拒绝在Java Swing中数组对象的重复属性条目。

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英文:

Reject duplicate attribute entry of an array of objects in java swing

问题

我尝试创建一个用于注册用户的程序，所以我创建了一个用户数组，其属性包括：Usuario（用户ID）、nombre（姓名）和contrase&#241;a（密码）。每当我创建一个新用户时，程序必须确保用户ID之前尚未注册过，如果已经注册过，程序必须拒绝用户注册，直到我输入一个不同的UserID。每个创建的对象（每个带有其属性的用户）都保存在数组的相应位置，所以我创建了一个具有以下功能的方法（int contador将计算我注册用户的次数，数组最多有10个，因此contador<10）：

  1. public void registrarUsuario(int contador){
  2.     int f = contador;
  3.     usuario = t3.getText();
  4.     nombre = t4.getText();
  5.     contrase&#241;a = t5.getText();
  7.     for(int i=0; i<users.length; i++){
  8.         if(users[i].getUsuario() == usuario){
  9.             JOptionPane.showMessageDialog(null, "El nombre de usuario ya ha sido utilizado");
  10.         }
  11.     }
  13.     if(this.t6.getText().equals(this.t5.getText())){  
  14.         Usuario user = new Usuario(usuario, nombre, contrase&#241;a);
  15.         users[contador] = user;
  16.         JOptionPane.showMessageDialog(null, "El usuario se ha registrado con exito!");   
  18.         this.t3.setText("");
  19.         this.t4.setText("");
  20.         this.t5.setText("");
  21.         this.t6.setText("");
  23.     } else {
  24.         JOptionPane.showMessageDialog(null, "ERROR: las contrase&#241;as no coididen");
  25.         this.t5.setText("");
  26.         this.t6.setText("");
  27.     }
  28. }

但是当我运行程序时，出现以下错误：

  1. Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
  2.     at proyecto1.Proyecto1.registrarUsuario(Proyecto1.java:143)

（请参见上面的第143行）

注意：我已经将您提供的代码进行了简单的翻译，但您提供的代码中存在一些 HTML 编码的内容（如&#241;表示的是特定字符）。如果需要完整的翻译，请提供正确格式的内容。

英文:

I try to make a program to register users, so I created an array of users with the attributes: Usuario (User ID), nombre (name) and contrase&#241;a (password), and everytime I create a new user the program has to ensure that the User ID hasn't registered before, if it's already registered the program must reject the user register until I put a different UserID, every Object created(every user with it's attributes) is saved in it's respective position of the array, so I create a method with these functions (int contador will count the times I register a User, the array has a maximum of 10 so contador<10):

  1. public  void registrarUsuario(int contador){
  2.          int f = contador;
  3.         usuario = t3.getText();
  4.         nombre = t4.getText();
  5.         contrase&#241;a = t5.getText();
  7.             for(int i=0; i&lt;users.length; i++){
  8. \line 43 with error if(users[i].getUsuario() == usuario){
  9.                     JOptionPane.showMessageDialog(null, &quot;El nombre de usuario ya ha sido utilizado&quot;);
  11.                 }
  12.             }
  16.                 
  17.         if(this.t6.getText().equals(this.t5.getText())){  
  18.            Usuario user = new Usuario(usuario, nombre, contrase&#241;a);
  19.            users[contador] = user;
  20.             
  21.         JOptionPane.showMessageDialog(null, &quot;El usuario se ha registrado con exito!&quot;);   
  22.         
  23.             this.t3.setText(&quot;&quot;);
  24.             this.t4.setText(&quot;&quot;);
  25.             this.t5.setText(&quot;&quot;);
  26.             this.t6.setText(&quot;&quot;);
  27.             
  28.         }else{
  29.             
  30.         JOptionPane.showMessageDialog(null, &quot;ERROR: las contrase&#241;as no coididen&quot;);
  31.             this.t5.setText(&quot;&quot;);
  32.             this.t6.setText(&quot;&quot;);
  33.             
  34.         }
  35.       
  36.     }

but when I run the program I get this error:

  1. Exception in thread &quot;AWT-EventQueue-0&quot; java.lang.NullPointerException
  2. 	at proyecto1.Proyecto1.registrarUsuario(Proyecto1.java:143)

( see above to line 143)

答案1

得分: 0

在这行代码中：

  1. for(int i=0; i&lt;users.length; i++){

你从未定义数组users - 要么是因为你忘记了this标识符，要么就是忘记定义它。

英文:

On this line of code:

  1. for(int i=0; i&lt;users.length; i++){

You never defined the array users - either because you forgot the this identifier, or simply forgot to define it.

