docs: public static <T> List<List<T>> groupByField(Collection<T> collection, final String fieldName) {
  		return group(collection, new Hash<T>() {
  			private List<Object> fieldNameList = new ArrayList<>();
  
  			@Override
  			public int hash(T t) {
  				if (null == t || false == BeanUtil.isBean(t.getClass())) {
  					// 非Bean放在同一子分组中
  					return 0;
  				}
  				final Object value = ReflectUtil.getFieldValue(t, fieldName);
  				int hash = fieldNameList.indexOf(value);
  				if (hash < 0) {
  					fieldNameList.add(value);
  					return fieldNameList.size() - 1;
  				} else {
  					return hash;
  				}
  			}
  		});
  	}