Skip to main content

Threads in Java - CountDownLatch (Part 12)

A CountDownLatch is a synchronizer which allows one thread to wait for one or more threads before starts processing.
A good application of CountDownLatch is in Java server-side applications where a thread cannot start execution before all the required services are started.

Working

CountDownLatch is initialized with a given count which is the number of threads it should wait for. This count is decremented by calling countDown() method by the threads once they are finished execution. As soon as the count reaches to zero, the waiting task starts running.

Code Example

Let us say we require three services, LoginService, DatabaseService and CloudService to be started and ready before the application can start handling requests.

Output

Cloud Service is up!
Login Service is up!
Database Service is up!
All services are up. Now the waiting thread can start execution.
Here, we can see that the main thread is waiting for all the three services to start before starting its own execution. Once all the services (threads) are started, it can perform its own execution.

Conclusion

Congratulations!! 🙋 today we discussed CountDownLatch with an example. I hope you enjoyed this post.

You can find the complete code of this project on my GitHub in this commit. Feel free to fork or open issues, if any.

I would love to hear your thoughts on this and would like have suggestions from you to make it better. 

Feel free to befriend me on FacebookTwitter or Linked In or say Hi by email.

Happy Coding 😊

Comments

Popular posts from this blog

Threads in Java - Masterclass (Part 0)

Multithreading is a way to introduce concurrency in a program. In any case, if there are parallel paths in our program (parts which do not depend on the result from another part), we can make use of multithreading.
One should exploit this feature, especially with all these multiple core machines nowadays.

Below are a few reasons why we should use multithreading -
1. Keep a process responsive There was once a time when you would print a document in MS Word and the application would freeze for an annoyingly long amount of time until the job finished. Eventually, Microsoft solved this problem by running a printing job parallel to the main thread/ GUI thread.  To be clear though, not only GUI apps but Network services have to keep an ear to the ground for new clients, dropped connections and cancellation requests. In either case, it is critical to do the heavy lifting on a secondary thread to keep the user satisfied. 2. Keep a processor busy Keeping a processor busy can be a tough task e…

Parsing XML using Retrofit

Developing our own type-safe HTTP library to interface with a REST API can be a real pain as we have to handle many aspects -
making connectionscachingretrying failed requeststhreadingresponse parsingerror handling, and more.  Retrofit, on the other hand, is a well-planned, documented and tested library that will save you a lot of precious time and headaches. In this tutorial, we are going to discuss how we can parse the XML response returned from https://timesofindia.indiatimes.com/rssfeedstopstories.cms using the Retrofit library.

To work with Retrofit, we need three classes -  Model class to map the JSON dataInterfaces which defines the possible HTTP operationsRetrofit.Builder class - Instance which uses the interface and the Builder API which allows defining the URL endpoint for the HTTP operation. Every method of the above interface represents on possible API call. The request type is specified by using appropriate annotations (GET, POST). The response is returned as a Call object…

Material design profile page in Android

Hey everyone, some days back I was working on one my personal Android project. In that project, I was supposed to create a simple profile page for a user. This profile page was supposed to show some basic details of a user.

The output of this UI will be like this -
I created the profile page using material design and in this post, I am going to discuss a step by step tutorial to create a simple yet elegant profile page. Without further ado, let's get started.
Creating a new project Click on File ➤ New Project ➤ Empty Activity and fill the necessary details. Change styles.xml fileNavigate to app\src\main\res\values\styles.xmlChange the style value from DarkActionBar to NoActionBar as below<resources><!-- Base application theme. --><stylename="AppTheme"parent="Theme.AppCompat.Light.NoActionBar"><!-- Customize your theme here. --><itemname="colorPrimary">@color/colorPrimary</item><itemname="colorPrimaryDark&qu…