如何避免Java中的代码重复 public static void sendMail（String[]to，String subject，String messageBody，String[]cc，String[]bcc）引发异常{ Properties props=System.getProperties（）； props.put（“mail.transport.protocol”、“smtp”）； props.put（“mail.smtp.port”，port）； props.put（“mail.smtp.starttls.enable”、“true”）； props.put（“mail.smtp.auth”，“true”）； Session Session=Session.getDefaultInstance（props）； MimeMessage msg=新MimeMessage（会话）； msg.setFrom（新的InternetAddress（from，fromname））； InternetAddress[]toAddress=新的InternetAddress[to.length]； for（int i=0；i

在本文中，我们在两种方法中使用相同的代码。 我想将公共代码放在另一个方法中。 我将尝试将该公共代码放在另一个方法中，然后我们将尝试调用该方法，但这两种方法都不起作用。 如果我们试图在两种方法中调用一个公共方法，那么它将只适用于一种方法

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请给我一些建议。

看起来您可以编写第二个方法来使用第一个方法，使用空数组：

public static void sendMail(String[] to, String subject, String messageBody, String[] cc, String[] bcc) throws Exception {
    Properties props = System.getProperties();
    props.put("mail.transport.protocol", "smtp");
    props.put("mail.smtp.port", PORT);
    props.put("mail.smtp.starttls.enable", "true");
    props.put("mail.smtp.auth", "true");
    Session session = Session.getDefaultInstance(props);
    MimeMessage msg = new MimeMessage(session);
    msg.setFrom(new InternetAddress(from, fromname));
    InternetAddress[] toAddress = new InternetAddress[to.length];
    for (int i = 0; i < to.length; i++) {
        toAddress[i] = new InternetAddress(to[i]);    
    }
    for (int i = 0; i < toAddress.length; i++) {
        msg.addRecipient(Message.RecipientType.TO, toAddress[i]);
    }
    msg.setSubject(subject);
    msg.setContent(messageBody, "text/html");
    if(cc[0] != "") {
        InternetAddress[] ccAddress = new InternetAddress[cc.length];
        for (int i = 0; i < cc.length; i++) {
            ccAddress[i] = new InternetAddress(cc[i]);
        }
        for (int i = 0; i < ccAddress.length; i++) {
            msg.addRecipient(Message.RecipientType.CC, ccAddress[i]);
        }
    }
    if(bcc[0] != "") {
        InternetAddress[] bccAddress = new InternetAddress[bcc.length];
        for (int i = 0; i < bcc.length; i++) {
            bccAddress[i] = new InternetAddress(bcc[i]);
        }
        for (int i = 0; i < bccAddress.length; i++) {
            msg.addRecipient(Message.RecipientType.BCC, bccAddress[i]);
        }
    }
    Transport transport = session.getTransport();
    try {
        System.out.println("Sending...");
        transport.connect(HOST, SMTP_USERNAME, SMTP_PASSWORD);
        transport.sendMessage(msg, msg.getAllRecipients());
        System.out.println("Email sent!");
    } catch (Exception ex) {
        System.out.println("The email was not sent.");
        System.out.println("Error message: " + ex.getMessage());
    } finally {
        transport.close();
    }
}
public static void sendMail(String[] to, String subject, String messageBody) throws Exception {
    Properties props = System.getProperties();
    props.put("mail.transport.protocol", "smtp");
    props.put("mail.smtp.port", PORT);
    props.put("mail.smtp.starttls.enable", "true");
    props.put("mail.smtp.auth", "true");
    Session session = Session.getDefaultInstance(props);
    MimeMessage msg = new MimeMessage(session);
    msg.setFrom(new InternetAddress(from, fromname));
    InternetAddress[] toAddress = new InternetAddress[to.length];
    for (int i = 0; i < to.length; i++) {
        toAddress[i] = new InternetAddress(to[i]);
    }
    for (int i = 0; i < toAddress.length; i++) {
        msg.addRecipient(Message.RecipientType.TO, toAddress[i]);
    }
    msg.setSubject(subject);
    msg.setContent(messageBody, "text/html");
    Transport transport = session.getTransport();
    try {
        System.out.println("Sending...");
        transport.connect(HOST, SMTP_USERNAME, SMTP_PASSWORD);
        transport.sendMessage(msg, msg.getAllRecipients());
        System.out.println("Email sent!");
    } catch (Exception ex) {
        System.out.println("The email was not sent.");
        System.out.println("Error message: " + ex.getMessage());
    } finally {
        transport.close();
    }
}

