java8中List根据某一字段去重
Posted diweikang
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实体类:
package test;
public class User
private String userid;
private String username;
private String age;
private String address;
public User(String userid, String username, String age, String address)
super();
this.userid = userid;
this.username = username;
this.age = age;
this.address = address;
public String getUserid()
return userid;
public void setUserid(String userid)
this.userid = userid;
public String getUsername()
return username;
public void setUsername(String username)
this.username = username;
public String getAge()
return age;
public void setAge(String age)
this.age = age;
public String getAddress()
return address;
public void setAddress(String address)
this.address = address;
@Override
public String toString()
return "User [userid=" + userid + ", username=" + username + ", age=" + age + ", address=" + address + "]";
测试:
package test;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.TreeSet;
import java.util.stream.Collectors;
public class Test1
public static void main(String[] args)
List<User> userList = new ArrayList<>();
userList.add(new User("1","李大锤","23","南京"));
userList.add(new User("2","张无忌","18","西安"));
userList.add(new User("3","刘德华","26","苏州"));
userList.add(new User("4","郭靖","33","上海"));
userList.add(new User("1","李大锤","23","南京")); //id相同,其他数据也相同
userList.add(new User("3","带头大哥","36","杭州")); //id相同,其他数据不同
System.out.println(userList);
//根据userid去重
userList = userList.stream().collect(Collectors.collectingAndThen(Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(User :: getUserid))), ArrayList::new));
System.out.println(userList);
测试结果:
[User [userid=1, username=李大锤, age=23, address=南京], User [userid=2, username=张无忌, age=18, address=西安], User [userid=3, username=刘德华, age=26, address=苏州], User [userid=4, username=郭靖, age=33, address=上海], User [userid=1, username=李大锤, age=23, address=南京], User [userid=3, username=带头大哥, age=36, address=杭州]]
[User [userid=1, username=李大锤, age=23, address=南京], User [userid=2, username=张无忌, age=18, address=西安], User [userid=3, username=刘德华, age=26, address=苏州], User [userid=4, username=郭靖, age=33, address=上海]]
可以看出,此操作把后面的两个id相同的都给剔除了。若两个id一样,其他数据不同的话,留下的数据是靠前的数据,剔除的是靠后的数据。
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