diff --git a/src/org/kde/kdeconnect/Backends/BasePairingHandler.java b/src/org/kde/kdeconnect/Backends/BasePairingHandler.java
index c353922c..4801aae5 100644
--- a/src/org/kde/kdeconnect/Backends/BasePairingHandler.java
+++ b/src/org/kde/kdeconnect/Backends/BasePairingHandler.java
@@ -51,9 +51,9 @@ public abstract class BasePairingHandler {
     }
 
 
-    protected Device mDevice;
+    protected final Device mDevice;
     protected PairStatus mPairStatus;
-    protected PairingHandlerCallback mCallback;
+    protected final PairingHandlerCallback mCallback;
 
     protected BasePairingHandler(Device device, PairingHandlerCallback callback) {
         this.mDevice = device;
diff --git a/src/org/kde/kdeconnect/Backends/BluetoothBackend/BluetoothLink.java b/src/org/kde/kdeconnect/Backends/BluetoothBackend/BluetoothLink.java
index f4b93386..dbd7cf62 100644
--- a/src/org/kde/kdeconnect/Backends/BluetoothBackend/BluetoothLink.java
+++ b/src/org/kde/kdeconnect/Backends/BluetoothBackend/BluetoothLink.java
@@ -52,7 +52,7 @@ public class BluetoothLink extends BaseLink {
 
     private boolean continueAccepting = true;
 
-    private Thread receivingThread = new Thread(new Runnable() {
+    private final Thread receivingThread = new Thread(new Runnable() {
         @Override
         public void run() {
             StringBuilder sb = new StringBuilder();
diff --git a/src/org/kde/kdeconnect/Backends/BluetoothBackend/BluetoothLinkProvider.java b/src/org/kde/kdeconnect/Backends/BluetoothBackend/BluetoothLinkProvider.java
index b5e9e081..a3112fd1 100644
--- a/src/org/kde/kdeconnect/Backends/BluetoothBackend/BluetoothLinkProvider.java
+++ b/src/org/kde/kdeconnect/Backends/BluetoothBackend/BluetoothLinkProvider.java
@@ -221,7 +221,7 @@ public class BluetoothLinkProvider extends BaseLinkProvider {
     private class ClientRunnable extends BroadcastReceiver implements Runnable {
 
         private boolean continueProcessing = true;
-        private Map<BluetoothDevice, Thread> connectionThreads = new HashMap<>();
+        private final Map<BluetoothDevice, Thread> connectionThreads = new HashMap<>();
 
         void stopProcessing() {
             continueProcessing = false;
diff --git a/src/org/kde/kdeconnect/Backends/LanBackend/LanLink.java b/src/org/kde/kdeconnect/Backends/LanBackend/LanLink.java
index d7d17b97..3553feb3 100644
--- a/src/org/kde/kdeconnect/Backends/LanBackend/LanLink.java
+++ b/src/org/kde/kdeconnect/Backends/LanBackend/LanLink.java
@@ -63,7 +63,7 @@ public class LanLink extends BaseLink {
 
     private volatile Socket socket = null;
 
-    private LinkDisconnectedCallback callback;
+    private final LinkDisconnectedCallback callback;
 
     @Override
     public void disconnect() {
diff --git a/src/org/kde/kdeconnect/Backends/LanBackend/LanLinkProvider.java b/src/org/kde/kdeconnect/Backends/LanBackend/LanLinkProvider.java
index 24d53067..e929e479 100644
--- a/src/org/kde/kdeconnect/Backends/LanBackend/LanLinkProvider.java
+++ b/src/org/kde/kdeconnect/Backends/LanBackend/LanLinkProvider.java
@@ -85,7 +85,7 @@ public class LanLinkProvider extends BaseLinkProvider implements LanLink.LinkDis
     private boolean listening = false;
 
     // To prevent infinte loop between Android < IceCream because both device can only broadcast identity package but cannot connect via TCP
-    private ArrayList<InetAddress> reverseConnectionBlackList = new ArrayList<>();
+    private final ArrayList<InetAddress> reverseConnectionBlackList = new ArrayList<>();
 
