Java同步方法...未同步

Question

请看下面给我带来麻烦的方法：

public synchronized void readMail() throws MessagingException, IOException {
    Folder inbox = store.getFolder("Inbox");
    inbox.open(Folder.READ_ONLY);
    messages = inbox.getMessages();
    // System.out.println("No of Messages : " + inbox.getMessageCount());
    // System.out.println("No of Unread Messages : "
    // + inbox.getUnreadMessageCount());

    for (int i = 0; i < inbox.getUnreadMessageCount(); i++) {

        System.out
                .println("*****************************************************************************");
        System.out.println("NEW MESSAGE " + (i + 1) + ":");
        msg = messages[i];
        // System.out.println(msg.getMessageNumber());
        // Object String;
        // System.out.println(folder.getUID(msg)

        String subject = msg.getSubject();

        System.out.println("Subject: " + subject);
        System.out.println("From: " + msg.getFrom()[0]);
        System.out.println("To: " + msg.getAllRecipients()[0]);
        System.out.println("Date: " + msg.getReceivedDate());
        System.out.println("Size: " + msg.getSize());
        // System.out.println(msg.getFlags());
        // System.out.println("Body: \n"+ msg.getContent());
        // System.out.println(msg.getContentType());
    }
}

然后是run方法：

    public void run() {
    while (true) {

        try {
            readMail();
        } catch (MessagingException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }

        try {
            sleep(1000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}
}

Answer 1

您应该在两个线程都可以访问的对象上同步您的方法，因为现在您正在使用您所在的对象实例来同步，原因永远不会产生影响，因为就我对您的问题的理解而言，两个线程都只在它们的on范围内。您可以在两个线程创建时向它们传递一个简单的对象，并像下面这样重新格式化您的方法

传递要同步的对象：

public static void main(String[] args){
     Object obj = new Object();
     gmail g1 = new gmail(obj);
     gmail g2 = new gemail(obj);
     // more code
}

在gmail类中保存引用：

public class gmail extends Thread{
    private Object sharedObject;

    public gmail( Object synchronizer){
          sharedObject = synchronzier;
    }

public void readMail(){
   synchronized( sharedObject ){
       // your method code goes here
   }
}

public void readMail(){
   synchronized( this.getClass() ){
       // your method code goes here
   }
}