Java8-Stream 流基本应用-groupBy进行分组

groupBy进行分组

 @Test
 public void testStreamGroupBy(){
    List result=new ArrayList<>();
  for (int i = 0; i < 10; i++) {
   UserInfoModel user=new UserInfoModel();
   user.setUserId(i+"");
   user.setUserName("kangshihang");
   result.add(user);
  }

  for (int i = 0; i < 10; i++) {
   UserInfoModel user=new UserInfoModel();
   user.setUserId(i+"");
   user.setUserName("kangshihang1");
   result.add(user);
  }
  System.out.println("分组之前的数组内容result"+result);

  //使用stream的groupBy指定属性进行分组
  Map> collect = result.stream().collect(Collectors.groupingBy(UserInfoModel::getUserName));

  System.out.println("分组之后的数组内容result"+collect);

 }

分组结果

分组之前

[UserInfoModel(userId=0, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=1, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=2, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=3, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=4, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=5, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=6, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=7, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=8, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=9, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=0, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=1, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=2, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=3, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=4, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=5, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=6, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=7, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=8, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=9, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null)]

分组之后

{kangshihang1=[UserInfoModel(userId=0, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=1, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=2, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=3, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=4, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=5, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=6, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=7, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=8, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=9, userName=kangshihang1, userPhone=null, weixinId=null, userPassword=null)],

kangshihang=[UserInfoModel(userId=0, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=1, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=2, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=3, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=4, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=5, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=6, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=7, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=8, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null), UserInfoModel(userId=9, userName=kangshihang, userPhone=null, weixinId=null, userPassword=null)]}