diff --git a/app/src/main/java/org/kiwix/kiwixmobile/webserver/WebServerHelper.java b/app/src/main/java/org/kiwix/kiwixmobile/webserver/WebServerHelper.java
index 7eb1c9a62..3696d03ab 100644
--- a/app/src/main/java/org/kiwix/kiwixmobile/webserver/WebServerHelper.java
+++ b/app/src/main/java/org/kiwix/kiwixmobile/webserver/WebServerHelper.java
@@ -2,6 +2,8 @@ package org.kiwix.kiwixmobile.webserver;
 
 import android.content.Context;
 import android.util.Log;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import java.net.InetAddress;
 import java.net.NetworkInterface;
 import java.net.SocketException;
@@ -25,12 +27,12 @@ public class WebServerHelper {
   JNIKiwixServer kiwixServer = new JNIKiwixServer(kiwixLibrary);
   private static final String TAG = "WebServerHelper";
 
-  public WebServerHelper(Context context) {
+  public WebServerHelper(@NonNull Context context) {
     this.context = context;
   }
 
-  public boolean startServerHelper(ServerStateListener stateListener,
-      ArrayList<String> selectedBooksPath) {
+  public boolean startServerHelper(@NonNull ServerStateListener stateListener,
+      @NonNull ArrayList<String> selectedBooksPath) {
 
     // 1. Get port from settings screen
     // 2. Ask user to change port in settings if port is in use.
@@ -46,7 +48,7 @@ public class WebServerHelper {
     return isServerStarted;
   }
 
-  public boolean stopAndroidWebServer(ServerStateListener stateListener) {
+  public boolean stopAndroidWebServer(@NonNull ServerStateListener stateListener) {
     if (isServerStarted) {
       kiwixServer.stop();
       isServerStarted = false;
@@ -111,7 +113,7 @@ public class WebServerHelper {
     return ip;
   }
 
-  public static String getAddress() {
+  @Nullable public static String getAddress() {
     return "http://" + getIpAddress() + ":" + port;
   }
 }
diff --git a/app/src/main/java/org/kiwix/kiwixmobile/wifi_hotspot/HotspotService.java b/app/src/main/java/org/kiwix/kiwixmobile/wifi_hotspot/HotspotService.java
index 0c8743e13..fef2348c1 100644
--- a/app/src/main/java/org/kiwix/kiwixmobile/wifi_hotspot/HotspotService.java
+++ b/app/src/main/java/org/kiwix/kiwixmobile/wifi_hotspot/HotspotService.java
@@ -14,6 +14,7 @@ import android.os.Build;
 import android.os.IBinder;
 import android.util.Log;
 import android.widget.Toast;
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.core.app.NotificationCompat;
 import org.kiwix.kiwixmobile.R;
@@ -68,7 +69,7 @@ public class HotspotService extends Service {
     notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
   }
 
-  @Override public int onStartCommand(Intent intent, int flags, int startId) {
+  @Override public int onStartCommand(@Nullable Intent intent, int flags, int startId) {
     switch (intent.getAction()) {
 
       case ACTION_IS_HOTSPOT_ENABLED:
@@ -115,7 +116,7 @@ public class HotspotService extends Service {
     return START_NOT_STICKY;
   }
 
-  @Nullable @Override public IBinder onBind(Intent intent) {
+  @Nullable @Override public IBinder onBind(@Nullable Intent intent) {
     return serviceBinder;
   }
 
@@ -176,12 +177,12 @@ public class HotspotService extends Service {
 
   public class HotspotBinder extends Binder {
 
-    public HotspotService getService() {
+    @NonNull public HotspotService getService() {
       return HotspotService.this;
     }
   }
 
-  public void registerCallBack(ServerStateListener myCallback) {
+  public void registerCallBack(@NonNull ServerStateListener myCallback) {
     serverStateListener = myCallback;
   }
 }
diff --git a/app/src/main/java/org/kiwix/kiwixmobile/wifi_hotspot/WifiHotspotManager.java b/app/src/main/java/org/kiwix/kiwixmobile/wifi_hotspot/WifiHotspotManager.java
index 4120a47a0..345d92bec 100644
--- a/app/src/main/java/org/kiwix/kiwixmobile/wifi_hotspot/WifiHotspotManager.java
+++ b/app/src/main/java/org/kiwix/kiwixmobile/wifi_hotspot/WifiHotspotManager.java
@@ -6,6 +6,7 @@ import android.net.wifi.WifiManager;
 import android.os.Build;
 import android.os.Handler;
 import android.util.Log;
+import androidx.annotation.NonNull;
 import androidx.annotation.RequiresApi;
 import org.kiwix.kiwixmobile.webserver.ServerStateListener;
 
@@ -23,14 +24,14 @@ public class WifiHotspotManager {
   WifiConfiguration currentConfig;
   private static final String TAG = "WifiHotspotManager";
 
-  public WifiHotspotManager(Context context) {
+  public WifiHotspotManager(@NonNull Context context) {
     this.context = context;
     wifiManager = (WifiManager) this.context.getSystemService(Context.WIFI_SERVICE);
   }
 
   //Workaround to turn on hotspot for Oreo versions
   @RequiresApi(api = Build.VERSION_CODES.O)
-  public void turnOnHotspot(ServerStateListener serverStateListener) {
+  public void turnOnHotspot(@NonNull ServerStateListener serverStateListener) {
       wifiManager.startLocalOnlyHotspot(new WifiManager.LocalOnlyHotspotCallback() {
 
         @Override