JDK8 分类 | 易学教程

   /**
   * 根据属性分组
   *
   * @param obj
   * @param param
   * @return
   */
   public static <T> Map<Object, List<T>> groupByCollector(List<T> obj, String param) {// 分组
       return obj.parallelStream().collect(groupingBy(t -> {
           Class<? extends Object> clazz = null;
           Method getMethod = null;
           PropertyDescriptor pd = null;
           try {
               clazz = t.getClass();
               Field field = clazz.getDeclaredField(param);
               pd = new PropertyDescriptor(field.getName(), clazz);
               getMethod = pd.getReadMethod();

           } catch (NoSuchFieldException | IntrospectionException e) {
               e.printStackTrace();
           }
           try {
               return getMethod.invoke(t);
           } catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
               e.printStackTrace();
           }
           return "ERROR";
       }));
   }

   /**
   * 根据方法名
   *
   * @param obj
   * @param param
   * @return
   */
   public static <T> Map<Object, List<T>> groupByCollectorMethod(List<T> obj, String methodName) {// 分组
       return obj.parallelStream().collect(groupingBy(t -> {
           Class<? extends Object> clazz = null;
           Method getMethod = null;
           try {
               clazz = t.getClass();

               getMethod = clazz.getDeclaredMethod(methodName);
           } catch (NoSuchMethodException | SecurityException e1) {
               e1.printStackTrace();
           }

           try {
               return getMethod.invoke(t);
           } catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
               e.printStackTrace();
           }
           return "ERROR";
       }));
   }

   /**
   * 根据Map的key升序排序
   *
   * @param groupMap
   * @return
   */
   @SuppressWarnings("hiding")
   public static Map<String, List<DocumentDisplayer>> sortByKey(Map<Object, List<DocumentDisplayer>> groupMap) {

       Map<String, List<DocumentDisplayer>> result = new TreeMap<String, List<DocumentDisplayer>>(
   new Comparator<String>() {
   public int compare(String obj1, String obj2) {
   // 降序排序
   return -(obj2.compareTo(obj1));
   }
   });

       groupMap.forEach((key,value)->{
           result.put((String)key, value);
       });

       return result;
   }

来源：CSDN

作者：飞腾创客

链接：https://blog.csdn.net/qq_39716220/article/details/103469745

标签

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param

return