java通过Stream对list集合分组

java通过Stream对list集合分组

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

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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; } }

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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