Envision a scenario where you need to design a chat server for thousands of concurrent connections. How would you design the server and what Java networking APIs would you use?

To efficiently handle thousands of concurrent connections in a chat server, Java NIO (Option 2) with non-blocking sockets and a selector is the preferred choice. It allows a single thread to manage multiple connections efficiently. Options 1 and 4, which use traditional multi-threading with ServerSocket or a thread pool with Socket, may lead to high resource consumption and thread management overhead. Option 3, although it uses NIO, suggests multi-threading, which is less efficient than a single-threaded NIO with a selector for such high concurrency scenarios.