如何找到一个对象的长度

huangapple
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英文:

how to find length of an object

问题

以下是翻译好的部分：

我正在努力寻找消息对象的长度。给定的任务如下：练习模板带有一个预定义的 Message 类，可用于创建表示消息的对象。每条消息都有一个发送者和一些内容。

实现 MessagingService 类。该类必须有一个无参数的构造函数，并包含一个 Message 对象的列表。然后，向该类添加以下两个方法：

  1. public void add(Message message) - 将传递的消息作为参数添加到消息服务中，只要消息内容最多为 280 个字符。
  2. public ArrayList<Message> getMessages() - 返回添加到消息服务中的消息。

提示！您可以使用与字符串关联的 length() 方法来找出字符串的长度。

我的工作如下：

  1. import java.util.ArrayList;
  3. public class MessagingService {
  4.     ArrayList<Message> messages;
  5.     
  6.     public MessagingService(){
  7.         this.messages = new ArrayList();
  8.     }
  9.     
  10.     public void add(Message message){
  11.         if(message.length() <= 280){
  12.             messages.add(message);
  13.         }
  14.     }
  15.  
  16.     public ArrayList<Message> getMessages(){
  17.         ArrayList<Message> mess = new ArrayList();
  18.         for(Message m:messages){
  19.             mess.add(m);
  20.         }
  21.         return mess;
  22.     }
  23. }
  25. import java.util.Objects;
  27. public class Message {
  28.     private String sender;
  29.     private String content;
  31.     public Message(String sender, String content) {
  32.         this.sender = sender;
  33.         this.content = content;
  34.     }
  36.     public String getSender() {
  37.         return sender;
  38.     }
  40.     public String getContent() {
  41.         return content;
  42.     }
  44.     public String toString() {
  45.         return this.sender + ": " + this.content;
  46.     }
  48.     public int length(){
  49.         return this.content.length();
  50.     }
  52.     @Override
  53.     public boolean equals(Object obj) {
  54.         if (this == obj) {
  55.             return true;
  56.         }
  57.         if (obj == null) {
  58.             return false;
  59.         }
  60.         if (getClass() != obj.getClass()) {
  61.             return false;
  62.         }
  63.         final Message other = (Message) obj;
  64.         if (!Objects.equals(this.sender, other.sender)) {
  65.             return false;
  66.         }
  67.         if (!Objects.equals(this.content, other.content)) {
  68.             return false;
  69.         }
  70.         return true;
  71.     }
  72. }
英文:

I am struggling to find the length of a message object. The given task is as follow: The exercise template comes with a pre-defined Message class that can be used to create objects representing messages. Each message has a sender and some content.

Implement the MessagingService class. The class must have a parameterless constructor and contain a list of Message objects. After that, add the following two methods to the class:

public void add(Message message) - adds a message passed as a parameter to the messaging service as long as the message content is at most 280 characters long.
public ArrayList<Message> getMessages() - returns the messages added to the messaging service.
Tip! You can find out the length of the string using the length() method associated with the string.

What I have done is:

>
import java.util.ArrayList;

public class MessagingService {
ArrayList<Message> messages;

  1. public MessagingService(){
  2. this.messages = new ArrayList();
  3. }
  4. public void add(Message message){
  5. if(message.length() &lt;= 280){
  6. messages.add(message);
  7. }
  8. }
  9. public ArrayList&lt;Message&gt; getMessages(){
  10. ArrayList&lt;Message&gt; mess = new ArrayList();
  11. for(Message m:messages){
  12. mess.add(m);
  13. }
  14. return mess;
  15. }

}

import java.util.Objects;

public class Message {

  1. private String sender;
  2. private String content;
  3. public Message(String sender, String content) {
  4. this.sender = sender;
  5. this.content = content;
  6. }
  7. public String getSender() {
  8. return sender;
  9. }
  10. public String getContent() {
  11. return content;
  12. }
  13. public String toString() {
  14. return this.sender + &quot;: &quot; + this.content;
  15. }
  16. public int length(){
  17. return this.length();
  18. }
  19. // created using the &quot;insert code&quot; feature of NetBeans
  20. @Override
  21. public boolean equals(Object obj) {
  22. if (this == obj) {
  23. return true;
  24. }
  25. if (obj == null) {
  26. return false;
  27. }
  28. if (getClass() != obj.getClass()) {
  29. return false;
  30. }
  31. final Message other = (Message) obj;
  32. if (!Objects.equals(this.sender, other.sender)) {
  33. return false;
  34. }
  35. if (!Objects.equals(this.content, other.content)) {
  36. return false;
  37. }
  38. return true;
  39. }

}

Blockquote

答案1

得分: 1

在你的Message类内部，这是无意义的。它会抛出堆栈溢出异常：

  1. public int length(){
  2.     return this.length();
  3. }

你可能需要的是：

  1. public int length(){
  2.     return content.length();
  3. }
英文:

Inside your Message class, this is nonsense. It will throw stackoverflow exception:

  1. public int length(){
  2. return this.length();
  3. }

What you probably need here is:

  1.  public int length(){
  2. return content.length();
  3. }

huangapple
  • 本文由 发表于 2020年4月6日 17:12:04
  • 转载请务必保留本文链接：https://go.coder-hub.com/61056414.html
  • arrays
  • java
  • string
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