protected static @Nullable String findMavenGroupId(@NotNull VirtualFile classesJar, String artifactId) {
    try (JarFile jarFile = new JarFile(VfsUtilCore.virtualToIoFile(classesJar))) {
      final Enumeration<JarEntry> entries = jarFile.entries();
      while (entries.hasMoreElements()) {
        JarEntry entry = entries.nextElement();
        final String name = entry.getName();
        if (StringUtil.startsWith(name, MAVEN_POM_ENTRY_PREFIX) && StringUtil.endsWith(name, "/" + artifactId + "/pom.xml")) {
          final int index = name.indexOf('/', MAVEN_POM_ENTRY_PREFIX.length());
          return index != -1 ? name.substring(MAVEN_POM_ENTRY_PREFIX.length(), index) : null;
        }
      }
    }
    catch (IOException ignore) {
    }
    return null;
  }
protected static @Nullable String findMavenGroupId(@NotNull VirtualFile classesJar, String artifactId)