How multi-threading can be used in a real time web based application, can i get some scenarios

Question

How multi-threading can be used in a real time web based application, can i get some scenarios.

I am learning Java Multi threading concept, i have worked on java web application.

But never got a chance to work on multi threading, just wanted to know for what kind of operations it can be used.

Answer 1

For example, you are working with an order system. A user might have multiple orders, an order from eBay, another from Amazon. And you need return his/her orders by his id.

You can get his orders with a single thread:

List<Order> getOrders(String userId) {
    getEBayOrders(userId);
    getAmazonOrders(urderId);
}

if getEBayOrders takes 1 second, getAmazonOrders takes 1 second, then you need 2 seconds to return the result.

With 2 threads, you can call getEBayOrders and getAmazonOrders at the same time, then the user can get his orders in 1 second.