I/O & NIO

Interacting with files, sockets, and byte streams is fundamental to any server-side Java application. The classic java.io package uses streams and decorator patterns. NIO.2 (Java 7+) replaced it with Path, Files, and channels for scalable, non-blocking I/O. Serialization is important to know — but mostly to understand why it should be avoided in modern code.

What You'll Find Here

Notes are being added. Planned topics:

Topic	Description
File I/O Basics	FileInputStream/FileOutputStream, BufferedReader/BufferedWriter.
NIO.2 (Java 7+)	Path, Files utility, Files.walk, WatchService.
I/O Streams	InputStream/OutputStream hierarchy; decorator pattern; try-with-resources.
Channels & Buffers	NIO Channel, ByteBuffer; key concepts for understanding reactive I/O.
Serialization	Serializable, transient, serialVersionUID; why JSON/Protobuf are preferred.

Learning Path

1. File I/O Basics — understand the classic stream model even if you'll mostly use NIO.2.
2. NIO.2 — Files.readAllLines, Files.write, and Files.walk are the day-to-day APIs.
3. I/O Streams — the decorator pattern (wrapping streams) is tested conceptually in interviews.
4. Serialization — understand the security risks and why it's avoided; know serialVersionUID.

Related Domains

• Core Java — try-with-resources from exceptions and basic type handling underpin I/O.
• Multithreading & Concurrency — NIO non-blocking channels are critical for understanding async I/O in Netty and Reactor.
• Spring Data — file storage and streaming in Spring builds on NIO.2.