     @Override // SocketClosedCallback
     public void linkDisconnected(LanLink brokenLink) {
diff --git a/src/org/kde/kdeconnect/Device.java b/src/org/kde/kdeconnect/Device.java
index 64c8b1f1..62e741db 100644
--- a/src/org/kde/kdeconnect/Device.java
+++ b/src/org/kde/kdeconnect/Device.java
@@ -76,7 +76,7 @@ public class Device implements BaseLink.PacketReceiver {
     private PairStatus pairStatus;
 
     private final CopyOnWriteArrayList<PairingCallback> pairingCallback = new CopyOnWriteArrayList<>();
-    private Map<String, BasePairingHandler> pairingHandlers = new HashMap<>();
+    private final Map<String, BasePairingHandler> pairingHandlers = new HashMap<>();
 
     private final CopyOnWriteArrayList<BaseLink> links = new CopyOnWriteArrayList<>();
 
@@ -621,7 +621,7 @@ public class Device implements BaseLink.PacketReceiver {
         }
     }
 
-    private SendPacketStatusCallback defaultCallback = new SendPacketStatusCallback() {
+    private final SendPacketStatusCallback defaultCallback = new SendPacketStatusCallback() {
         @Override
         public void onSuccess() {
         }
diff --git a/src/org/kde/kdeconnect/Helpers/RandomHelper.java b/src/org/kde/kdeconnect/Helpers/RandomHelper.java
index ece5cecf..8b4d40cf 100644
--- a/src/org/kde/kdeconnect/Helpers/RandomHelper.java
+++ b/src/org/kde/kdeconnect/Helpers/RandomHelper.java
@@ -4,7 +4,7 @@ package org.kde.kdeconnect.Helpers;
 import java.security.SecureRandom;
 
 public class RandomHelper {
-    public static SecureRandom secureRandom = new SecureRandom();
+    public static final SecureRandom secureRandom = new SecureRandom();
 
     private static final char[] symbols = ("ABCDEFGHIJKLMNOPQRSTUVWXYZ" +
             "abcdefghijklmnopqrstuvwxyz" +
diff --git a/src/org/kde/kdeconnect/Helpers/SMSHelper.java b/src/org/kde/kdeconnect/Helpers/SMSHelper.java
index b0ef0a3f..dca4b8a8 100644
--- a/src/org/kde/kdeconnect/Helpers/SMSHelper.java
+++ b/src/org/kde/kdeconnect/Helpers/SMSHelper.java
@@ -212,7 +212,7 @@ public class SMSHelper {
      * Represent an ID used to uniquely identify a message thread
      */
     public static class ThreadID {
-        Integer threadID;
+        final Integer threadID;
         static final String lookupColumn = Telephony.Sms.THREAD_ID;
 
         public ThreadID(Integer threadID) {
@@ -319,8 +319,8 @@ public class SMSHelper {
         private static MessageLooper singleton = null;
         private static Looper looper = null;
 
-        private static Lock looperReadyLock = new ReentrantLock();
-        private static Condition looperReady = looperReadyLock.newCondition();
+        private static final Lock looperReadyLock = new ReentrantLock();
+        private static final Condition looperReady = looperReadyLock.newCondition();
 
         private MessageLooper() {
             setName("MessageHelperLooper");
diff --git a/src/org/kde/kdeconnect/Plugins/BatteryPlugin/BatteryPlugin.java b/src/org/kde/kdeconnect/Plugins/BatteryPlugin/BatteryPlugin.java
index 0064b791..5df0bfa5 100644
--- a/src/org/kde/kdeconnect/Plugins/BatteryPlugin/BatteryPlugin.java
+++ b/src/org/kde/kdeconnect/Plugins/BatteryPlugin/BatteryPlugin.java
@@ -40,7 +40,7 @@ public class BatteryPlugin extends Plugin {
     private static final int THRESHOLD_EVENT_NONE = 0;
     private static final int THRESHOLD_EVENT_BATTERY_LOW = 1;
 
-    private NetworkPacket batteryInfo = new NetworkPacket(PACKET_TYPE_BATTERY);
+    private final NetworkPacket batteryInfo = new NetworkPacket(PACKET_TYPE_BATTERY);
 
     @Override
     public String getDisplayName() {
diff --git a/src/org/kde/kdeconnect/Plugins/ClibpoardPlugin/ClipboardListener.java b/src/org/kde/kdeconnect/Plugins/ClibpoardPlugin/ClipboardListener.java
index 690f1e91..4b0bd140 100644
--- a/src/org/kde/kdeconnect/Plugins/ClibpoardPlugin/ClipboardListener.java
+++ b/src/org/kde/kdeconnect/Plugins/ClibpoardPlugin/ClipboardListener.java
@@ -37,7 +37,7 @@ public class ClipboardListener {
         void clipboardChanged(String content);
     }
 
-    private HashSet<ClipboardObserver> observers = new HashSet<>();
+    private final HashSet<ClipboardObserver> observers = new HashSet<>();
 
     private final Context context;
     private String currentContent;
diff --git a/src/org/kde/kdeconnect/Plugins/ClibpoardPlugin/ClipboardPlugin.java b/src/org/kde/kdeconnect/Plugins/ClibpoardPlugin/ClipboardPlugin.java
index 60781d38..8031566f 100644
--- a/src/org/kde/kdeconnect/Plugins/ClibpoardPlugin/ClipboardPlugin.java
+++ b/src/org/kde/kdeconnect/Plugins/ClibpoardPlugin/ClipboardPlugin.java
@@ -45,7 +45,7 @@ public class ClipboardPlugin extends Plugin {
         return true;
     }
 
-    private ClipboardListener.ClipboardObserver observer = content -> {
+    private final ClipboardListener.ClipboardObserver observer = content -> {
         NetworkPacket np = new NetworkPacket(ClipboardPlugin.PACKET_TYPE_CLIPBOARD);
         np.set("content", content);
         device.sendPacket(np);
diff --git a/src/org/kde/kdeconnect/Plugins/MousePadPlugin/KeyInputConnection.java b/src/org/kde/kdeconnect/Plugins/MousePadPlugin/KeyInputConnection.java
index 305970cb..f382a3c6 100644
--- a/src/org/kde/kdeconnect/Plugins/MousePadPlugin/KeyInputConnection.java
+++ b/src/org/kde/kdeconnect/Plugins/MousePadPlugin/KeyInputConnection.java
@@ -3,7 +3,7 @@ package org.kde.kdeconnect.Plugins.MousePadPlugin;
 import android.view.inputmethod.BaseInputConnection;
 
 class KeyInputConnection extends BaseInputConnection {
-    private KeyListenerView view;
+    private final KeyListenerView view;
 
     public KeyInputConnection(KeyListenerView targetView, boolean fullEditor) {
         super(targetView, fullEditor);
diff --git a/src/org/kde/kdeconnect/Plugins/MousePadPlugin/KeyListenerView.java b/src/org/kde/kdeconnect/Plugins/MousePadPlugin/KeyListenerView.java
index 4946e6f3..0e911179 100644
--- a/src/org/kde/kdeconnect/Plugins/MousePadPlugin/KeyListenerView.java
+++ b/src/org/kde/kdeconnect/Plugins/MousePadPlugin/KeyListenerView.java
@@ -36,7 +36,7 @@ public class KeyListenerView extends View {
 
     private String deviceId;
 
-    public static SparseIntArray SpecialKeysMap = new SparseIntArray();
+    public static final SparseIntArray SpecialKeysMap = new SparseIntArray();
 
     static {
         int i = 0;
diff --git a/src/org/kde/kdeconnect/Plugins/MousePadPlugin/PointerAccelerationProfileFactory.java b/src/org/kde/kdeconnect/Plugins/MousePadPlugin/PointerAccelerationProfileFactory.java
index eff865ac..caefe5c9 100644
--- a/src/org/kde/kdeconnect/Plugins/MousePadPlugin/PointerAccelerationProfileFactory.java
+++ b/src/org/kde/kdeconnect/Plugins/MousePadPlugin/PointerAccelerationProfileFactory.java
@@ -39,11 +39,12 @@ public class PointerAccelerationProfileFactory {
         // Higher values will reduce the amount of noise in the speed calculation
         // but will also increase latency until the acceleration kicks in.
         // 150ms seemed like a nice middle ground.
-        long freshThreshold = 150;
+        final long freshThreshold = 150;
 
         private static class TouchDeltaEvent {
-            float x, y;
-            long time;
+            final float x;
+            final float y;
+            final long time;
             TouchDeltaEvent(float x, float y, long t) {
                 this.x = x;
                 this.y = y;
@@ -51,7 +52,7 @@ public class PointerAccelerationProfileFactory {
             }
         }
 
-        private TouchDeltaEvent[] touchEventHistory = new TouchDeltaEvent[32];
+        private final TouchDeltaEvent[] touchEventHistory = new TouchDeltaEvent[32];
 
         /* add an event to the touchEventHistory array, shifting everything else in the array. */
         private void addHistory(float deltaX, float deltaY, long eventTime) {
@@ -124,7 +125,7 @@ public class PointerAccelerationProfileFactory {
     /* Pointer acceleration with mouse_delta = touch_delta * ( touch_speed ^ exponent )
      * It is similar to x.org server's Polynomial pointer acceleration profile. */
     private static class PolynomialProfile extends SpeedBasedAccelerationProfile {
-        float exponent;
+        final float exponent;
 
         PolynomialProfile(float exponent) {
             this.exponent = exponent;
diff --git a/src/org/kde/kdeconnect/Plugins/MprisPlugin/AlbumArtCache.java b/src/org/kde/kdeconnect/Plugins/MprisPlugin/AlbumArtCache.java
index f97f4c45..f87256d9 100644
--- a/src/org/kde/kdeconnect/Plugins/MprisPlugin/AlbumArtCache.java
+++ b/src/org/kde/kdeconnect/Plugins/MprisPlugin/AlbumArtCache.java
@@ -84,7 +84,7 @@ final class AlbumArtCache {
     /**
      * A list of plugins to notify on fetched album art
      */
-    private static ArrayList<MprisPlugin> registeredPlugins = new ArrayList<>();
+    private static final ArrayList<MprisPlugin> registeredPlugins = new ArrayList<>();
 
     /**
      * Initializes the disk cache. Needs to be called at least once before trying to use the cache
@@ -242,9 +242,9 @@ final class AlbumArtCache {
     }
 
     private static final class FetchURLTask extends AsyncTask<Void, Void, Boolean> {
-        private URL url;
+        private final URL url;
         private InputStream input;
-        private DiskLruCache.Editor cacheItem;
+        private final DiskLruCache.Editor cacheItem;
         private OutputStream output;
 
         /**
diff --git a/src/org/kde/kdeconnect/Plugins/MprisPlugin/MprisMediaSession.java b/src/org/kde/kdeconnect/Plugins/MprisPlugin/MprisMediaSession.java
index b22c2f3a..6ff88fac 100644
--- a/src/org/kde/kdeconnect/Plugins/MprisPlugin/MprisMediaSession.java
+++ b/src/org/kde/kdeconnect/Plugins/MprisPlugin/MprisMediaSession.java
@@ -55,7 +55,7 @@ public class MprisMediaSession implements SharedPreferences.OnSharedPreferenceCh
     private final static int MPRIS_MEDIA_NOTIFICATION_ID = 0x91b70463; // echo MprisNotification | md5sum | head -c 8
     private final static String MPRIS_MEDIA_SESSION_TAG = "org.kde.kdeconnect_tp.media_session";
 
-    private static MprisMediaSession instance = new MprisMediaSession();
+    private static final MprisMediaSession instance = new MprisMediaSession();
 
     public static MprisMediaSession getInstance() {
         return instance;
@@ -69,20 +69,20 @@ public class MprisMediaSession implements SharedPreferences.OnSharedPreferenceCh
     private String notificationDevice = null;
     private MprisPlugin.MprisPlayer notificationPlayer = null;
     //Holds the device ids for which we can display a notification
-    private HashSet<String> mprisDevices = new HashSet<>();
+    private final HashSet<String> mprisDevices = new HashSet<>();
 
     private Context context;
     private MediaSessionCompat mediaSession;
 
