# New I/O APIs

Documentation Contents

> The new I/O (NIO) APIs introduced in v 1.4 provide new features and improved performance in the areas of buffer management, scalable network and file I/O, character-set support, and regular-expression matching. The NIO APIs supplement the I/O facilities in the `java.io` package.

> ### Features

> The NIO APIs include the following features:
> - Buffers for data of primitive types
> - Character-set encoders and decoders
> - A pattern-matching facility based on Perl-style regular expressions
> - Channels, a new primitive I/O abstraction
> - A file interface that supports locks and memory mapping
> - A multiplexed, non-blocking I/O facility for writing scalable servers

> ### Examples

> - NIO Examples

> ### API References

> > Note: This document reflects the NIO APIs as of the J2SE v 1.4 FCS release. They remain the same in 1.4.1.

> New packages, classes, and interfaces:
> - `java.nio` package: Buffers, which are used throughout the NIO APIs.
> - `java.nio.channels` package: Channels and selectors.
> - `java.nio.charset` package: Character encodings.
> - `java.nio.channels.spi` package: Service-provider classes for channels.
> - `java.nio.charset.spi` package: Service-provider classes for charsets.
> - `java.util.regex` package: Classes for matching character sequences against patterns specified by regular expressions.
> - `java.lang.CharSequence` interface: The interface implemented by objects that can be passed as arguments to methods in the `java.util.regex` package. The `String`, `StringBuffer`, and `java.nio.CharBuffer` classes implement this interface.

> Note: The new `InetSocketAddress` and `SocketAddress` classes, while not strictly part of the NIO APIs, are used by them.

> Revised classes and interfaces:

> - In the `FileInputStream` and `FileOutputStream` classes, `getChannel` methods have been added to return the underlying `FileChannel` object, and the `close` methods have been revised to close the underlying channel.
> - Similarly, in the `RandomAccessFile` class, a `getChannel` method has been added and the `close` method has been revised to close the underlying channel. The `RandomAccessFile` constructors now support the mode characters `"s"` and `"d"` to allow the specification, at file-open time, of synchronous writes or synchronous-data writes.
> - In the `InputStreamReader` and `OutputStreamWriter` classes, constructors have been added that take a stream and a `Charset` object, and the `getEncoding` methods have been revised to return the historical name of the encoding being used. Constructors to `InputStreamReader` and `OutputStreamWriter` have been added that take existing `CharsetDecoder` and `CharsetEncoder` objects, respectively.
> - In the `String` class, two `split` methods are new. The `subSequence` method has been added, as required by the `CharSequence` interface that `String` now implements. Three additional methods have been added: `matches`, `replaceAll`, and `replaceFirst`.
> - In the `StringBuffer` class, the `subSequence` method has been added, as required by the `CharSequence` interface that `StringBuffer` now implements.
> - In the `Thread` class, the `interrupt` method has been revised to interrupt threads blocked in channel-I/O operations.
> - In the `DatagramSocket` class, the `receive` and `send` methods have been revised to throw a `java.nio.channels.IllegalBlockingModeException` if the socket has a channel and the channel is in non-blocking mode. The `close` method now closes the socket's channel, if it has one, and the new `getChannel` method returns the underlying channel, if any.
> - In the `ServerSocket` class, the `accept` and `implAccept` methods have been revised to throw a `java.nio.IllegalBlockingModeException` if the socket has a channel and the channel is in non-blocking mode. The `getChannel` method has been added and `close` revised, for the same reasons as in `DatagramSocket`.
> - In the `Socket` class, the `getInputStream` and `getOutputStream` methods have been revised to delegate all I/O operations to the socket's channel, if it has one. The `connect` methods have been revised to throw a `java.nio.IllegalBlockingModeException` if the socket has a channel and the channel is in non-blocking mode. The `getChannel` method has been added and `close` revised, for the same reasons as in `DatagramSocket`.

> Three new functions have been added to the Java Native Interface (JNI) to support direct buffers. For information, see JNI Enhancements in v 1.4.

> ### For More Information

> - New I/O: Additional Documentation
> - Supported Encodings
> - JSR-51: New I/O APIs for the Java Platform (Note: v 1.4 has a subset of the changes proposed in this specification request.)

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