java.nio.channels · java.base · since Java 1.4

FileChannel

declaration

public abstract class FileChannel extends AbstractInterruptibleChannel
        implements SeekableByteChannel, GatheringByteChannel, ScatteringByteChannel

Block-oriented file access: positional (thread-safe) reads/writes, memory mapping, locking, and zero-copy transferTo — the substrate of high-performance file I/O.

Key methods

`static FileChannel open(Path, OpenOption...)`	READ/WRITE/CREATE/APPEND options.
`int read(ByteBuffer dst, long position)`	Positional read — no seek, thread-safe.
`MappedByteBuffer map(MapMode, long pos, long size)`	Memory-map a region.
`long transferTo(long pos, long count, WritableByteChannel)`	Zero-copy file → socket.
`FileLock lock()`	Advisory cross-process file locking.