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J2SE(TM) 5.0 New Features - JDK 5 Documentation v1.5.0, Java 2 SDK 英文文档

Java

New Features and Enhancements
J2SE 5.0

 Contents

Java 2 Platform Standard Edition 5.0 is a major feature release. The features listed below are introduced in 5.0 since the previous major release (1.4.0).

For highlights of the new features, also see J2SETM 5.0 in a Nutshell. For issues, see JDK 5.0 release notes.

Performance Enhancements
Java Language Features
Generics
Enhanced for Loop
Autoboxing/Unboxing
Typesafe Enums
Varargs
Static Import
Metadata (Annotations)
Virtual Machine
Class Data Sharing
Garbage Collector Ergonomics
Server-Class Machine Detection
Thread Priority Changes
Fatal Error Handling
High-Precision Timing Support
Base Libraries
Lang and Util Packages
Networking
Security
Internationalization
Improved Support for Environment Variables
ProcessBuilder
Formatter
Scanner
Reflection
JavaBeansTM Component Architecture
Collections Framework
Java API for XML Processing (JAXP)
Bit Manipulation Operations
Math
Instrumentation
Serialization
Concurrency Utilities
Threads
Monitoring and Management
Integration Libraries
Remote Method Invocation (RMI)
Java Database Connectivity (JDBC)
CORBA, Java IDL, and Java RMI-IIOP
Java Naming and Directory InterfaceTM (JNDI)
User Interface
Internationalization
Java Sound Technology
Java 2DTM Technology
Image I/O
AWT
Swing
Deployment
General Deployment
Java Web Start
Tools and Tool Architecture
Java Virtual Machine Tool Interface (JVMTI)
Java Platform Debugger Architecture (JPDA)
Java Compiler (javac)
Javadoc Tool
Annotation Processing Tool (apt)
Java TM 2 Platform, Standard Edition 5.0 Trouble-Shooting and Diagnostic Guide
OS & Hardware Platforms
Supported System Configurations
64-Bit AMD Opteron Processors

Performance Enhancements

For a synopsis of performance enhancements, see Performance Enhancements.

JavaTM Language Features

For more information see New Language Features.

Generics

This long-awaited enhancement to the type system allows a type or method to operate on objects of various types while providing compile-time type safety. It adds compile-time type safety to the Collections Framework and eliminates the drudgery of casting. Refer to JSR 14.

Enhanced for Loop

This new language construct eliminates the drudgery and error-proneness of iterators and index variables when iterating over collections and arrays. Refer to JSR 201 .

Autoboxing/Unboxing

This facility eliminates the drudgery of manual conversion between primitive types (such as int) and wrapper types (such as Integer). Refer to JSR 201 .

Typesafe Enums

This flexible object-oriented enumerated type facility allows you to create enumerated types with arbitrary methods and fields. It provides all the benefits of the Typesafe Enum pattern ("Effective Java," Item 21) without the verbosity and the error-proneness. Refer to JSR 201.

Varargs

This facility eliminates the need for manually boxing up argument lists into an array when invoking methods that accept variable-length argument lists. Refer to JSR 201.

Static Import

This facility lets you avoid qualifying static members with class names without the shortcomings of the "Constant Interface antipattern." Refer to JSR 201.

Metadata (Annotations)

This language feature lets you avoid writing boilerplate code under many circumstances by enabling tools to generate it from annotations in the source code. This leads to a "declarative" programming style where the programmer says what should be done and tools emit the code to do it. Also it eliminates the need for maintaining "side files" that must be kept up to date with changes in source files. Instead the information can be maintained in the source file. Refer to JSR 175.

Virtual Machine

Class Data Sharing

The class data sharing feature is aimed at reducing application startup time and footprint. The installation process loads a set of classes from the system jar file into a private, internal representation, then dumps that representation to a "shared archive" file. During subsequent JVM invocations, the shared archive is memory-mapped in, saving the cost of loading those classes and allowing much of the JVM's metadata for these classes to be shared among multiple JVM processes. For more information, click the above link.

Garbage Collector Ergonomics

The parallel collector has been enhanced to monitor and adapt to the memory needs of the application. You can specify performance goals for applications and the JVM will tune the size of the Java heap to meet those performance goals with the smallest application footprint consistent with those goals. The goal of this adaptive policy is to eliminate the need to tune command-line options to achieve the best performance. For a synopsis of garbage collection features, click the above link.

Server-Class Machine Detection

At application startup, the launcher can attempt to detect whether the application is running on a "server-class" machine.

Thread Priority Changes

Thread priority mapping has changed somewhat allowing Java threads and native threads that do not have explicitly set priorities to compete on an equal footing.

Fatal Error Handling

The fatal error reporting mechanism has been enhanced to provide improved diagnostic output and reliability.

