在Java中發送帶附件的郵件可以使用JavaMail API來實現。以下是一個示例代碼：

import java.util.Properties;
import javax.mail.Authenticator;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;
import javax.activation.DataHandler;
import javax.activation.DataSource;
import javax.activation.FileDataSource;

public class EmailSender {
    public static void main(String[] args) {
        // 發件人郵箱和密碼
        final String username = "your_email@example.com";
        final String password = "your_password";

        // 發件人郵箱的 SMTP 服務器地址
        final String smtpHost = "smtp.example.com";

        // 收件人郵箱
        String toEmail = "recipient@example.com";

        // 創建郵件會話
        Properties props = new Properties();
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.host", smtpHost);
        props.put("mail.smtp.port", "587");
        props.put("mail.smtp.starttls.enable", "true");

        Session session = Session.getInstance(props, new Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(username, password);
            }
        });

        try {
            // 創建郵件消息
            Message message = new MimeMessage(session);
            message.setFrom(new InternetAddress(username));
            message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(toEmail));
            message.setSubject("JavaMail Attachment Example");

            // 創建郵件內容
            MimeMultipart multipart = new MimeMultipart();
            MimeBodyPart messageBodyPart = new MimeBodyPart();
            messageBodyPart.setText("This is a sample email with attachment.");

            // 附件文件路徑
            String attachmentPath = "/path/to/attachment.txt";
            // 創建附件
            MimeBodyPart attachmentBodyPart = new MimeBodyPart();
            DataSource source = new FileDataSource(attachmentPath);
            attachmentBodyPart.setDataHandler(new DataHandler(source));
            attachmentBodyPart.setFileName(source.getName());

            // 將內容和附件添加到郵件中
            multipart.addBodyPart(messageBodyPart);
            multipart.addBodyPart(attachmentBodyPart);
            message.setContent(multipart);

            // 發送郵件
            Transport.send(message);
            System.out.println("Email sent successfully.");
        } catch (MessagingException e) {
            e.printStackTrace();
        }
    }
}

在上述代碼中，你需要替換以下內容：

• your_email@example.com：發件人郵箱
• your_password：發件人郵箱密碼
• smtp.example.com：發件人郵箱的 SMTP 服務器地址
• recipient@example.com：收件人郵箱
• /path/to/attachment.txt：附件的文件路徑

確保你已經添加了javax.mail和activation依賴，以及正確配置了郵件服務器信息。