diff --git a/app/src/main/java/com/readrops/app/database/Database.java b/app/src/main/java/com/readrops/app/database/Database.java
index 72091403..01c381fc 100644
--- a/app/src/main/java/com/readrops/app/database/Database.java
+++ b/app/src/main/java/com/readrops/app/database/Database.java
@@ -2,11 +2,9 @@ package com.readrops.app.database;
 
 import android.content.Context;
 
-import androidx.annotation.NonNull;
 import androidx.room.Room;
 import androidx.room.RoomDatabase;
 import androidx.room.TypeConverters;
-import androidx.sqlite.db.SupportSQLiteDatabase;
 
 import com.readrops.app.database.dao.AccountDao;
 import com.readrops.app.database.dao.FeedDao;
@@ -35,22 +33,8 @@ public abstract class Database extends RoomDatabase {
     public static Database getInstance(Context context) {
         if (database == null)
             database = Room.databaseBuilder(context, Database.class, "readrops-db")
-                    .addCallback(roomCallback)
                     .build();
 
         return database;
     }
-
-    public static RoomDatabase.Callback roomCallback = new RoomDatabase.Callback() {
-        @Override
-        public void onCreate(@NonNull SupportSQLiteDatabase db) {
-            super.onCreate(db);
-        }
-
-        @Override
-        public void onOpen(@NonNull SupportSQLiteDatabase db) {
-            super.onOpen(db);
-        }
-    };
-
 }
\ No newline at end of file
diff --git a/app/src/main/java/com/readrops/app/database/ItemsListQueryBuilder.java b/app/src/main/java/com/readrops/app/database/ItemsListQueryBuilder.java
index 28fb6662..1dfca1bb 100644
--- a/app/src/main/java/com/readrops/app/database/ItemsListQueryBuilder.java
+++ b/app/src/main/java/com/readrops/app/database/ItemsListQueryBuilder.java
@@ -35,14 +35,14 @@ public class ItemsListQueryBuilder {
     private String buildWhereClause() {
         StringBuilder stringBuilder = new StringBuilder(80);
 
-        stringBuilder.append("Feed.account_id = " + accountId + " And ");
+        stringBuilder.append("Feed.account_id = ").append(accountId).append(" And ");
 
         if (!showReadItems)
             stringBuilder.append("read = 0 And ");
 
         switch (filterType) {
             case FEED_FILTER:
-                stringBuilder.append("feed_id = " + filterFeedId + " And read_it_later = 0");
+                stringBuilder.append("feed_id = ").append(filterFeedId).append(" And read_it_later = 0");
                 break;
             case READ_IT_LATER_FILTER:
                 stringBuilder.append("read_it_later = 1");
diff --git a/app/src/main/java/com/readrops/app/repositories/ARepository.java b/app/src/main/java/com/readrops/app/repositories/ARepository.java
index aa8d9fdb..9a4cec80 100644
--- a/app/src/main/java/com/readrops/app/repositories/ARepository.java
+++ b/app/src/main/java/com/readrops/app/repositories/ARepository.java
@@ -17,8 +17,6 @@ import com.readrops.app.utils.Utils;
 
 import java.io.IOException;
 import java.util.List;
-import java.util.concurrent.Executor;
-import java.util.concurrent.Executors;
 
 import io.reactivex.Completable;
 import io.reactivex.Observable;
@@ -27,12 +25,9 @@ import io.reactivex.schedulers.Schedulers;
 
 public abstract class ARepository {
 
-    protected Executor executor;
-
     protected Database database;
 
     protected ARepository(Application application) {
-        executor = Executors.newSingleThreadExecutor();
         this.database = Database.getInstance(application);
     }
 
diff --git a/app/src/main/java/com/readrops/app/utils/SharedPreferencesManager.java b/app/src/main/java/com/readrops/app/utils/SharedPreferencesManager.java
index 1b32b7e1..52651fac 100644
--- a/app/src/main/java/com/readrops/app/utils/SharedPreferencesManager.java
+++ b/app/src/main/java/com/readrops/app/utils/SharedPreferencesManager.java
@@ -43,7 +43,7 @@ public final class SharedPreferencesManager {
 
     public static String readString(Context context, String key) {
         SharedPreferences sharedPreferences = getSharedPreferences(context);
-        return sharedPreferences.getString(key.toString(), null);
+        return sharedPreferences.getString(key, null);
     }
 
     public enum SharedPrefKey {
diff --git a/app/src/main/java/com/readrops/app/viewmodels/MainViewModel.java b/app/src/main/java/com/readrops/app/viewmodels/MainViewModel.java
index 729ac527..c000ed7a 100644
--- a/app/src/main/java/com/readrops/app/viewmodels/MainViewModel.java
+++ b/app/src/main/java/com/readrops/app/viewmodels/MainViewModel.java
@@ -52,7 +52,6 @@ public class MainViewModel extends AndroidViewModel {
         queryBuilder.setFilterType(FilterType.NO_FILTER);
         queryBuilder.setSortType(MainActivity.ListSortType.NEWEST_TO_OLDEST);
 
-        repository = new NextNewsRepository(application);
         db = Database.getInstance(application);
 
         itemsWithFeed = new MediatorLiveData<>();