Enhancements in Java I/O






Documentation Contents

Enhancements in Java I/O



Contents





Enhancements in Java SE 6
Enhancements in J2SE 5.0
Enhancements in J2SDK 1.4
Previous Enhancements



Enhancements in Java SE 6

java.io

One new class is provided:


Console -
Contains methods to access a character-based console device. The
readPassword() methods disable echoing thus they are
suitable for retrieval of sensitive data such as passwords. The method
System.console()
returns the unique console associated with the Java Virtual Machine.


The following new methods were added to
File:


Methods to retrieve disk usage information:

getTotalSpace()
returns the size of the partition in bytes
getFreeSpace()
returns the number of unallocated bytes in the partition
getUsableSpace()
returns the number of bytes available on the partition and includes
checks for write permissions and other operating system restrictions



Methods to set or query file permissions:

setWritable(boolean
writable, boolean ownerOnly) and
setWritable(boolean
writable) set the owner's or everybody's write permission
setReadable(boolean
readable, boolean ownerOnly) and
setReadable(boolean
readable) set the owner's or everybody's read permission
setExecutable(boolean
executable, boolean ownerOnly) and
setExecutable(boolean
executable) set the owner's or everybody's execute permission
canExecute()
tests the value of the execute permission



Constructors were added to the following class:


IOException
supports exception chaining via the addition of the new constructors

IOException(String, Throwable) and

IOException(Throwable).


The behavior of the following method was modified:


The File.isFile()
Windows implementation has been modified to always return
false for reserved device names such as CON, NUL, AUX, LPT,
etc. Previously it returned true, which customers considered
a bug because it was inconsistent with behavior for devices on Unix.


java.nio



A new java.nio.channels.SelectorProvider
implementation that is based on the Linux epoll event notification
facility is included. The epoll facility is available in the Linux 2.6,
and newer, kernels. The new epoll-based SelectorProvider
implementation is more scalable than the traditional poll-based
SelectorProvider implementation when there are thousands of
SelectableChannels
registered with a Selector.
The new SelectorProvider implementation will be used by
default when the 2.6 kernel is detected. The poll-based
SelectorProvider will be used when a pre-2.6 kernel is
detected.

The system property
sun.nio.ch.disableSystemWideOverlappingFileLockCheck controls
whether java.nio.channels.FileChannel.lock()
checks whether regions are locked by other instances of
FileChannel. Unless this system property is set to
true, FileChannel.lock() will throw an
OverlappingFileLockException
if an application attempts to lock a region that overlaps one that is
locked by another instance of FileChannel. The system
property exists to provide compatibility with previous releases which do
not implement the JVM-wide overlapping file lock check.



Enhancements in J2SE 5.0

java.nio


Class javax.net.ssl.SSLEngine
was added. The existing J2SDK 1.4.0 secure communication infrastructure,
javax.net.ssl.SSLSocket,
was based on the I/O model of java.net.Socket. The SSLEngine
class abstracts away the I/O model, and leaves developers free to secure
communication pathways using alternate types of I/O.
SSLEngine can be combined with the New I/O APIs to create
implementations such as secure blocking or non-blocking
SocketChannels. For details see the
JSSE Reference Guide.


Enhancements in Java 2 SDK v1.4

java.io


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.


java.nio


The nio packages were added to supplement the I/O facilities provided the
java.io package.
Three new functions were added to the Java Native Interface (JNI) to
support direct buffers. For information, see JNI Enhancements in v 1.4.


Previous Enhancements


Features of java.io.File describes changes to
the java.io.File class.
Other changes describes modifications made to the
java.io package.
Character Streams discusses very early changes to the
java.io class package to support character streams.










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