根据对象某一字段名，获取字段值，将List转换为Map中包含list，Key为字段值，Value为相同字段值的对象list，快速定位具有相同字段值的对象，转换之后便于在Map中根据字段值快速查找相同字段值的对象

    //List转Mappublic static <K, V> Map<K, List<V>> getMapByListAndGroup(List<V> list, String field) {Map<K, List<V>> map = new HashMap<>();if (list == null) {return map;}List<V> objList;for (V obj : list) {Class<?> clazz = obj.getClass();Field f;K fieldValue = null;try {f = clazz.getDeclaredField(field);f.setAccessible(true);fieldValue = (K) f.get(obj);} catch (Exception e) {e.printStackTrace();}if (map.containsKey(fieldValue)) {objList = map.get(fieldValue);} else {objList = new ArrayList<>();}objList.add(obj);map.put(fieldValue, objList);}return map;}