code: public static void notEmpty(Map<?, ?> map, String message) {
          if (map == null || map.isEmpty()) {
              throw new IllegalArgumentException(message);
          }
      }
docs: Assert that a Map has entries; that is, it must not be <code>null</code>
  and must have at least one entry.
  <p/>
  <pre class="code">
  Assert.notEmpty(map, &quot;Map must have entries&quot;);
  </pre>
  
  @param map     the map to check
  @param message the exception message to use if the assertion fails
  @throws IllegalArgumentException if the map is <code>null</code> or has no entries