Java8-Stream 流基本应用-groupBy进行分组-编程知识

Java8-Stream 流基本应用-groupBy进行分组

groupBy进行分组

@Testpublic void testStreamGroupBy(){List<UserInfoModel> 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<String, List<UserInfoModel>> 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)]}