High-Precision Timing Support

The method System.nanoTime() has been added, providing access to a nanosecond-granularity time source for relative time measurements. The actual precision of the time values returned by System.nanoTime() is platform-dependent.

Base Libraries

Lang and Util Packages

For a synopsis of java.lang and java.util enhancements, click the above link.

Networking

For a synopsis of added networking features, click the above link.

Security

This release of J2SE offers significant enhancements for security. It provides better support for security tokens, support for more security standards (SASL, OCSP, TSP), improvements for scalability (SSLEngine) and performance, plus many enhancements in the crypto and Java GSS areas. For details see the above link.

Internationalization

Enhancements are as follows:
  • Character handling is now based on version 4.0 of the Unicode standard. This affects the Character and String classes in the java.lang package, the collation and bidirectional text analysis functionality in the java.text package, character classes in the java.util.regex package, and many other parts of the J2SE. As part of this upgrade, support for supplementary characters has been specified by the JSR 204 expert group and implemented throughout the J2SE. See the article Supplementary Characters in the Java Platform, the Java Specification Request 204, and the Character class documentation for more information.
  • The DecimalFormat class has been enhanced to format and parse BigDecimal and BigInteger values without loss of precision. Formatting of such values is enhanced automatically; parsing into BigDecimal needs to be enabled using the setParseBigDecimal method.
  • Vietnamese is now supported in all locale sensitive functionality in the java.util and java.text packages. See the Supported Locales document for complete information on supported locales and writing systems.

Improved Support for Environment Variables

The System.getenv(String) method is no longer deprecated. The new System.getenv() method allows access to the process environment as a Map<String,String>.

ProcessBuilder

The new ProcessBuilder class provides a more convenient way to invoke subprocesses than does Runtime.exec. In particular, ProcessBuilder makes it easy to start a subprocess with a modified process environment (that is, one based on the parent's process environment, but with a few changes).

Formatter

An interpreter for printf-style format strings, the Formatter class provides support for layout justification and alignment, common formats for numeric, string, and date/time data, and locale-specific output. Common Java types such as byte, java.math.BigDecimal , and java.util.Calendar are supported. Limited formatting customization for arbitrary user types is provided through the java.util.Formattable interface.

Scanner

The java.util.Scanner class can be used to convert text into primitives or Strings. Since it is based on the java.util.regex package, it also offers a way to conduct regular expression based searches on streams, file data, strings, or implementors of the Readable interface.

Reflection

Have added support for generics, annotations, enums and have added convenience methods. Also have generified the class java.lang.Class.

JavaBeans Component Architecture

A subclass of PropertyChangeEvent called IndexedPropertyChangeEvent has been added to support bound properties that use an index to identify the part of the bean that changed. Also, methods have been added to the PropertyChangeSupport class to support firing indexed property change events.

Collections Framework

The Collections Framework has been enhanced in the following ways:
  • Three new language features are targeted at collections: Generics, Enhanced for Loop, and Autoboxing.
  • Three new interfaces have been added to the framework (two of which are part of java.util.concurrent): Queue, BlockingQueue, and ConcurrentMap.
  • Two concrete implementations of Queue have been added, as well as one skeletal implementation.
  • Five blocking queue implementations have been added, and one ConcurrentMap implementation.
  • Special-purpose Map and Set implementations are provided for use with typesafe enums.
  • Special-purpose copy-on-write List and Set implementations have been added.
  • Wrapper implementations are provided to add dynamic type-safety for most collection interfaces.
  • Several new algorithms are provided for manipulating collections.
  • Methods are provided to compute hash codes and string representations for arrays.

Java API for XML Processing (JAXP)

Click the above link for details or refer to JSR 206.

Bit Manipulation Operations

The wrapper classes (Integer, Long, Short, Byte, and Char) now support common bit manipulation operations which include highestOneBit, lowestOneBit, numberOfLeadingZeros, numberOfTrailingZeros, bitCount, rotateLeft, rotateRight, reverse, signum, and reverseBytes.

Math

The numerical functionality provided by the libraries has been augmented in several ways:
  • The BigDecimal class has added support for fixed-precision floating-point computation. Refer to JSR 13.
  • The Math and StrictMath libraries include hyperbolic transcendental functions (sinh, cosh, tanh), cube root, base 10 logarithm, etc.
  • Hexadecimal floating-point support - To allow precise and predictable specification of particular floating-point values, hexadecimal notation can be used for floating-point literals and for string to floating-point conversion methods in Float and Double.

Instrumentation

The new java.lang.instrument package provides services that allow Java programming agents to instrument programs running on the Java virtual machine. The intrumentation mechanism is modification of the bytecodes of methods.

