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 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 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 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 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
{@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}
' ' {@link java.nio.FloatBuffer}
' ' {@link java.nio.IntBuffer}
' ' {@link java.nio.LongBuffer}
' ' {@link java.nio.ShortBuffer}
' ' {@link java.nio.ByteOrder}
Typesafe enumeration for byte orders
} 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.