diff --git a/src/main/java/org/jabref/gui/groups/GroupTreeView.java b/src/main/java/org/jabref/gui/groups/GroupTreeView.java
index abc6e9fb460..1d2c4646dc6 100644
--- a/src/main/java/org/jabref/gui/groups/GroupTreeView.java
+++ b/src/main/java/org/jabref/gui/groups/GroupTreeView.java
@@ -7,6 +7,7 @@
 import java.util.List;
 import java.util.Optional;
 import java.util.function.Consumer;
+import java.util.stream.Collectors;
 
 import javax.inject.Inject;
 
@@ -280,12 +281,7 @@ private void updateSelection(List<TreeItem<GroupNodeViewModel>> newSelectedGroup
         if ((newSelectedGroups == null) || newSelectedGroups.isEmpty()) {
             viewModel.selectedGroupsProperty().clear();
         } else {
-            List<GroupNodeViewModel> list = new ArrayList<>();
-            for (TreeItem<GroupNodeViewModel> model : newSelectedGroups) {
-                if ((model != null) && (model.getValue() != null) && !(model.getValue().getGroupNode().getGroup() instanceof AllEntriesGroup)) {
-                    list.add(model.getValue());
-                }
-            }
+            List<GroupNodeViewModel> list = newSelectedGroups.stream().filter(model -> model != null && !(model.getValue().getGroupNode().getGroup() instanceof AllEntriesGroup)).map(TreeItem<GroupNodeViewModel>::getValue).collect(Collectors.toList());
             viewModel.selectedGroupsProperty().setAll(list);
         }
     }
@@ -304,15 +300,7 @@ private Optional<TreeItem<GroupNodeViewModel>> getTreeItemByValue(TreeItem<Group
         if (root.getValue().equals(value)) {
             return Optional.of(root);
         }
-
-        for (TreeItem<GroupNodeViewModel> child : root.getChildren()) {
-            Optional<TreeItem<GroupNodeViewModel>> treeItemByValue = getTreeItemByValue(child, value);
-            if (treeItemByValue.isPresent()) {
-                return treeItemByValue;
-            }
-        }
-
-        return Optional.empty();
+        return root.getChildren().stream().filter(child -> getTreeItemByValue(child, value).isPresent()).findFirst();
     }
 
     private ContextMenu createContextMenuForGroup(GroupNodeViewModel group) {
diff --git a/src/main/java/org/jabref/logic/util/Version.java b/src/main/java/org/jabref/logic/util/Version.java
index 11ecd279f17..e288c718064 100644
--- a/src/main/java/org/jabref/logic/util/Version.java
+++ b/src/main/java/org/jabref/logic/util/Version.java
@@ -3,8 +3,8 @@
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStreamReader;
+import java.net.HttpURLConnection;
 import java.net.URL;
-import java.net.URLConnection;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
@@ -91,7 +91,7 @@ public static Version parse(String version) {
      * Grabs all the available releases from the GitHub repository
      */
     public static List<Version> getAllAvailableVersions() throws IOException {
-        URLConnection connection = new URL(JABREF_GITHUB_RELEASES).openConnection();
+        HttpURLConnection connection = (HttpURLConnection) new URL(JABREF_GITHUB_RELEASES).openConnection();
         connection.setRequestProperty("Accept-Charset", "UTF-8");
         try (BufferedReader rd = new BufferedReader(new InputStreamReader(connection.getInputStream()))) {
 
@@ -102,6 +102,7 @@ public static List<Version> getAllAvailableVersions() throws IOException {
                 Version version = Version.parse(jsonObject.getString("tag_name").replaceFirst("v", ""));
                 versions.add(version);
             }
+            connection.disconnect();
             return versions;
         }
     }