java通過Stream對list集合分組
現在有一個List集合，想對該集合中的數據分組處理，想到java8中的stream，就搞來試試，非常給力！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,"張三","小學");
User user2 =
new User(2,"李四","小學");
User user3 =
new User(3,"王五","初中");
User user4 =
new User(4,"馬六","高中");
List<User> list =
new ArrayList<User>();
list.add(user1);
list.add(user2);
list.add(user3);
list.add(user4);
return list;
}
}
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運行上面例子得到下面的結果
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1
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{高中=[com.maps.User@
448139f0], 初中=[com.maps.User@7cca494b], 小學=[com.maps.User@7ba
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