Serialization

Support has been added to handle enumerated types which are new in version 5.0. The rules for serializing an enum instance differ from those for serializing an "ordinary" serializable object: the serialized form of an enum instance consists only of its enum constant name, along with information identifying its base enum type. Deserialization behavior differs as well--the class information is used to find the appropriate enum class, and the Enum.valueOf method is called with that class and the received constant name in order to obtain the enum constant to return.

Concurrency Utilities

The java.util.concurrent, java.util.concurrent.atomic, and java.util.concurrent.locks packages provide a powerful, extensible framework of high-performance, scalable, thread-safe building blocks for developing concurrent classes and applications, including thread pools, thread-safe collections, semaphores, a task scheduling framework, task synchronization utilities, atomic variables, and locks. The addition of these packages to the core class library frees the programmer from the need to craft these utilities by hand, in much the same manner that the Collections Framework did for data structures. Additionally, these packages provide low-level primitives for advanced concurrent programming which take advantage of concurrency support provided by the processor, enabling programmers to implement high-performance, highly scalable concurrent algorithms in the Java language to a degree not previously possible without resorting to native code. Refer to JSR 166 .

Threads

The java.lang.Thread class has the following enhancements:
  • Thread priority handling has changed; see the above link for details.
  • Thread.State enum class and the new getState() API are provided for querying the execution state of a thread.
  • The new thread dump API - the getStackTrace and getAllStackTraces methods in the Thread class - provides a programmatic way to obtain the stack trace of a thread or all threads.
  • The uncaughtExceptionHandler mechanism, previously available only through the ThreadGroup class, is now available directly through the Thread class.
  • A new form of the sleep() method is provided which allows for sleep times smaller than one millisecond.

Monitoring and Management

This release of J2SE offers significant enhancements for monitoring and management for the Java platform. See the above link for details.
  • Monitoring and management API for the Java virtual machine
    The new java.lang.management package provides the interface for monitoring and managing the Java virtual machine.
  • Monitoring and management API for the logging facility
    The new java.util.logging.LoggingMXBean interface is the management interface for the logging facility.
  • JMX instrumentation of the Java virtual machine
    The Java virtual machine (JVM) has built-in instrumentation that enables you to monitor and manage it using JMX. You can easily start a JMX agent for monitoring and managing remote or local Java VMs instrumentation or of any application with JMX instrumentation. See Monitoring and Management Using JMX for details.
  • The SNMP agent publishes the standard MIB for the Java virtual machine instrumentation as defined by JSR 163. For more information, see SNMP Monitoring and Management.
  • JavaTM Management Extensions
    JMXTM API version 1.2 and the RMI connector of the JMX Remote API version 1.0 are included in J2SE 5 release. The JMX API allows you to instrument libraries and applications for monitoring and management. The RMI connector allows this instrumentation to be remotely accessible. See the JMX documentation for more details.

Integration Libraries

Remote Method Invocation (RMI)

RMI has been enhanced in the following areas:
  • Dynamic Generation of Stub Classes - This release adds support for the dynamic generation of stub classes at runtime, obviating the need to use the Java Remote Method Invocation (Java RMI) stub compiler, rmic, to pregenerate stub classes for remote objects. Note that rmic must still be used to pregenerate stub classes for remote objects that need to support clients running on earlier versions.
  • Standard SSL/TLS Socket Factory Classes - This release adds standard Java RMI socket factory classes, javax.rmi.ssl.SslRMIClientSocketFactory and javax.rmi.ssl.SslRMIServerSocketFactory, which communicate over the Secure Sockets Layer (SSL) or Transport Layer Security (TLS) protocols using the Java Secure Socket Extension (JSSE).
  • Launching rmid or a Java RMI Server from inetd/xinetd - A new feature, provided by the System.inheritedChannel method, allows an application to obtain a channel (java.nio.channels.SocketChannel or java.nio.channels.ServerSocketChannel, for example) inherited from the process that launched the virtual machine (VM). Such an inherited channel can be used to either service a single incoming connection (as with SocketChannel) or accept multiple incoming connections (as with ServerSocketChannel). Therefore, Java networking applications launched by inetd (Solaris(tm) Operating System) or xinetd (Linux) can now obtain the SocketChannel or ServerSocketChannel inherited from inetd/xinetd.

Java Database Connectivity (JDBC)

RowSet interface, part of the javax.sql package, introduced in J2SE version 1.4, provides a lightweight means of passing data between components.

At this release, as an aid to developers, the RowSet interface has been implemented (as JSR 114) in five of the more common ways a RowSet object can be used. These implementations provide a standard that developers are free to use as is or to extend.

