Aditya61101/LLD_Java ? reverse-engineered prompt

Build me a Java project that acts like a clean learning playground for OOPS, SOLID principles, design patterns, and a few low level design problems.

I want it to be easy to open in an IDE and run, with simple example code that shows each concept in a practical way, not just theory. Please organize it so each topic has its own small package or section, with clear class names and comments that explain what is happening. For the design patterns, include a few common ones like factory, singleton, strategy, observer, and decorator, with tiny demo code showing when you would use each one.

For the low level design part, add a couple of real world examples like parking lot, elevator, or chess style problems, but keep them simple and readable. Use plain Java and make sure the project builds cleanly with Maven. If you need to check current best practices or pattern examples online, go ahead.