答案2

得分: 0

我理解你想要实现的内容，但由于你没有发送所有的类，我没有完全理解你的方法。我会将我是如何解决这个问题的发送给你，如果你想的话，你可以重新发送所有的类和代码，以便我可以全面了解 拒绝在Java Swing中数组对象的重复属性条目。

我的代码：（当然，你可以编辑它，使其与用户交互，在这里我只显示了一般思路）

  1.     // 用户类
  2. package userArray;
  4. public class User {
  5. 	
  6. 	private int id;
  7. 	private String name;
  8. 	private String password; // Java中有特殊的密码类，但在这个问题中不会使用它们
  10. 	public User(int id, String name, String password) {
  11. 		super();
  12. 		this.id = id;
  13. 		this.name = name;
  14. 		this.password = password;
  15. 	}
  16. 	// 获取器和设置器 + toString()
  17. }
  19. // UsersList 类
  21. package userArray;
  23. import java.util.*;
  25. public class UsersList {
  26. 	
  27. 	ArrayList<User> users = new ArrayList<User>();
  28. 	
  29. 	// 原始函数
  30. 	public User createUser(int id, String name, String password) throws Exception {
  31. 		for(User u : this.users) {
  32. 			if(id == u.getId())
  33. 				throw new Exception("用户已存在...");
  34. 		}
  35. 		User u = new User(id, name, password);
  36. 		this.users.add(u);
  37. 		return u;
  38. 	}
  39. 	
  40. 	// 将原始函数包装在每次执行时的 try/catch 中的函数
  41. 	public User registerUser(int id, String name, String password) {
  42. 		try {
  43. 			return createUser(id, name, password);
  44. 		} catch (Exception e) {
  45. 			System.out.println("ID " + id + " 对应用户 " + name + " 已存在...");
  46. 			return null;
  47. 		}
  48. 	}
  50. 	public UsersList() {
  51. 		super();
  52. 		this.users = users;
  53. 	}
  54. 	// + toString()
  55. }
  57. // 主类
  59. package userArray;
  61. public class Main {
  63. 	public static void main(String[] args) {
  64. 		
  65. 		UsersList list = new UsersList();
  66. 		
  67. 		list.registerUser(1, "Kevin", "Kevin123");
  68. 		list.registerUser(2, "Sarah", "Sarah123");
  69. 		list.registerUser(1, "Steven", "Steven123");
  70. 		list.registerUser(3, "Stephany", "Stephany123");
  71. 		list.registerUser(3, "Alex", "Alex123");
  72. 		
  73. 		System.out.println("列表是:");
  74. 		System.out.println(list.toString());
  76. 	}
  77. }

执行结果：

ID 1 对应用户 Steven 已存在...
ID 3 对应用户 Alex 已存在...
列表是:
UsersList [users=[User [id=1, name=Kevin, password=Kevin123], User [id=2, name=Sarah, password=Sarah123], User [id=3, name=Stephany, password=Stephany123]]]

英文:

I got what you're trying to achieve but I didn't fully understand your method because you didn't send all the classes, so i'll send you how i solved it and if you want you can resend us all your classes and code to have a full view 拒绝在Java Swing中数组对象的重复属性条目。

My code: (of course you can edit it to be interactive with the user, here i'm showing the general idea only)

  1.     //User class
  2. package userArray;
  3. public class User {
  4. private int id;
  5. private String name;
  6. private String password;//there is special classes for password in java, not going to use them in this problem
  7. public User(int id, String name, String password) {
  8. super();
  9. this.id = id;
  10. this.name = name;
  11. this.password = password;
  12. }
  13. //getters and setters + toString()
  14. //UsersList class
  15. package userArray;
  16. import java.util.*;
  17. public class UsersList {
  18. ArrayList&lt;User&gt; users = new ArrayList&lt;User&gt;();
  19. //The original function
  20. public User createUser(int id, String name, String password) throws Exception {
  21. for(User u : this.users) {
  22. if(id == u.getId())
  23. throw new Exception(&quot;User already exists...&quot;);
  24. }
  25. User u = new User(id,name,password);
  26. this.users.add(u);
  27. return u;
  28. }
  29. //The function used to wrap the original function in try/catch each time executed
  30. public User registerUser(int id, String name, String password) {
  31. try {
  32. return createUser(id,name,password);
  33. } catch (Exception e) {
  34. System.out.println(&quot;ID &quot;+ id +&quot; for user &quot;+name+&quot; is for an existing user...&quot;);
  35. return null;
  36. }
  37. }
  38. public UsersList() {
  39. super();
  40. this.users = users;
  41. }
  42. // + toString()
  43. //Main class
  44. package userArray;
  45. public class Main {
  46. public static void main(String[] args) {
  47. UsersList list = new UsersList();
  48. list.registerUser(1, &quot;Kevin&quot;, &quot;Kevin123&quot;);
  49. list.registerUser(2, &quot;Sarah&quot;, &quot;Sarah123&quot;);
  50. list.registerUser(1, &quot;Steven&quot;, &quot;Steven123&quot;);
  51. list.registerUser(3, &quot;Stephany&quot;, &quot;Stephany123&quot;);
  52. list.registerUser(3, &quot;Alex&quot;, &quot;Alex123&quot;);
  53. System.out.println(&quot;The list is: &quot;);
  54. System.out.println(list.toString());
  55. }
  56. }

The execution result:

ID 1 for user Steven is for an existing user... <br>
ID 3 for user Alex is for an existing user... <br>
The list is: <br>
UsersList [users=[User [id=1, name=Kevin, password=Kevin123], User [id=2, name=Sarah, password=Sarah123], User [id=3, name=Stephany, password=Stephany123]]]

huangapple
  • 本文由 发表于 2020年9月12日 03:02:47
  • 转载请务必保留本文链接：https://go.coder-hub.com/63852890.html
  • java
  • netbeans
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