {
      * @param newVersion <p>The new version to check</p>
      * @return <p>True if the new version is higher than the old one</p>
      */
-    public static boolean isVersionHigher(String oldVersion, String newVersion) {
+    public static boolean isVersionHigher(@NotNull String oldVersion, @NotNull String newVersion) {
         String[] oldVersionParts = oldVersion.split("\\.");
         String[] newVersionParts = newVersion.split("\\.");
         int versionLength = Math.max(oldVersionParts.length, newVersionParts.length);