匹配 List 中的 id 并获取字符串 - Java

Question

我必须获取 UserName -> firstname 和 lastname，其中 ID 与 UserIN 列表相匹配。

我不知道该怎么做，我认为 for 循环不好，我们可以通过 Collecions 来避免不好的实现。

有什么解决办法吗？

用户输入 class:

public class UserIN {
    int id;
    UserName name;


    @Override
    public String toString() {
        return "UserIN{" +
                "id=" + id +
                ", name=" + name +
                '}';
    }

    public UserIN(int id, UserName name) {
        this.id = id;
        this.name = name;
    }
    // getters & setters here
}

用户名class:

public class UserName {
    String firstname;
    String lastname;

    @Override
    public String toString() {
        return "UserName{" +
                "firstname='" + firstname + '\'' +
                ", lastname='" + lastname + '\'' +
                '}';
    }

    public String getFirstname() {
        return firstname;
    }

    public void setFirstname(String firstname) {
        this.firstname = firstname;
    }

    public String getLastname() {
        return lastname;
    }

    public void setLastname(String lastname) {
        this.lastname = lastname;
    }

    public UserName() {}

    public UserName(String firstname, String lastname) {
        this.firstname = firstname;
        this.lastname = lastname;
    }
}

Answer 1

如果你想避免循环，你可以使用Map

import java.util.*;

...

// Maps user ids (integer) to UserName objects:
Map<Integer, UserName> map = new HashMap<>();

// Create two users and put them in the map:
UserIN user0 = new UserIN(0, new UserName("Peter", "Woodbridge"));
UserIN user1 = new UserIN(1, new UserName("Anne", "Miller"));
map.put(user0.id, user0.name);
map.put(user1.id, user1.name);

// Get user with id==1 from the map and print it to standard output
UserName user = map.get(1);
System.out.println(user.firstname + " " + user.lastname);

这会打印：

Anne Miller

匹配 List 中的 id 并获取字符串 - Java

Match the id from List and get the String - Java

java

collections

object

hashmap