根据输入的数量在while循环中创建多个java线程

Question

i am trying to write a java programm that is reading informations out of a database and creates for every row of the table a new thread. So i dont know how much threads i will need. so far i have this:

        con = DriverManager.getConnection(url, user, passwd);
        pst = con.prepareStatement("select hostname, ipadress, vncpassword from infoscreens");
        rs = pst.executeQuery();
        int i=0;
        while (rs.next()) {
            i++;
            Thread tread[i]  = new Savescreenshots(rs.getString(1),rs.getString(3),rs.getString(2));
            tread[i].start();
        }

but the problem is that this isnt working. i need a possibility to create for each row in the table a new thread. dose anyone have an idea how to do that

thanks and greetings

Answer 1

You need a dynamically growing container for a set of unknown size - a List , for example:

List<Thread> threads = new ArrayList<Thread>();
while (rs.next()) {
    Thread tread  = new Savescreenshots(rs.getString(1),rs.getString(3),rs.getString(2));
    tread.start();
    threads.add(thread);
}

At this point, all Thread objects that your program created and started are elements of the threads list. You can enumerate them and do whatever else you were planning to do with them (eg wait for them to finish):

for (Thread thread : threads) {
    thread.join();
}

Answer 2

您的想法听起来很疯狂，但您可以做的是使用Java中的SQL功能，找出您当前有多少行，然后使用该数字创建您的线程。

Answer 3

try using just simple variable say t instead of array tread[i].

Also, creating a new thread for every row might fill out memory if number of rows is large.