java数据按时间分组_java list集合按日期分组

亦凉 2022-11-03 04:01 760阅读 0赞

结果：

"code": 1,

"data": \{

"mapDate": \[

"fomTime": "2019-11-14",

"list": \[

"id": 0,

"userId": 1,

"viewerId": 3,

"nickname": "用户3",

"headImage": "http://cdn.duitang.com/uploads/blog/201404/22/20140422142715\_8GtUk.thumb.600\_0.jpeg",

"isMaster": 0,

"code": null,

"pendantIcon": null,

"isFriend": 0,

"createTime": "2019-11-14T10:53:05",

"friendId": null,

"fomTime": "2019-11-14"

\},

"fomTime": "2019-11-13",

"list": \[

"id": 0,

"userId": 1,

"viewerId": 2,

"nickname": "用户2",

"headImage": "http://cdn.duitang.com/uploads/blog/201404/22/20140422142715\_8GtUk.thumb.600\_0.jpeg",

"isMaster": 0,

"code": 1000,

"pendantIcon": null,

"isFriend": 1,

"createTime": "2019-11-13T10:52:58",

"friendId": 1,

"fomTime": "2019-11-13"

\},

"fomTime": "2019-11-12",

"list": \[

"id": 0,

"userId": 1,

"viewerId": 4,

"nickname": "用户4",

"headImage": "http://cdn.duitang.com/uploads/blog/201404/22/20140422142715\_8GtUk.thumb.600\_0.jpeg",

"isMaster": 0,

"code": 1001,

"pendantIcon": null,

"isFriend": 1,

"createTime": "2019-11-12T10:53:44",

"friendId": 1,

"fomTime": "2019-11-12"

代码：

controller ：

public AjaxResult selectViewer(Long userId)\{

Page page = new Page(1, 20); //无用

List mapDate = userByWatchService.selectViewer(userId, page);

Map map = new HashMap<>();

map.put("mapDate", mapDate);

return AjaxResult.success(map);

service :

public List selectViewer(Long userId, Page page) \{

//按日期分组

Map> resultList=list.stream().collect(Collectors.groupingBy(UserByWatch::getFomTime));

Object\[\] keyArr=resultList.keySet().toArray(); //获取resultList的所有key值数组

Arrays.sort(keyArr);

List userByWatches=new ArrayList<>();

for(int i=keyArr.length-1;i>=0;i--)\{

UserByWatchVo userByWatchVo=new UserByWatchVo();

userByWatchVo.setFomTime((String)keyArr\[i\]);

userByWatchVo.setList(resultList.get(keyArr\[i\]));

userByWatches.add(userByWatchVo);

return userByWatches;

mapper：

List selectViewer(@Param("userId") Long userId, Page page);

mapper.xml:

SELECT

t\_user\_by\_watch.user\_id as userId,

t\_user\_data.id as viewerId,

t\_user\_data.nickname as nickname,

t\_friend\_user.friend\_id as friendId,

t\_user\_by\_watch.create\_time as createTime,

date\_format(t\_user\_by\_watch.create\_time,'%Y-%m-%d' ) as fomTime

FROM

t\_user\_by\_watch

left JOIN t\_user\_data ON t\_user\_by\_watch.viewer\_id = t\_user\_data.id

left JOIN t\_friend\_user ON (t\_user\_data.id = t\_friend\_user.user\_id and t\_friend\_user.friend\_id=\#\{userId\})

where t\_user\_by\_watch.user\_id=\#\{userId\}

order by createTime desc

UserByWatchVo 类：

package com.mbyte.easy.admin.vo;

import com.mbyte.easy.admin.entity.UserByWatch;

import lombok.Data;

import java.util.List;

@Data

public class UserByWatchVo \{

private String fomTime;

private Listlist;

UserByWatch 类：

package com.mbyte.easy.admin.entity;

import com.baomidou.mybatisplus.annotation.TableField;

import com.baomidou.mybatisplus.annotation.TableName;

import com.mbyte.easy.common.entity.BaseEntity;

import java.time.LocalDateTime;

import io.swagger.annotations.ApiModel;

import io.swagger.annotations.ApiModelProperty;

import lombok.Data;

import lombok.EqualsAndHashCode;

import lombok.experimental.Accessors;

@Data

@TableName("t\_user\_by\_watch")

public class UserByWatch extends BaseEntity \{

private static final long serialVersionUID = 1L;

/\*\*

\* 用户id

\*/

@ApiModelProperty(value = "用户id",name = "userId")

private Long userId;

/\*\*

\* 观看者id

\*/

@ApiModelProperty(value = "观看者id",name = "viewerId")

private Long viewerId;

/\*\*

\* 观看者昵称

\*/

@ApiModelProperty(value = "观看者昵称",name = "nickname")

@TableField(exist = false)

private String nickname;

/\*\*

\* 创建时间

\*/

@ApiModelProperty(value = "创建时间",name = "createTime")

private LocalDateTime createTime;

@TableField(exist = false)

private Long friendId;

/\*\*

\* 用于分类的时间

\*/

@TableField(exist = false)

private String fomTime;

java数据按时间分组_java list集合按日期分组

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