The central abstractions of the NIO APIs are:
* *Buffers, which are containers for data; *
Charsets and their
* associated decoders and encoders,
which
* translate between bytes and Unicode characters;
Channels of
* various types, which represent connections
to entities
* capable of performing I/O operations; and
Selectors and selection keys, which
* together with
selectable channels define a multiplexed,
* non-blocking
I/O facility.
The {@code java.nio} package defines the buffer classes, which * are used throughout the NIO APIs. The charset API is defined in * the {@link java.nio.charset} package, and the channel and selector * APIs are defined in the {@link java.nio.channels} package. Each of * these subpackages has its own service-provider (SPI) subpackage, * the contents of which can be used to extend the platform's default * implementations or to construct alternative implementations. * * * *
| Buffers | *Description |
|---|---|
| {@link java.nio.Buffer} | *Position, limit, and capacity; * clear, flip, rewind, and mark/reset |
| * {@link java.nio.ByteBuffer} | *Get/put, compact, views; allocate, wrap |
| * {@link java.nio.MappedByteBuffer} | *A byte buffer mapped to a file |
| * {@link java.nio.CharBuffer} | *Get/put, compact; allocate, wrap |
| * {@link java.nio.DoubleBuffer} | *Get/put, compact; allocate, wrap |
| * {@link java.nio.FloatBuffer} | *Get/put, compact; allocate, wrap |
| * {@link java.nio.IntBuffer} | *Get/put, compact; allocate, wrap |
| * {@link java.nio.LongBuffer} | *Get/put, compact; allocate, wrap |
| * {@link java.nio.ShortBuffer} | *Get/put, compact; allocate, wrap |
| {@link java.nio.ByteOrder} | *Typesafe enumeration for byte orders |
A buffer is a container for a fixed amount of data of a * specific primitive type. In addition to its content a buffer has a * position, which is the index of the next element to be read * or written, and a limit, which is the index of the first * element that should not be read or written. The base {@link * java.nio.Buffer} class defines these properties as well as methods * for clearing, flipping, and rewinding, for * marking the current position, and for resetting the * position to the previous mark. * *
There is a buffer class for each non-boolean primitive type. * Each class defines a family of get and put methods * for moving data out of and in to a buffer, methods for * compacting, duplicating, and slicing a buffer, * and static methods for allocating a new buffer as well as * for wrapping an existing array into a buffer. * *
Byte buffers are distinguished in that they can be used as the * sources and targets of I/O operations. They also support several * features not found in the other buffer classes: * *
A byte buffer can be allocated as a direct buffer, in which * case the Java virtual machine will make a best effort to perform * native I/O operations directly upon it.
A byte buffer can be created by {@link * java.nio.channels.FileChannel#map mapping} a region of a * file directly into memory, in which case a few additional * file-related operations defined in the {@link * java.nio.MappedByteBuffer} class are available.
A byte buffer provides access to its content as either a * heterogeneous or homogeneous sequence of binary data of any * non-boolean primitive type, in either big-endian or little-endian * byte order.
Unless otherwise noted, passing a {@code null} argument to a * constructor or method in any class or interface in this package * will cause a {@link java.lang.NullPointerException * NullPointerException} to be thrown. * * @since 1.4 * @author Mark Reinhold * @author JSR-51 Expert Group */ package java.nio;