code: public static String getMacOsMajorVersion() {
          if (!isMacOs()) {
              return null;
          }
  
          String osVersion = System.getProperty("os.version");
  
          if (osVersion != null) {
              String[] split = osVersion.split("\\.");
              if (split.length >= 2) {
                  return split[0] + "." + split[1];
              } else {
                  return osVersion;
              }
          }
  
          return null;
      }
docs: Tries to get the current version of MacOS/MacOS X.
  The version usually looks like '10.13.4', where the part behind the last dot represents the patchlevel.
  The major version in this case would be '10.13'.
  @return version without patchlevel or null