UserList.java

import java.util.ArrayList;
import java.util.UUID;

public class UserList {
    private ArrayList<User> users;
    private static UserList userList;

    private UserList() {
        users = DataLoader.loadUsers();
    }

    public static UserList getInstance() {
        if (userList == null) {
            userList = new UserList();
        }
        return userList;
    }

    public boolean addUser(User user) {
        if (user == null) {
            return false;
        } else {
            users.add(user);
            saveUsers();
        }
        return false;
    }

    public boolean haveUser(LoginInfo info) {
        for (User user : users) {
            if (user.getUserLogin().getUserName().equals(info.getUserName())
                    && user.getUserLogin().getPassword().equals(info.getPassword())) {
                return true;
            }
        }
        return false;
    }

    public User getUserByUUID(UUID uuid) {
        for (User u : users) {
            if (u.getUUID().equals(uuid))
                return u;
        }
        return null;
    }

    public User getUserByUserName(String userName) {
        for (User u : users) {
            if (u.getUserLogin().getUserName().equals(userName))
                return u;
        }
        return null;
    }

    public ArrayList<User> getUsers() {
        return users;
    }

    public void saveUsers() {
        DataWriter.saveUsers();
    }
}