diff --git a/src/main/java/cz/cvut/kbss/termit/service/repository/BaseRepositoryService.java b/src/main/java/cz/cvut/kbss/termit/service/repository/BaseRepositoryService.java
index d64aaec7c..ee983b752 100644
--- a/src/main/java/cz/cvut/kbss/termit/service/repository/BaseRepositoryService.java
+++ b/src/main/java/cz/cvut/kbss/termit/service/repository/BaseRepositoryService.java
@@ -152,7 +152,7 @@ private Class<T> resolveGenericType() {
         // Adapted from https://gist.github.com/yunspace/930d4d40a787a1f6a7d1
         final List<ResolvedType> typeParameters =
                 new TypeResolver().resolve(this.getClass()).typeParametersFor(BaseRepositoryService.class);
-        assert typeParameters.size() >= 1;
+        assert !typeParameters.isEmpty();
         return (Class<T>) typeParameters.get(0).getErasedType();
     }
 
@@ -230,10 +230,9 @@ protected void preUpdate(@NonNull T instance) {
     }
 
     /**
-     * Override this method to plug custom behavior into the transactional cycle of {@link #update(HasIdentifier)} )}.
+     * Override this method to plug custom behavior into the transactional cycle of {@link #update(HasIdentifier)}.
      *
-     * @param instance The updated instance which will be returned by {@link #update(HasIdentifier)} )}, not {@code
-     *                 null}
+     * @param instance The updated instance which will be returned by {@link #update(HasIdentifier)}, not {@code null}
      */
     protected void postUpdate(@NonNull T instance) {
         // Do nothing
diff --git a/src/main/java/cz/cvut/kbss/termit/service/repository/ResourceRepositoryService.java b/src/main/java/cz/cvut/kbss/termit/service/repository/ResourceRepositoryService.java
index d4aea03bf..4bdd88dad 100644
--- a/src/main/java/cz/cvut/kbss/termit/service/repository/ResourceRepositoryService.java
+++ b/src/main/java/cz/cvut/kbss/termit/service/repository/ResourceRepositoryService.java
@@ -27,6 +27,7 @@
 import cz.cvut.kbss.termit.persistence.dao.TermOccurrenceDao;
 import cz.cvut.kbss.termit.service.IdentifierResolver;
 import cz.cvut.kbss.termit.util.Configuration;
+import org.jetbrains.annotations.NotNull;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
@@ -72,7 +73,7 @@ protected Resource mapToDto(Resource entity) {
     }
 
     @Override
-    protected void prePersist(Resource instance) {
+    protected void prePersist(@NotNull Resource instance) {
         super.prePersist(instance);
         if (instance.getUri() == null) {
             instance.setUri(idResolver.generateIdentifier(cfgNamespace.getResource(), instance.getLabel()));
@@ -97,17 +98,16 @@ public void persist(Resource resource, Vocabulary vocabulary) {
     }
 
     @Override
-    protected void preRemove(Resource instance) {
+    protected void preRemove(@NotNull Resource instance) {
         LOG.trace("Removing term occurrences in resource {} which is about to be removed.", instance);
         termOccurrenceDao.removeAll(instance);
         removeFromParentDocumentIfFile(instance);
     }
 
     private void removeFromParentDocumentIfFile(Resource instance) {
-        if (!(instance instanceof File)) {
+        if (!(instance instanceof File file)) {
             return;
         }
-        final File file = (File) instance;
         final Document parent = file.getDocument();
         if (parent != null) {
             LOG.trace("Removing file {} from its parent document {}.", instance, parent);
diff --git a/src/main/java/cz/cvut/kbss/termit/service/repository/TermRepositoryService.java b/src/main/java/cz/cvut/kbss/termit/service/repository/TermRepositoryService.java
index 57c642a36..f9b09a1b7 100644
--- a/src/main/java/cz/cvut/kbss/termit/service/repository/TermRepositoryService.java
+++ b/src/main/java/cz/cvut/kbss/termit/service/repository/TermRepositoryService.java
@@ -125,7 +125,7 @@ private void pruneEmptyTranslations(Term instance) {
     }
 
     @Override
-    protected void postUpdate(Term instance) {
+    protected void postUpdate(@NotNull Term instance) {
         final Vocabulary vocabulary = vocabularyService.getRequiredReference(instance.getVocabulary());
         if (instance.hasParentInSameVocabulary()) {
             vocabulary.getGlossary().removeRootTerm(instance);
@@ -427,7 +427,7 @@ protected void preRemove(@NotNull Term instance) {
     }
 
     @Override
-    protected void postRemove(Term instance) {
+    protected void postRemove(@NotNull Term instance) {
         super.postRemove(instance);
         if (!instance.hasParentInSameVocabulary()) {
             final Vocabulary v = vocabularyService.findRequired(instance.getVocabulary());
diff --git a/src/main/java/cz/cvut/kbss/termit/service/repository/UserRepositoryService.java b/src/main/java/cz/cvut/kbss/termit/service/repository/UserRepositoryService.java
index 4437cc833..3daf1bb1d 100644
--- a/src/main/java/cz/cvut/kbss/termit/service/repository/UserRepositoryService.java
+++ b/src/main/java/cz/cvut/kbss/termit/service/repository/UserRepositoryService.java
@@ -23,6 +23,7 @@
 import cz.cvut.kbss.termit.persistence.dao.UserAccountDao;
 import cz.cvut.kbss.termit.service.IdentifierResolver;
 import cz.cvut.kbss.termit.util.Configuration;
+import org.jetbrains.annotations.NotNull;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.security.crypto.password.PasswordEncoder;
 import org.springframework.stereotype.Service;
@@ -72,13 +73,13 @@ protected UserAccount mapToDto(UserAccount entity) {
     }
 
     @Override
-    protected UserAccount postLoad(UserAccount instance) {
+    protected UserAccount postLoad(@NotNull UserAccount instance) {
         instance.erasePassword();
         return instance;
     }
 
     @Override
-    protected void prePersist(UserAccount instance) {
+    protected void prePersist(@NotNull UserAccount instance) {
         super.prePersist(instance);
         if (instance.getUri() == null) {
             instance.setUri(idResolver
@@ -90,7 +91,7 @@ protected void prePersist(UserAccount instance) {
     }
 
     @Override
-    protected void preUpdate(UserAccount instance) {
+    protected void preUpdate(@NotNull UserAccount instance) {
         final UserAccount original = userAccountDao.find(instance.getUri()).orElseThrow(
                 () -> new NotFoundException("User " + instance + " does not exist."));
         if (instance.getPassword() != null) {