What should I do to prepare for a Java developer interview?

Because your experience is not described in the question, I will attempt to address it generally.

With the experiences of being on multiple interview panels and having attended several interviews at major IT companies, here are my two cents.

Java developers are concerned with more than simply Java; they are concerned with the technologies that surround Java, as well as the languages that run on Java and the JVM ecosystem.

Let me categorize it as follows:

  • Work on a project

  • If you participated on a project and claimed to have completed a task, know what decisions were made, why they were made, and what the impact was.

  • Draw block diagrams with ease and clearly communicate your ideas/project. I’ve observed numerous candidates that are unwilling to design block diagrams and assist the interview panel in understanding them.

  • Code on paper with a pen, in Google Docs, or in an IDE when your display is sharing.