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