apache/hadoop ? reverse-engineered prompt

I want to get this Hadoop repo building and running locally on my machine.

Please inspect the project, figure out the right way to set it up, and make sure I can compile it from a fresh checkout with the least amount of manual work. If there are any missing steps, environment requirements, or common gotchas, handle them or clearly tell me what I need to do. Then run through the most basic verification you can, like a quick build or a small sanity check, and fix anything that breaks along the way.

If you need current setup details or build guidance, look up the latest docs online. After that, give me a short summary of what you changed or learned, and the exact commands I should use to build it again next time.