Java三种方法将List转换为Map的实例

import com.google测试数据mon.base.function;

import com.google测试数据mon.collect.maps;

import java.util.arraylist;

import java.util.hashmap;

import java.util.list;

import java.util.map;

public class listtomap {

   public static void main(string[] args) {

     list<user> userlist = new arraylist<>();

     user user1 = new user();

     user1.setid(1l);

     user1.setage( "12" );

     user user2 = new user();

     user2.setid(2l);

     user2.setage( "13" );

     userlist.add(user1);

     userlist.add(user2);

     map< long , user> maps = new hashmap<>();

     for (user user : userlist) {

       maps.put(user.getid(), user);

     }

     system.out.println(maps);

   }

   public static class user {

     private long id;

     private string age;

     public long getid() {

       return id;

     }

     public void setid( long id) {

       this .id = id;

     }

     public string getage() {

       return age;

     }

     public void setage(string age) {

       this .age = age;

     }

     @override

     public string tostring() {

       return "user{" +

           "id=" + id +

           ", age='" + age + '\ '' +

           '}' ;

     }

   }

}

map< long , user> maps = maps.uniqueindex(userlist, new function<user, long >() {

       @override

       public long apply(user user) {

         return user.getid();

       }

});

map< long , user> maps = userlist.stream().collect(collectors.tomap(user::getid, user -> user));