code: public static long gcd(List<Long> l) {
          if (l.isEmpty()) {
              throw new IllegalArgumentException("List must contain at least one element");
          }
          BigInteger gcd = BigInteger.valueOf(l.get(0));
          for (Long num : l.subList(1, l.size())) {
              gcd = gcd.gcd(BigInteger.valueOf(num));
          }
          return gcd.longValue();
          
      }
docs: Finds the greatest common divisor of all numbers in the list.
  
  @return the GCD or Long.MAX_VALUE if the list is empty.