java - ArrayList不存储值

Question

我正在创建一个邮件系统，有一个我无法弄清楚的小错误。我发布了所有类(class)，以防正在阅读的人需要它来理解任何内容，但我显然不希望人们读完所有类(class)。

出现的问题是，当我运行主程序时，我可以创建用户名，但是创建后，用户名不会被存储。

我认为错误要么出现在 main 类中，要么出现在 UserList 类中，但我就是找不到它。我在我认为错误的地方发表了评论。

抱歉，如果我的帖子太长和/或格式不正确。我会删除任何不需要的代码，只需告诉我需要删除的内容即可!

/**
 * Created by Broomhead0 on 4/11/14.
 */
import java.util.ArrayList;
public class Userlist
{

    //private User[] users; // this is an array that will store references to all users
    ArrayList<User> users;  //this is an arraylist that will store references to all users


    private int numberUsr; // this is the number of users that is currently stored in the user. Always smaller or equal to maxUser

    public Userlist()
    {

        users = new ArrayList<User>();
        numberUsr = 0;  // at start no user stored yet
    }

    // find a user in the list based on the username
    public User findUser(String username)
    {
        // iterate through the array; only iterate according to how many users are currently in the array
        for (int i = 0; i < numberUsr; i++)
        {
            // access the particular user through users.(i), then get the name,
            // and call the equals method on that name to compare it with the input username
            if (users.get(i).userName.equals(username)){
                return users.get(i);
            }

        }
        // no user found
        return null;
    }
//ERRORERRORERRORERRORERRORERRORERRORERRORERRORERRORERRORERRORERRORERRORERRORERRORERROR
    // add a user to the list; only do so if the user does not yet exist
    public void addUser(User u)
    {
        if (findUser(u.userName) != null) //if there is a match,
            System.out.println("User already exists");
        else //if there is not match
        {
           users.add(u); //add the username
        }
//ERRORERRORERRORERRORERRORERRORERRORERRORERRORERRORERRORERRORERRORERRORERRORERRORERROR

    }
}

Answer 1

添加新用户后，numberUsr 保持为 0。当您添加新用户时增加该值，或者在循环用户时更好地使用users.size()。

public User findUser(String username)
{
    // iterate through the array; only iterate according to how many users are currently in the array
    for (int i = 0; i < users.size(); i++)
    {
        // access the particular user through users.(i), then get the name,
        // and call the equals method on that name to compare it with the input username
        if (users.get(i).userName.equals(username)){
            return users.get(i);
        }

    }
    // no user found
    return null;
}