这将在cc和bcc数组中传入一个空字符串，以便其他方法跳过该数组

请注意，您将自己置于NullPointerException的开放状态：

public static void sendMail(String[] to, String subject, String messageBody) throws Exception {
    sendMail(to, subject, messageBody, new String[]{""}. new String[]{""});
}

这是盲目地假设cc数组至少包含一个元素。 如果要使用空数组调用该方法，或者对cc或bcc调用null，则程序将抛出异常。 在if语句中，您已经在使用cc.length，所以如果cc.length为零，则不会添加任何cc地址。 该测试的更好实现可能是：

if(cc[0] != "") { ... }

另外，我不知道为什么构建ccAddress阵列只是为了丢弃它。 这里是相同的循环，用单个ccAddress对象替换ccAddress数组

if (cc != null && cc.length > 0) {...}

if（cc！=null&&cc.length>0）{
对于（int i=0；i

您可以做的最简单的事情是实现第二个方法，这样它就可以调用第一个方法，而不会添加任何抄送或密件抄送收件人。根据您当前的代码，它可以是：

if(cc != null && cc.length > 0) {
    for (int i = 0; i < cc.length; i++) {
        InternetAddress ccAddress = new InternetAddress(cc[i]);
        msg.addRecipient(Message.RecipientType.CC, ccAddress);
    }
}

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你不必再做另一种方法。参数计数较低的方法只调用参数计数较高且值为null的方法，然后在“real”方法中进行null检查

public static void sendMail（String[]to，String subject，String messageBody，String[]cc，String[]bcc）引发异常{
Properties props=System.getProperties（）；
props.put（“mail.transport.protocol”、“smtp”）；
props.put（“mail.smtp.port”，port）；
props.put（“mail.smtp.starttls.enable”、“true”）；
props.put（“mail.smtp.auth”，“true”）；
Session Session=Session.getDefaultInstance（props）；
MimeMessage msg=新MimeMessage（会话）；
msg.setFrom（新的InternetAddress（from，fromname））；
InternetAddress[]toAddress=新的InternetAddress[to.length]；
for（int i=0；ipublic static void sendMail(String[] to, String subject, String body) {
    sendMail(to, subject, body, new Object[]{""}, new Object[]{""});
}

public static void sendMail(String[] to, String subject, String messageBody, String[] cc, String[] bcc) throws Exception {
    Properties props = System.getProperties();
    props.put("mail.transport.protocol", "smtp");
    props.put("mail.smtp.port", PORT);
    props.put("mail.smtp.starttls.enable", "true");
    props.put("mail.smtp.auth", "true");
    Session session = Session.getDefaultInstance(props);
    MimeMessage msg = new MimeMessage(session);
    msg.setFrom(new InternetAddress(from, fromname));
    InternetAddress[] toAddress = new InternetAddress[to.length];
    for (int i = 0; i < to.length; i++) {
        toAddress[i] = new InternetAddress(to[i]);    
    }
    for (int i = 0; i < toAddress.length; i++) {
        msg.addRecipient(Message.RecipientType.TO, toAddress[i]);
    }
    msg.setSubject(subject);
    msg.setContent(messageBody, "text/html");
    if(cc != null && cc[0] != "") {
        InternetAddress[] ccAddress = new InternetAddress[cc.length];
        for (int i = 0; i < cc.length; i++) {
            ccAddress[i] = new InternetAddress(cc[i]);
        }
        for (int i = 0; i < ccAddress.length; i++) {
            msg.addRecipient(Message.RecipientType.CC, ccAddress[i]);
        }
    }
    if(bcc != null && bcc[0] != "") {
        InternetAddress[] bccAddress = new InternetAddress[bcc.length];
        for (int i = 0; i < bcc.length; i++) {
            bccAddress[i] = new InternetAddress(bcc[i]);
        }
        for (int i = 0; i < bccAddress.length; i++) {
            msg.addRecipient(Message.RecipientType.BCC, bccAddress[i]);
        }
    }
    Transport transport = session.getTransport();
    try {
        System.out.println("Sending...");
        transport.connect(HOST, SMTP_USERNAME, SMTP_PASSWORD);
        transport.sendMessage(msg, msg.getAllRecipients());
        System.out.println("Email sent!");
    } catch (Exception ex) {
        System.out.println("The email was not sent.");
        System.out.println("Error message: " + ex.getMessage());
    } finally {
        transport.close();
    }
}

public static void sendMail(String[] to, String subject, String messageBody) throws Exception {
    sendMail(to, subject, messageBody, null, null);
}