用java实现4、短消息功能模拟模拟短消息接收和有关操作最多存储20条短消息所编写的程序应包含且不限于如下功能：1短消息接收如果短消息总数超出20条则删除最早的短消息；2短列表显示所有短消息；3阅读任意一条短消息；4删除任意一条短消息；5消除所有短消息；6具有操作功能菜单。7短消息发送

下面是一个使用Java实现短消息功能模拟的例子：

import java.util.ArrayList;
import java.util.Date;
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;
    }
}

class MessageManager {
    private ArrayList<Message> messages;

    public MessageManager() {
        this.messages = new ArrayList<>();
    }

    public void receiveMessage(String content) {
        if (messages.size() >= 20) {
            messages.remove(0);
        }
        messages.add(new Message(content));
    }

    public void displayMessages() {
        for (int i = 0; i < messages.size(); i++) {
            Message message = messages.get(i);
            System.out.println("Message " + (i + 1) + ": " + message.getContent() + " [" + message.getTimestamp() + "]");
        }
    }

    public void readMessage(int index) {
        if (index >= 1 && index <= messages.size()) {
            Message message = messages.get(index - 1);
            System.out.println("Message " + index + ": " + message.getContent() + " [" + message.getTimestamp() + "]");
        } else {
            System.out.println("Invalid message index!");
        }
    }

    public void deleteMessage(int index) {
        if (index >= 1 && index <= messages.size()) {
            messages.remove(index - 1);
            System.out.println("Message " + index + " deleted.");
        } else {
            System.out.println("Invalid message index!");
        }
    }

    public void deleteAllMessages() {
        messages.clear();
        System.out.println("All messages deleted.");
    }
}

public class Main {
    public static void main(String[] args) {
        MessageManager manager = new MessageManager();
        Scanner scanner = new Scanner(System.in);

        while (true) {
            System.out.println("1. Receive message");
            System.out.println("2. Display messages");
            System.out.println("3. Read message");
            System.out.println("4. Delete message");
            System.out.println("5. Delete all messages");
            System.out.println("0. Exit");
            System.out.print("Enter your choice: ");
            int choice = scanner.nextInt();

            switch (choice) {
                case 1:
                    System.out.print("Enter message content: ");
                    scanner.nextLine(); // Consume the newline character
                    String content = scanner.nextLine();
                    manager.receiveMessage(content);
                    System.out.println("Message received.");
                    break;
                case 2:
                    manager.displayMessages();
                    break;
                case 3:
                    System.out.print("Enter message index to read: ");
                    int readIndex = scanner.nextInt();
                    manager.readMessage(readIndex);
                    break;
                case 4:
                    System.out.print("Enter message index to delete: ");
                    int deleteIndex = scanner.nextInt();
                    manager.deleteMessage(deleteIndex);
                    break;
                case 5:
                    manager.deleteAllMessages();
                    break;
                case 0:
                    System.out.println("Exiting program...");
                    System.exit(0);
                default:
                    System.out.println("Invalid choice!");
            }

            System.out.println();
        }
    }
}

这个程序使用了一个Message类来表示短消息，其中包含消息内容和时间戳。MessageManager类负责管理短消息，包括接收、显示、阅读和删除等操作。在Main类中，使用一个无限循环来处理用户的操作选择