现在有一个List集合，想对该集合中的数据分组处理，想到java8中的stream，就搞来试试，非常给力！例子如下
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 | package com.maps; public class User{ private Integer id; private String type; private String name; public User(){} public User(Integer id,String type,String name){ this.id = id; this.type = type; this.name = name; } public void setId(Integer id){ this.id = id; } public Integer getId(){ return id; } public void setType(String type){ this.type = type; } public String getType(){ return type; } public void setName(String name){ this.name = name; } public String getName(){ return name; } } |
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 | package com.maps; import java.util.ArrayList; import java.util.List; import java.util.Map; import java.util.stream.Collectors; public class MainUser{ public static void main(String[] args){ List<User> list = getUserList(); Map<String,List<User>> userGroupMap = list.stream().collect(Collectors.groupingBy(User::getType)); } public static List<User> getUserList(){ User user1 = new User(1,"张三","小学"); User user2 = new User(2,"李四","小学"); User user3 = new User(3,"王五","初中"); User user4 = new User(4,"马六","高中"); List<User> list = new ArrayList<User>(); list.add(user1); list.add(user2); list.add(user3); list.add(user4); return list; } } |
运行上面例子得到下面的结果
| 1 | {高中=[com.maps.User@ 448139f0], 初中=[com.maps.User@7cca494b], 小学=[com.maps.User@7ba |