Question

我正在使用blueJ来写这个。我想要做的是在userGroup类中编写一个名为removeUser（）的方法，该方法将String作为参数，这是我想要删除的用户名。使用迭代器迭代列表，直到找到具有该用户名的用户并将其删除。我的代码是：

package user; 
public class User{
    public enum UserType{                          
        ADMIN, EDITOR, USER;
    }

    private String id;                            
    private UserType userPermissions;              
    private String actualName;                     

    public User(String username, UserType userType, String name){
        id = username;
        userPermissions = userType;
        actualName= name;
    }

    public String getUsername(){
        return id;
    }

    public UserType getUserType(){
        return userPermissions;
    }       

    public String getName(){
        return actualName;
    }

    public void setUserType(UserType input){
        userPermissions = input;
    }
}

，userGroup类为：

package user;
import java.util.*;
import user.User.UserType; 

public class UserGroup{

    private ArrayList<User> people;

    public UserGroup(){
        people = new ArrayList<User>();
    }

    public void addSampleData(){
        people.add(new User("jar1g13", UserType.ADMIN,"Jonny"));
        people.add(new User("ao9", UserType.EDITOR,"Aniruddh"));
        people.add(new User("pe6", UserType.USER,"Peter"));
        people.add(new User("mat73", UserType.USER,"Matthew"));
        people.add(new User("ora69", UserType.EDITOR,"Oranthi"));
        people.add(new User("ben12", UserType.USER,"Benedict"));
        people.add(new User("cam30", UserType.ADMIN,"Cambyse"));
        people.add(new User("are20", UserType.USER,"Alex"));
        people.add(new User("lim19", UserType.USER,"Liam"));
        people.add(new User("ada13", UserType.EDITOR,"Adam"));
    } 

    public User getUser(int idx){
        return people.get(idx);
    }

    public void printUsernames(){
        for (User user: people){
            System.out.printf("%s %s\n", user.getUsername(), user.getUserType());
        }
    }

    public void removeFirstUser(){
        people.remove(0);
    }

    public void removeLastUser(){
        people.remove(people.size()-1);
    }

    public void removeUser(String username){
        people.remove(username);
    }

}

这一切都很好编译，但是当我运行removeUser方法时，它似乎没有从数组中删除任何内容！

Answer 1

public void removeUser(String username) {
     Iterator<User> itr = people.iterator();
     while (itr.hasNext()) {
          Users element = (User) itr.next();
          if (element.getUsername().equals(username)) {
               itr.remove(); // REMOVE THIS FROM Iterator
          }
     }
}

Answer 2

尝试删除用户而不是带有字符串username的节点，或者如果您确实想要通过字符串删除用户，只需迭代直到找到具有相同字符串的用户，User.actualName.equals（username）

public void removeUser(String username) {
   Iterator<User> it = people.iterator();
   while(it.hasNext()) {
   if(it.next().getName().equals(username)) { it.remove(); break; }
   }
}

Answer 3

您想要创建一个功能。说，getUserByName(String name);

如此：

public User getUserByName(String name){
    for(int i = 0 ; i < people.size(); i++){
        if(people.get(i).actualName.equals(name)){
            return people.get(i);
        }
    }
}

然后您只需执行以下操作即可将其删除：

people.remove(getUserByName("Alex"));

Answer 4

我建议使用Map，其中key是昵称。然后删除看起来像

Map<String,User>myMap = new HashMap<String,User>();
myMap.put("username", new User(...)); 
myMap.remove("username")

这种方法提供了更好的性能，因为读取Map比迭代Array更有效，并且它在代码中看起来更好

Answer 5

这是一个线索：

public void removeUser(String username){
    people.remove(username);
}

这里，username是一个字符串。您正在尝试从仅包含Users而不包含字符串的ArrayList中删除String。

Answer 6

public int addProduct(Product item)

{  

    int id = 0;

    stock.add(item);

    numberOfProducts++;

    for(int i = 0 ; i < stock.size(); i++)
    {

        if(stock.get(i).getID() == item.getID())
        {

           id++;

        }

        if(id > 1)

        {

            stock.remove(i);

            numberOfProducts--;

        }

    }

    return id;

}

这对于修复具有相同ID的产品或商品非常有用！如果您对var名称搜索项目分配“BlueJ”等级12有任何疑问。

通过用户名从arraylist中删除用户

6 个答案: