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LaunchDarkly SDK for Java

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Supported Java versions

This version of the LaunchDarkly SDK works with Java 7 and above.

Quick setup

  1. Add the Java SDK to your project

  2. Import the LaunchDarkly package:

     import com.launchdarkly.client.*;
  3. Create a new LDClient with your SDK key:

     LDClient ldClient = new LDClient("YOUR_SDK_KEY");

Your first feature flag

  1. Create a new feature flag on your dashboard

  2. In your application code, use the feature's key to check wthether the flag is on for each user:

     LDUser user = new LDUser(username);
     boolean showFeature = ldClient.boolVariation("your.feature.key", user, false);
     if (showFeature) {
       // application code to show the feature 
     else {
       // the code to run if the feature is off


The LaunchDarkly SDK uses SLF4J. All loggers are namespaced under com.launchdarkly. For an example configuration check out the hello-java project.

Be aware of two considerations when enabling the DEBUG log level:

  1. Debug-level logs can be very verbose. It is not recommended that you turn on debug logging in high-volume environments.
  2. Potentially sensitive information is logged including LaunchDarkly users created by you in your usage of this SDK.

Learn more

Check out our documentation for in-depth instructions on configuring and using LaunchDarkly. You can also head straight to the complete reference guide for this SDK or our Javadocs.


We run integration tests for all our SDKs using a centralized test harness. This approach gives us the ability to test for consistency across SDKs, as well as test networking behavior in a long-running application. These tests cover each method in the SDK, and verify that event sending, flag evaluation, stream reconnection, and other aspects of the SDK all behave correctly.


We encourage pull-requests and other contributions from the community. We've also published an SDK contributor's guide that provides a detailed explanation of how our SDKs work.

About LaunchDarkly

  • LaunchDarkly is a continuous delivery platform that provides feature flags as a service and allows developers to iterate quickly and safely. We allow you to easily flag your features and manage them from the LaunchDarkly dashboard. With LaunchDarkly, you can:
    • Roll out a new feature to a subset of your users (like a group of users who opt-in to a beta tester group), gathering feedback and bug reports from real-world use cases.
    • Gradually roll out a feature to an increasing percentage of users, and track the effect that the feature has on key metrics (for instance, how likely is a user to complete a purchase if they have feature A versus feature B?).
    • Turn off a feature that you realize is causing performance problems in production, without needing to re-deploy, or even restart the application with a changed configuration file.
    • Grant access to certain features based on user attributes, like payment plan (eg: users on the ‘gold’ plan get access to more features than users in the ‘silver’ plan). Disable parts of your application to facilitate maintenance, without taking everything offline.
  • LaunchDarkly provides feature flag SDKs for
  • Explore LaunchDarkly