如何使用GMail,Yahoo或Hotmail通过Java应用程序发送电子邮件？

import javax.mail.*;
import javax.mail.internet.*;
import java.util.Properties;

public void sendEmail(String to, String subject, String body) {
    // 设置邮件服务器的主要属性
    Properties props = new Properties();
    props.put("mail.smtp.auth", "true");
    props.put("mail.smtp.starttls.enable", "true");
    props.put("mail.smtp.host", "smtp.gmail.com");
    props.put("mail.smtp.port", "587");

    // 获取邮件服务器的认证信息
    String username = "your_email@gmail.com";
    String password = "your_email_password";

    // 创建一个身份验证对象
    Authenticator auth = new Authenticator() {
        protected PasswordAuthentication getPasswordAuthentication() {
            return new PasswordAuthentication(username, password);
        }
    };

    // 创建一个邮件会话对象
    Session session = Session.getInstance(props, auth);

    try {
        // 创建一个消息对象
        Message message = new MimeMessage(session);

        // 设置发件人、收件人、主题和正文
        message.setFrom(new InternetAddress(username));
        message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(to));
        message.setSubject(subject);
        message.setText(body);

        // 发送消息
        Transport.send(message);

        System.out.println("Email sent successfully!");

    } catch (MessagingException e) {
        e.printStackTrace();
    }
}

sendEmail("recipient@example.com", "Hello", "This is a test email.");