work with jar file before closing it

src/main/java/de/szimnau/zeitlaeufer/Main.java

@@ -47,20 +47,23 @@ public class Main {
       ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
       List<String> fileNames = new ArrayList<>();
       URL jarUrl = classLoader.getResource("de/szimnau/zeitlaeufer");
+      if (jarUrl == null) {
+         throw new RuntimeException("Kann ausführbare Klassen nicht eruieren, da keine Ressource \"de/szimnau/zeitlaeufer\" verfügbar.");
+      }
       String path = jarUrl.getPath().split(":", 2)[1];
       String cleanPath = path.substring(0, path.lastIndexOf('!'));
       Enumeration<JarEntry> entries;
       try (var jarFile = new JarFile(URLDecoder.decode(cleanPath, StandardCharsets.UTF_8))) {
          entries = jarFile.entries();
-      } catch (IOException e) {
+         while (entries.hasMoreElements()) {
-         throw new RuntimeException(e);
+            JarEntry entry = entries.nextElement();
-      }
+            if (entry.isDirectory()) {
-      while (entries.hasMoreElements()) {
+               continue;
-         JarEntry entry = entries.nextElement();
+            }
-         if (entry.isDirectory()) {
+            fileNames.add(entry.getName());
-            continue;
          }
-         fileNames.add(entry.getName());
+      } catch (IOException e) {
+         throw new RuntimeException("Kann JAR-Datei zwecks Reflection nicht öffnen:", e);
       }
       var increment = new AtomicInteger();
       return Collections.unmodifiableSortedMap(new TreeMap<>(