     //Callback for mpris plugin updates
-    private Handler mediaNotificationHandler = new Handler(Looper.getMainLooper()) {
+    private final Handler mediaNotificationHandler = new Handler(Looper.getMainLooper()) {
         @Override
         public void handleMessage(Message msg) {
             updateMediaNotification();
         }
     };
     //Callback for control via the media session API
-    private MediaSessionCompat.Callback mediaSessionCallback = new MediaSessionCompat.Callback() {
+    private final MediaSessionCompat.Callback mediaSessionCallback = new MediaSessionCompat.Callback() {
         @Override
         public void onPlay() {
             notificationPlayer.play();
diff --git a/src/org/kde/kdeconnect/Plugins/MprisPlugin/MprisPlugin.java b/src/org/kde/kdeconnect/Plugins/MprisPlugin/MprisPlugin.java
index 2d70bae8..04fe80cc 100644
--- a/src/org/kde/kdeconnect/Plugins/MprisPlugin/MprisPlugin.java
+++ b/src/org/kde/kdeconnect/Plugins/MprisPlugin/MprisPlugin.java
@@ -204,11 +204,11 @@ public class MprisPlugin extends Plugin {
     private final static String PACKET_TYPE_MPRIS = "kdeconnect.mpris";
     private final static String PACKET_TYPE_MPRIS_REQUEST = "kdeconnect.mpris.request";
 
-    private HashMap<String, MprisPlayer> players = new HashMap<>();
+    private final HashMap<String, MprisPlayer> players = new HashMap<>();
     private boolean supportAlbumArtPayload = false;
-    private HashMap<String, Handler> playerStatusUpdated = new HashMap<>();
+    private final HashMap<String, Handler> playerStatusUpdated = new HashMap<>();
 
-    private HashMap<String, Handler> playerListUpdated = new HashMap<>();
+    private final HashMap<String, Handler> playerListUpdated = new HashMap<>();
 
     @Override
     public String getDisplayName() {
diff --git a/src/org/kde/kdeconnect/Plugins/MprisReceiverPlugin/MprisReceiverPlayer.java b/src/org/kde/kdeconnect/Plugins/MprisReceiverPlugin/MprisReceiverPlayer.java
index c622be2d..be2f1cb0 100644
--- a/src/org/kde/kdeconnect/Plugins/MprisReceiverPlugin/MprisReceiverPlayer.java
+++ b/src/org/kde/kdeconnect/Plugins/MprisReceiverPlugin/MprisReceiverPlayer.java
@@ -29,9 +29,9 @@ import android.support.annotation.RequiresApi;
 @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
 class MprisReceiverPlayer {
 
-    private MediaController controller;
+    private final MediaController controller;
 
-    private String name;
+    private final String name;
 
     private boolean isPlaying;
 
diff --git a/src/org/kde/kdeconnect/Plugins/NotificationsPlugin/RepliableNotification.java b/src/org/kde/kdeconnect/Plugins/NotificationsPlugin/RepliableNotification.java
index e3aabeb5..1380f279 100644
--- a/src/org/kde/kdeconnect/Plugins/NotificationsPlugin/RepliableNotification.java
+++ b/src/org/kde/kdeconnect/Plugins/NotificationsPlugin/RepliableNotification.java
@@ -6,9 +6,9 @@ import java.util.ArrayList;
 import java.util.UUID;
 
 class RepliableNotification {
-    String id = UUID.randomUUID().toString();
+    final String id = UUID.randomUUID().toString();
     PendingIntent pendingIntent;
-    ArrayList<android.app.RemoteInput> remoteInputs = new ArrayList<>();
+    final ArrayList<android.app.RemoteInput> remoteInputs = new ArrayList<>();
     String packageName;
     String tag;
 }
diff --git a/src/org/kde/kdeconnect/Plugins/RemoteKeyboardPlugin/RemoteKeyboardPlugin.java b/src/org/kde/kdeconnect/Plugins/RemoteKeyboardPlugin/RemoteKeyboardPlugin.java
index 8264167f..49704c09 100644
--- a/src/org/kde/kdeconnect/Plugins/RemoteKeyboardPlugin/RemoteKeyboardPlugin.java
+++ b/src/org/kde/kdeconnect/Plugins/RemoteKeyboardPlugin/RemoteKeyboardPlugin.java
@@ -49,8 +49,8 @@ public class RemoteKeyboardPlugin extends Plugin {
     /**
      * Track and expose plugin instances to allow for a 'connected'-indicator in the IME:
      */
-    private static ArrayList<RemoteKeyboardPlugin> instances = new ArrayList<>();
-    private static ReentrantLock instancesLock = new ReentrantLock(true);
+    private static final ArrayList<RemoteKeyboardPlugin> instances = new ArrayList<>();
+    private static final ReentrantLock instancesLock = new ReentrantLock(true);
 
     private static ArrayList<RemoteKeyboardPlugin> getInstances() {
         return instances;
@@ -70,7 +70,7 @@ public class RemoteKeyboardPlugin extends Plugin {
         return instances.size() > 0;
     }
 
