And, the third and most crucial part includes containers like Docker and Kubernetes, CI/CD tools like Jenkins and TeamCity, and Infrastructure automation tools like Ansible.

Out of these Docker is the most important because it makes it easy to set up your development environment as well as it also makes the Deployment of Java Microservices easier.

Kubernetes is a next-level tool and not really needed for all JAva developers, particularly if you are not in DevOps and managing things like scaling and deployment but it's good to know from a knowledge perspective.

I suggest having good knowledge of Docker and basic knowledge of Kubernetes for Java developers and if you need resources, I recommend Maximillian SchwaurzMuller’s Docker & Kubernetes: The Practical Guide course on Udemy. You can learn both of these tools in one course.