多线程Java Executor服务实现帮助

Question

在下面的代码中，userList会获取大量数据，这是因为发送电子邮件花费的时间太长

如何提高应用程序的速度，使50000封电子邮件发送速度更快？也许是用ExecutorService

List<String[]> userList = new ArrayList<String[]>();
void getRecords() {
    String [] props=null;
    while (rs.next()) {
    props = new String[2];
    props[0] = rs.getString("useremail");
    props[1] = rs.getString("active");
    userList.add(props);
    if (userList.size()>0) sendEmail();   
}
void sendEmail() {
    String [] user=null;
    for (int k=0; k<userList.size(); k++) { 
        user = userList.get(k);
        userEmail = user[0];         
        //send email code
    }
}

Answer 1

尝试以以下方式并行化代码：

private final int THREADS_NUM = 20;

void sendEmail() throws InterruptedException {
    ExecutorService executor = Executors.newFixedThreadPool( THREADS_NUM );
    for ( String[] user : userList ) { 
        final String userEmail = user[0];         
        executor.submit( new Runnable() {
            @Override
            public void run() {
                sendMailTo( userEmail );
            }
        } );
    }
    long timeout = ...
    TimeUnit timeunit = ...
    executor.shutdown();
    executor.awaitTermination( timeout, timeunit );
}

void sendMailTo( String userEmail ) {
// code for sending e-mail
}

另外，请注意，如果您不想头痛，方法sendMailTo必须是无状态的