@Nullable
  private static File fromMacSystemJavaTools() {
    final File symlinkDir = new File("/usr/share/maven");
    if (isValidMavenHome(symlinkDir)) {
      return symlinkDir;
    }

    // well, try to search
    final File dir = new File("/usr/share/java");
    final String[] list = dir.list();
    if (list == null || list.length == 0) {
      return null;
    }

    String home = null;
    final String prefix = "maven-";
    final int versionIndex = prefix.length();
    for (String path : list) {
      if (path.startsWith(prefix) &&
          (home == null || compareVersionNumbers(path.substring(versionIndex), home.substring(versionIndex)) > 0)) {
        home = path;
      }
    }

    if (home != null) {
      File file = new File(dir, home);
      if (isValidMavenHome(file)) {
        return file;
      }
    }

    return null;
  }
@Nullable
  private static File fromMacSystemJavaTools()