-    private static SparseIntArray specialKeyMap = new SparseIntArray();
+    private static final SparseIntArray specialKeyMap = new SparseIntArray();
 
     static {
         int i = 0;
diff --git a/src/org/kde/kdeconnect/Plugins/RunCommandPlugin/RunCommandPlugin.java b/src/org/kde/kdeconnect/Plugins/RunCommandPlugin/RunCommandPlugin.java
index d15e774f..0a7a6ef4 100644
--- a/src/org/kde/kdeconnect/Plugins/RunCommandPlugin/RunCommandPlugin.java
+++ b/src/org/kde/kdeconnect/Plugins/RunCommandPlugin/RunCommandPlugin.java
@@ -41,8 +41,8 @@ public class RunCommandPlugin extends Plugin {
     private final static String PACKET_TYPE_RUNCOMMAND = "kdeconnect.runcommand";
     private final static String PACKET_TYPE_RUNCOMMAND_REQUEST = "kdeconnect.runcommand.request";
 
-    private ArrayList<JSONObject> commandList = new ArrayList<>();
-    private ArrayList<CommandsChangedCallback> callbacks = new ArrayList<>();
+    private final ArrayList<JSONObject> commandList = new ArrayList<>();
+    private final ArrayList<CommandsChangedCallback> callbacks = new ArrayList<>();
     private final ArrayList<CommandEntry> commandItems = new ArrayList<>();
 
     private boolean canAddCommand;
diff --git a/src/org/kde/kdeconnect/Plugins/SMSPlugin/SMSPlugin.java b/src/org/kde/kdeconnect/Plugins/SMSPlugin/SMSPlugin.java
index 4222a589..ff576615 100644
--- a/src/org/kde/kdeconnect/Plugins/SMSPlugin/SMSPlugin.java
+++ b/src/org/kde/kdeconnect/Plugins/SMSPlugin/SMSPlugin.java
@@ -147,10 +147,10 @@ public class SMSPlugin extends Plugin {
     private long mostRecentTimestamp = 0;
     // Since the mostRecentTimestamp is accessed both from the plugin's thread and the ContentObserver
     // thread, make sure that access is coherent
-    private Lock mostRecentTimestampLock = new ReentrantLock();
+    private final Lock mostRecentTimestampLock = new ReentrantLock();
 
     private class MessageContentObserver extends ContentObserver {
-        SMSPlugin mPlugin;
+        final SMSPlugin mPlugin;
 
         /**
          * Create a ContentObserver to watch the Messages database. onChange is called for
diff --git a/src/org/kde/kdeconnect/Plugins/SharePlugin/ShareNotification.java b/src/org/kde/kdeconnect/Plugins/SharePlugin/ShareNotification.java
index 437c1803..ca4051ab 100644
--- a/src/org/kde/kdeconnect/Plugins/SharePlugin/ShareNotification.java
+++ b/src/org/kde/kdeconnect/Plugins/SharePlugin/ShareNotification.java
@@ -45,10 +45,10 @@ import java.io.FileNotFoundException;
 class ShareNotification {
 
     private final String filename;
-    private NotificationManager notificationManager;
-    private int notificationId;
+    private final NotificationManager notificationManager;
+    private final int notificationId;
     private NotificationCompat.Builder builder;
-    private Device device;
+    private final Device device;
 
     public ShareNotification(Device device, String filename) {
         this.device = device;
diff --git a/src/org/kde/kdeconnect/Plugins/SystemvolumePlugin/Sink.java b/src/org/kde/kdeconnect/Plugins/SystemvolumePlugin/Sink.java
index ca204f12..d5f9f375 100644
--- a/src/org/kde/kdeconnect/Plugins/SystemvolumePlugin/Sink.java
+++ b/src/org/kde/kdeconnect/Plugins/SystemvolumePlugin/Sink.java
@@ -38,7 +38,7 @@ class Sink {
     private boolean mute;
     private int maxVolume;
 
