code: public static <K, V> Map<K, V> notEmpty(Map<K, V> map) throws IllegalArgumentException {
  		return notEmpty(map, "[Assertion failed] - this map must not be empty; it must contain at least one entry");
  	}
docs: 断言给定Map非空
  
  <pre class="code">
  Assert.notEmpty(map, "Map must have entries");
  </pre>
  
  @param <K> Key类型
  @param <V> Value类型
  
  @param map 被检查的Map
  @return 被检查的Map
  @throws IllegalArgumentException if the map is {@code null} or has no entries