Java 模拟短消息系统：接收、显示、阅读和删除消息

import java.util.ArrayList;import java.util.Date;import java.util.List;import java.util.Scanner;class Message {private String content;private Date timestamp;public Message(String content) {this.content = content;this.timestamp = new Date();}public String getContent() {return content;}public Date getTimestamp() {return timestamp;}}public class ShortMessageSystem {private static final int MAX_MESSAGES = 20;private List<Message> messages;public ShortMessageSystem() {messages = new ArrayList<>();}public void receiveMessage(String content) {if (messages.size() >= MAX_MESSAGES) {messages.remove(0);}Message message = new Message(content);messages.add(message);}public void displayMessages() {if (messages.isEmpty()) {System.out.println("No messages.");} else {for (int i = 0; i < messages.size(); i++) {Message message = messages.get(i);System.out.println("[" + i + "] " + message.getContent());}}}public void readMessage(int index) {if (index >= 0 && index < messages.size()) {Message message = messages.get(index);System.out.println("Message content: " + message.getContent());System.out.println("Received at: " + message.getTimestamp());} else {System.out.println("Invalid message index.");}}public void deleteMessage(int index) {if (index >= 0 && index < messages.size()) {messages.remove(index);System.out.println("Message deleted.");} else {System.out.println("Invalid message index.");}}public void deleteAllMessages() {messages.clear();System.out.println("All messages deleted.");}public static void main(String[] args) {Scanner scanner = new Scanner(System.in);ShortMessageSystem sms = new ShortMessageSystem();while (true) {System.out.println("Short Message System");System.out.println("1. Receive a message");System.out.println("2. Display all messages");System.out.println("3. Read a message");System.out.println("4. Delete a message");System.out.println("5. Delete all messages");System.out.println("6. Exit");System.out.print("Enter your choice: ");int choice = scanner.nextInt();scanner.nextLine(); // Consume newline characterswitch (choice) {case 1:System.out.print("Enter message content: ");String content = scanner.nextLine();sms.receiveMessage(content);System.out.println("Message received.");break;case 2:sms.displayMessages();break;case 3:System.out.print("Enter message index: ");int index = scanner.nextInt();scanner.nextLine(); // Consume newline charactersms.readMessage(index);break;case 4:System.out.print("Enter message index: ");int deleteIndex = scanner.nextInt();scanner.nextLine(); // Consume newline charactersms.deleteMessage(deleteIndex);break;case 5:sms.deleteAllMessages();break;case 6:System.out.println("Exiting...");System.exit(0);default:System.out.println("Invalid choice. Please try again.");}System.out.println();}