-    private List<UpdateListener> listeners;
+    private final List<UpdateListener> listeners;
 
     Sink(JSONObject obj) throws JSONException {
         listeners = new ArrayList<>();
diff --git a/src/org/kde/kdeconnect/Plugins/SystemvolumePlugin/SystemvolumeFragment.java b/src/org/kde/kdeconnect/Plugins/SystemvolumePlugin/SystemvolumeFragment.java
index f2c1681a..8f239bef 100644
--- a/src/org/kde/kdeconnect/Plugins/SystemvolumePlugin/SystemvolumeFragment.java
+++ b/src/org/kde/kdeconnect/Plugins/SystemvolumePlugin/SystemvolumeFragment.java
@@ -138,7 +138,7 @@ public class SystemvolumeFragment extends ListFragment implements Sink.UpdateLis
 
     private class UIListener implements SeekBar.OnSeekBarChangeListener, ImageButton.OnClickListener {
 
-        private Sink sink;
+        private final Sink sink;
 
         private UIListener(Sink sink) {
             this.sink = sink;
diff --git a/src/org/kde/kdeconnect/Plugins/SystemvolumePlugin/SystemvolumePlugin.java b/src/org/kde/kdeconnect/Plugins/SystemvolumePlugin/SystemvolumePlugin.java
index d63d1be4..a32f2a08 100644
--- a/src/org/kde/kdeconnect/Plugins/SystemvolumePlugin/SystemvolumePlugin.java
+++ b/src/org/kde/kdeconnect/Plugins/SystemvolumePlugin/SystemvolumePlugin.java
@@ -41,8 +41,8 @@ public class SystemvolumePlugin extends Plugin {
         void sinksChanged();
     }
 
-    private HashMap<String, Sink> sinks;
-    private ArrayList<SinkListener> listeners;
+    private final HashMap<String, Sink> sinks;
+    private final ArrayList<SinkListener> listeners;
 
     public SystemvolumePlugin() {
         sinks = new HashMap<>();
diff --git a/src/org/kde/kdeconnect/UserInterface/CustomDevicesActivity.java b/src/org/kde/kdeconnect/UserInterface/CustomDevicesActivity.java
index 96022f02..4cc09bbb 100644
--- a/src/org/kde/kdeconnect/UserInterface/CustomDevicesActivity.java
+++ b/src/org/kde/kdeconnect/UserInterface/CustomDevicesActivity.java
@@ -76,7 +76,7 @@ public class CustomDevicesActivity extends AppCompatActivity {
     }
 
     private boolean dialogAlreadyShown = false;
-    private AdapterView.OnItemClickListener onClickListener = (parent, view, position, id) -> {
+    private final AdapterView.OnItemClickListener onClickListener = (parent, view, position, id) -> {
 
         if (dialogAlreadyShown) {
             return;
diff --git a/src/org/kde/kdeconnect/UserInterface/MainActivity.java b/src/org/kde/kdeconnect/UserInterface/MainActivity.java
index 5b8803eb..82d8d5ed 100644
--- a/src/org/kde/kdeconnect/UserInterface/MainActivity.java
+++ b/src/org/kde/kdeconnect/UserInterface/MainActivity.java
@@ -349,7 +349,7 @@ public class MainActivity extends AppCompatActivity {
         void onNameChanged(String newName);
     }
 
-    private Set<NameChangeCallback> nameChangeSubscribers = new HashSet<>();
+    private final Set<NameChangeCallback> nameChangeSubscribers = new HashSet<>();
 
     public void addNameChangeCallback(NameChangeCallback cb) {
         nameChangeSubscribers.add(cb);
diff --git a/tests/org/kde/kdeconnect/LanLinkTest.java b/tests/org/kde/kdeconnect/LanLinkTest.java
index b9cc9f88..875e0210 100644
--- a/tests/org/kde/kdeconnect/LanLinkTest.java
+++ b/tests/org/kde/kdeconnect/LanLinkTest.java
@@ -108,7 +108,7 @@ class LanLinkTest extends AndroidTestCase {
         class Downloader extends Thread {
 
             NetworkPacket np;
-            ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
+            final ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
 
             void setNetworkPacket(NetworkPacket networkPacket) {
                 this.np = networkPacket;