I've explored interactive programming and malleable code principles for a long time, and I've always felt that this kind of tool was missing in the Java ecosystem. I think this will be useful to the Java community for presentations, experimentation, talks, learning, data viz apps and small back office apps.
You can try a few apps in your browser in the playground: https://javelit.io/playground (note this is not compatible with Safari).
Under the hood the project is a bit different from Streamlit, as it is possible to integrate Javelit apps in existing Java systems. There are 2 main ways to run and build Javelit: "standalone", as a CLI, with a great hot-reload experience and a single click deploy with railway, or "embedded", as a library in an existing system. The API to build custom components is also simpler, as there is no difference between official components and user components.
If you are curious about my build process, I maintain a dev log here: https://world.hey.com/cdecatheu/