Multi threaded programs in Java

I am about to write my first multi threaded Java application. The task basically is to create sales report for a set of products; the products and the inputs to the report generator class are completely independent.

I believe we can create multiple threads (I would like to control the number of threads to create from a properties files based on number of CPUs in the target machine). to use them generate reports asynchronously. Currently this is what I do in my single threaded program.

I wish Java gurus give me some inputs on the design. Thanks in advance.

Structure of Report Generator class
public class SalesReportGenerator { //Variables public Report prepareReport(Product prod){ //Implementation } //Helper methods used by SalesReportGenerator.prepareReport }

My current implementation which I would like to perform in a multi threaded approach.
public class ReportCreater { public static void main(String args[]){ ListProducts listProd = new ListProducts(); //Getting product list ArrayList products = listProd.getProductAsArrayList(); //To store list of products ArrayList reports = new ArrayList(); //To store reports SalesReportGenerator salesGen = new SalesReportGenerator(); Report tempReport = null; for (int i;i<products.size() ;i++ ) { tempReport = salesGen.prepareReport(products.get(i)); reports.add(tempReport); } //At this point I will have reports for all the producst //which I can use for processing, further reporting/saving. } }

I would like to know what is the best way to first create a set of threads and make them pick a product and generate report.

Thanks.

Firstly you’ll want to create a class the implements the interface Runnable. Your new object that implements the interface Runnable could take the ArrayList of products, then in the implemented method run() you could create a new instance of SalesReportGenerator and start generating your report.

So for each time a request comes in for a report you create a new thread passing in via the constructor an instance of your new object that implements Runnable and then start the thread.

This is the basics but with this and a little research on Threads you should be able to get this going.

Hope it helps.

Use Executor Framework for Threading. Search in google.