code: public static void notEmpty(Map<?,?> map, String message) {
          if (map == null || map.size() == 0) {
              throw new IllegalArgumentException(message);
          }
      }
docs: <p>Validate that the specified argument map is neither <code>null</code>
  nor a size of zero (no elements); otherwise throwing an exception
  with the specified message.
  
  <pre>Validate.notEmpty(myMap, "The map must not be empty");</pre>
  
  @param map the map to check
  @param message the exception message if invalid
  @throws IllegalArgumentException if the map is empty