For more than 25 years, Java has played an essential role in building enterprise applications. The traditional approach of deploying more or less monolithic applications on application servers is completely challenged in the cloud, especially with Serverless and Lambda functions. During this presentation, we will see the main paradigm differences as well as the challenges of this new approach: with among others the invocation and execution model, the development model (what about the usual frameworks), how to package and deploy, cold starts and optimizations, use cases...