Java in a Nutshell, 5th Edition

I/O and Networking with java.nio

Java 1.4 introduced an entirely new API for high-performance, nonblocking I/O and networking. This API consists primarily of three new packages. java.nio defines Buffer classes that are used to store sequences of bytes or other primitive values. java.nio.channels defines channels through which data can be transferred between a buffer and a data source or sink, such as a file or a network socket. This package also contains important classes used for nonblocking I/O. Finally, the java.nio.charset package contains classes for efficiently converting buffers of bytes into buffers of characters. The sections that follow contain examples of using all three of these packages as well as examples of specific I/O tasks with the New I/O API.

Basic Buffer Operations

The java.nio package includes an abstract Buffer class, which defines generic operations on buffers. This package also defines type-specific subclasses such as ByteBuffer, CharBuffer, and IntBuffer. (See Buffer and ByteBuffer in the reference section for details on these classes and their various methods.) The following code illustrates typical sequences of buffer operations on a ByteBuffer. The other type-specific buffer classes have similar methods.

import java.nio.*; // Buffers don't have public constructors. They are allocated instead. ByteBuffer b = ByteBuffer.allocate(4096); // Create a buffer for 4,096 bytes // Or do this to try to get an efficient buffer from the low-level OS ByteBuffer ...