求解：java兑现每隔30分钟自动发送邮件

import java.io.File;import java.util.Date;import java.util.Properties;import java.util.Vector;import javax.activation.DataHandler;import javax.activation.FileDataSource;import javax.mail.Authenticator;import javax.mail.Multipart;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.mail.internet.MimeUtility;public class SendMailTest {    public int sendMail(String host, String from, String username,            String password, String to, String subject, String content,            Vector appendFiles, boolean author) {        try {            Properties p = System.getProperties();            p.put("mail.smtp.host", host);            p.put("mail.smtp.auth", author + "");            p.put("mail.smtp.localhost", "forceview");            Session session = Session.getDefaultInstance(p,                    new PopupAuthenticator(username, password));            MimeMessage msg = new MimeMessage(session);            msg.setFrom(new InternetAddress(from));// 设置发送帐号            String[] tos = to.split(";");            InternetAddress[] sendTo = new InternetAddress[tos.length];            for (int i = 0; i < tos.length; i++) {                sendTo[i] = new InternetAddress(tos[i]);            }            msg.setRecipients(javax.mail.internet.MimeMessage.RecipientType.TO,                    sendTo);// 设置接收邮件的地址            msg.setSubject(subject, "utf-8");// 设置主题            msg.setSentDate(new Date());// 设置发送时间            Multipart mp = new MimeMultipart();            MimeBodyPart bp = new MimeBodyPart();            bp.setContent(                    "<meta http-equiv=Content-Type content=text/html; charset=utf-8>"                            + content, "text/html;charset=UTF-8");            mp.addBodyPart(bp);            MimeBodyPart fp;            String appendStrs = "";            if (appendFiles != null) {                for (int i = 0; i < appendFiles.size(); i++) {                    fp = new MimeBodyPart();                    appendStrs = appendFiles.get(i).toString();                    String[] filenames = appendStrs.split("\\|");                    if (new File(filenames[0]).exists()) {                        FileDataSource fds = new FileDataSource(filenames[0]);                        fp.setDataHandler(new DataHandler(fds));                        fp.setFileName(MimeUtility.encodeText(filenames[1]                                + fds.getName(), "utf-8", "K"));                        mp.addBodyPart(fp);                    }                }            }            msg.setContent(mp);            msg.saveChanges();            Transport transport = session.getTransport("smtp");// 设置发送端口            transport.connect(host, username, password);// 连接邮件服务器            transport.sendMessage(msg, msg.getAllRecipients());            transport.close();        } catch (Exception e) {            e.printStackTrace();            return -1;        }        return 0;    }    class PopupAuthenticator extends Authenticator {        private String username, password;        public PopupAuthenticator(String username, String password) {            this.username = username;            this.password = password;        }        public PasswordAuthentication getPasswordAuthentication() {            return new PasswordAuthentication(this.username, this.password);        }    }}