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• Enhancements in JDK 8 Release
• Enhancements in JDK 7 Release
• Enhancements in JDK 6 Release
• Enhancements in JDK 5.0 Release
• Enhancements in J2SDK 1.4
• Previous Enhancements

Enhancements in JDK 8 Release

There are several improvements to the standard(java.nio.charset.Charset) and extended charsetimplementations. They include:

• NewSelectorProvider implementation for Solaris based on the Solaris event port mechanism. ThisSelectorProvider may improve performance or scalability for some server workloads. The/dev/poll SelectorProvider continues to be the default. To use the Solaris event port mechanism, run with the system propertyjava.nio.channels.spi.Selector set to the valuesun.nio.ch.EventPortSelectorProvider.

• Decrease in the size of<JDK_HOME>/jre/lib/charsets.jar file

• Performance improvement for thejava.lang.String(byte[], *) constructor and thejava.lang.String.getBytes() method.

Enhancements in JDK 7 Release

Thejava.nio.filepackage and its related package,java.nio.file.attribute,provide comprehensive support for file I/O and for accessing thefile system. A zip file system provider is also available in JDK 7.The following resources provide more information:

• FileI/O (featuring NIO 2.0) in the Java Tutorials; NIO stands fornon-blocking I/O
• Developing a Custom FileSystem Provider
• Zip File SystemProvider
• The directory<Javahome>/sample/nio/chatserver/ contains samples thatdemonstrate the new APIs contained in thejava.nio.file package
• The directory<Javahome>/demo/nio/zipfs/ contains samples thatdemonstrate the NIO.2 NFS (Network File System) file system

In addition, the following enhancement is introduced:

Area: NIO
Standard/Platform: JDK 7
Synopsis: Prior to the JDK 7 release, direct buffersallocated usingjava.nio.ByteBuffer.allocateDirect(int)were aligned on a page boundary. In JDK 7, the implementation haschanged so that direct buffers are no longer page aligned. Thisshould reduce the memory requirements of applications that createlots of small buffers.
RFE:4837564

Enhancements in JDK 6 Release

java.io

One new class is provided:

• Console -Contains methods to access a character-based console device. ThereadPassword() methods disable echoing thus they aresuitable for retrieval of sensitive data such as passwords. ThemethodSystem.console()returns the unique console associated with the Java VirtualMachine.

The following new methods were added toFile:

• 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 includeschecks for write permissions and other operating systemrestrictions
• Methods to set or query file permissions:
  • setWritable(boolean writable, boolean ownerOnly) andsetWritable(booleanwritable) set the owner's or everybody's writepermission
  • setReadable(boolean readable, boolean ownerOnly) andsetReadable(booleanreadable) set the owner's or everybody's readpermission
  • setExecutable(boolean executable, boolean ownerOnly) andsetExecutable(booleanexecutable) set the owner's or everybody's executepermission
  • canExecute()tests the value of the execute permission

Constructors were added to the following class:

• IOExceptionsupports exception chaining via the addition of the newconstructorsIOException(String, Throwable) andIOException(Throwable).

The behavior of the following method was modified:

• TheFile.isFile()Windows implementation has been modified to always returnfalse for reserved device names such as CON, NUL, AUX,LPT, etc. Previously it returnedtrue, which customersconsidered a bug because it was inconsistent with behavior fordevices on UNIX.

java.nio

• A newjava.nio.channels.SelectorProviderimplementation that is based on the Linux epoll event notificationfacility is included. The epoll facility is available in the Linux2.6, and newer, kernels. The new epoll-basedSelectorProvider implementation is more scalable thanthe traditional poll-basedSelectorProviderimplementation when there are thousands ofSelectableChannelsregistered with aSelector.The newSelectorProvider implementation will be usedby default when the 2.6 kernel is detected. The poll-basedSelectorProvider will be used when a pre-2.6 kernel isdetected.
• The system propertysun.nio.ch.disableSystemWideOverlappingFileLockCheckcontrols whetherjava.nio.channels.FileChannel.lock()checks whether regions are locked by other instances ofFileChannel. Unless this system property is set totrue,FileChannel.lock() will throw anOverlappingFileLockException if an application attemptsto lock a region that overlaps one that is locked by anotherinstance ofFileChannel. The system property exists toprovide compatibility with previous releases which do not implementthe JVM-wide overlapping file lock check.

Enhancements in JDK 5.0Release

java.nio

• Classjavax.net.ssl.SSLEnginewas added. The existing J2SDK 1.4.0 secure communicationinfrastructure,javax.net.ssl.SSLSocket,was based on the I/O model of java.net.Socket. TheSSLEngine class abstracts away the I/O model, andleaves developers free to secure communication pathways usingalternate types of I/O.SSLEngine can be combined withthe New I/O APIs to create implementations such as secure blockingor non-blockingSocketChannels. For details see theJSSE ReferenceGuide.

Enhancements in Java SE 1.4

java.io

• In theFileInputStreamandFileOutputStreamclasses,getChannel methods have been added to returnthe underlyingFileChannel object, and theclose methods have been revised to close theunderlying channel.
• Similarly, in theRandomAccessFileclass, agetChannel method has been added and theclose method has been revised to close the underlyingchannel. TheRandomAccessFile constructors now supportthe mode characters"s" and"d" to allow thespecification, at file-open time, of synchronous writes orsynchronous-data writes.
• In theInputStreamReaderandOutputStreamWriterclasses, constructors have been added that take a stream and aCharset object, and thegetEncodingmethods have been revised to return the historical name of theencoding being used. Constructors toInputStreamReaderandOutputStreamWriter have been added that takeexistingCharsetDecoder andCharsetEncoder objects, respectively.

java.nio

• The nio packages were added to supplement the I/O facilitiesprovided the java.io package.
• Three new functions were added to the Java Native Interface(JNI) to support direct buffers:NewDirectByteBuffer,GetDirectBufferAddress, andGetDirectBufferCapacity.

Previous Enhancements

• Features of java.io.File describeschanges to thejava.io.File class.
• Other changes describes modificationsmade to thejava.io package.
• Character Streams discusses very earlychanges to the java.io class package to support characterstreams.