File Channels

A FileChannel is the NIO-level way to read and write files. Where the Files API is the simple front door for everyday file work, channels are the basement: lower level, more knobs, and well-suited to raw throughput, random access, OS-level locking, or memory-mapped views into large files. This lesson covers how to open a FileChannel, how reading and writing through ByteBuffer actually works, how to position-jump around a file, how to flush data to disk, how transferTo enables zero-copy I/O, how memory-mapped files provide array-like access to multi-gigabyte data, and how file locks coordinate processes that share a file.