Question

Here’s my code

public class Main {

private static class GetData implements Runnable{

    private List list;
    private SqlQuery query;
    GetData(SqlQuery<String> param){
        this.query=param;
    }

    public void run(){


        list = query.execute();

    }

}


public static void main(String[] args){

    ApplicationContext context = new      ClassPathXmlApplicationContext("database.xml");
    SqlQuery<String> parameter =  (SqlQuery<String>) context.getBean("BEAN_NAME");

    System.out.println("hello");


    new Thread(new Inner(parameter)).start();


   for(each element in list of inner class){

       System.out.println(element.id);
   }

}

}

Well my question is after i get the query from xml file, it executes but it doesnt print anything? Why?

Also, how do i ensure that after all my threads have finished execution, only then my main program moves ahead in execution, given i make another thread and run it to create another list.

Answer 1

Change

new Thread(new Inner(parameter)).start();

to

Thread t = new Thread(new Inner(parameter));
t.start();

and put t.join(); after your for loop.

EDIT:
For 5 or any number of threads say n

Create an array of threads like this

Thread[] tArray = new Thread[n];

for (int j = 0; j < tArray .length; j++) {

//your code to start the thread goes here

}

Once you have started them all, loop through them again at the end of the main function to join each of them to main thread.

for (int j = 0; j < tarray .length; j++) {

tArray.join()

}