Java NIO (New I/O)

Core NIO Components #

Buffers #

• Buffer: The base class for all buffers with position, limit, and capacity management
• ByteBuffer: Byte buffer implementation with direct and heap variants
• CharBuffer: Character buffer for text processing
• IntBuffer: Integer buffer implementation
• LongBuffer: Long buffer implementation
• FloatBuffer: Float buffer implementation
• DoubleBuffer: Double buffer implementation
• ShortBuffer: Short buffer implementation

Channels #

• Channel Interface: The core I/O operation interface
• FileChannel: File-based channel for random access
• SocketChannel: TCP socket channel implementation
• ServerSocketChannel: TCP server socket channel
• DatagramChannel: UDP datagram channel
• Pipe.SinkChannel: Pipe sink channel implementation
• Pipe.SourceChannel: Pipe source channel implementation

Selectors and Multiplexing #

• Selector: I/O multiplexing with select, poll, and epoll
• SelectionKey: Channel registration and event tracking
• SelectableChannel: Channel that can be multiplexed

Charsets and Encoding #

• Charset: Character encoding and decoding
• CharsetEncoder: Character to byte encoding
• CharsetDecoder: Byte to character decoding
• StandardCharsets: Predefined standard charsets

File I/O (NIO.2) #

• Path Interface: Platform-independent file path representation
• Paths Class: Factory methods for creating Path objects
• Files Class: File system operations (copy, move, delete, etc.)
• FileSystem: File system provider interface
• FileSystems: Factory for file system instances
• FileStore: File store (partition/drive) representation

File Attributes #

• BasicFileAttributes: Basic file attribute view
• DosFileAttributes: DOS/Windows specific attributes
• PosixFileAttributes: POSIX file attributes
• FileAttributeView: File attribute view interface
• FileOwnerAttributeView: File ownership attributes
• PosixFilePermission: POSIX file permissions

Asynchronous I/O #

• AsynchronousFileChannel: Async file I/O operations
• AsynchronousSocketChannel: Async TCP socket operations
• AsynchronousServerSocketChannel: Async TCP server socket
• CompletionHandler: Async operation completion callback

Memory-Mapped Files #

• MappedByteBuffer: Memory-mapped file buffer
• FileChannel.MapMode: Memory mapping modes

Utilities and Supporting Classes #

• ByteOrder: Endianness specification
• BufferOverflowException: Buffer overflow handling
• BufferUnderflowException: Buffer underflow handling
• InvalidMarkException: Invalid buffer mark handling

NIO Architecture Overview #

Application
    ↓
Buffers (ByteBuffer, CharBuffer, etc.)
    ↓
Channels (FileChannel, SocketChannel, etc.)
    ↓
Selectors (I/O Multiplexing)
    ↓
Operating System (epoll, kqueue, IOCP)

Performance Characteristics #

Key Features #

1. Non-blocking I/O: Enable high-performance, scalable network applications
2. Buffer-oriented: All I/O operations work with buffers for efficiency
3. Selector-based multiplexing: Single thread can handle thousands of connections
4. Memory mapping: Direct memory access to files for zero-copy I/O
5. Character set support: Comprehensive encoding/decoding framework
6. File system abstraction: Cross-platform file system operations

When to Use NIO #

Use NIO when:

• Building high-performance network servers
• Handling thousands of simultaneous connections
• Need non-blocking I/O operations
• Working with large files and memory mapping
• Requiring cross-platform file system operations

Use traditional I/O when:

• Simple file operations on small files
• Sequential processing of text files
• Blocking I/O is acceptable for your use case
• Working with character streams (Reader/Writer)

NIO vs Traditional I/O #