Following are the five standard implementations:

  • JdbcRowSet - used to encapsulate a result set or a driver that is implemented to use JDBC technology
  • CachedRowSet - disconnects from its data source and operates independently except when it is getting data from the data source or writing modified data back to the data source. This makes it a lightweight container for as much data as it can store in memory.
  • FilteredRowSet - extends CachedRowSet and is used to get a subset of data
  • JoinRowSet - extends CachedRowSet and is used to get an SQL JOIN of data from multiple RowSet objects
  • WebRowSet - extends CachedRowSet and is used for XML data. It describes tabular components in XML using a standardized XML schema.

CORBA, Java IDL, and Java RMI-IIOP

Enhancements to CORBA, Java IDL, and Java RMI-IIOP are discussed in Changes in CORBA Features Between J2SE 1.4.x and 5.0.

Java Naming and Directory InterfaceTM (JNDI)

JNDI provides the following new features.
  • Enhancements to javax.naming.NameClassPair to access the fullname from the directory/naming service
  • Support for standard LDAP controls: Manage Referral Control, Paged Results Control and Sort Control
  • Support for manipulation of LDAP names.

User Interface

Internationalization

  • To render multilingual text, using logical fonts, 2D now takes advantage of installed host OS fonts for all supported writing systems. For example, if you run in a Thai locale environment, but have Korean fonts installed, both Thai and Korean are rendered. The J2RE now also automatically detects physical fonts that are installed into its lib/fonts/fallback directory and adds these physical fonts to all logical fonts for 2D rendering.
  • AWT now uses the Unicode APIs on Windows 2000/XP. As a result, some of its components can handle text without being restricted by Windows locale settings. For example, AWT text components can accept and display text in the Devanagari writing system regardless of the Windows locale settings.

Java Sound Technology

  • Ports are now available on all platforms (RFE 4782900).
  • MIDI device i/o is now available on all platforms (RFE's 4812168, 4782924).
  • Optimized direct audio access is implemented on all platforms (RFEs 4908240 and 4908879). It is enabled by default on systems which offer native mixing (i.e. Linux ALSA with hardware mixing, Solaris Mixer enabled, Windows DirectSound).
  • The new real-time Sequencer works with all MIDI devices and allows unlimited Transmitters (RFE 4773012).
  • The sound.properties configuration file allows choice of default devices (RFE 4776511). For details, see MidiSystem and AudioSystem for details.
  • MidiDevices can query connected Receivers and Transmitters (RFE 4931387, methods MidiDevice.getReceiver and MidiDevice.getTransmitter).
  • AudioFormat, AudioFileFormat, and MidiFileFormat now have properties that allow further description and qualification of the format (RFEs 4925767 and 4666845).
  • A set of ease-of-use methods allow easier retrieval of lines from AudioSystem (RFE 4896221).
  • The Sequencer interface is extended with loop methods, for seamless looping of specific portions of a MIDI sequence (RFE 4204105).
  • Java Sound no longer prevents the VM from exiting (bug 4735740).

Java 2DTM Technology

Added 2D features include expanded Linux and Solaris printer support, new methods for creating fonts from files and streams, and new methods related to VolatileImages and hardware acceleration of images. A number of internal changes to text rendering code greatly improve its robustness, performance, and scalability. Other performance work includes hardware-accelerated rendering using OpenGL (disabled by default).

Image I/O

The Image I/O system now has readers and writers for BMP and WBMP formats.

AWT

Version 5.0 features many AWT enhancements and bug fixes, including some that have often been requested by our customers. Most notably, the new MouseInfo class makes it possible to determine the mouse location on the desktop. New Window methods make it possible to specify the default location for a newly created window (or frame), appropriate to the platform. Another Window enhancement makes it possible to ensure that a window (or frame) is always on top. (This feature does not work for some window managers on Solaris/Linux.) In the area of data transfer, the new DropTargetDragEvent API allows the drop target to access transfer data during the drag operation.

Swing

With the 1.4.2 release we provided two new look and feels for Swing: XP and GTK. Rather than taking a break, in 5.0 we're providing two more look and feels: Synth, a skinnable look and feel, and Ocean, a new theme for Metal. Beyond look and feels, we've added printing support to JTable, which makes it trivial to get a beautiful printed copy of a JTable. Lastly, after seven years, we've made jFrame.add equivalent to jFrame.getContentPane().add().

Deployment

General Deployment

Pack200, a new hyper-compression format for JAR files defined by JSR 200, can significantly reduce the download size of JAR files used in Java Webstart applications and Java Plug-in applets.

For a synopsis of general deployment features and enhancements, click the General Deployment link above.

Java Web Start Deployment

For a synopsis of Java Web Start deployment features and enhancements, click the above link.

Tools and Tool Architecture

Java Virtual Machine Tool Interface (JVMTI)

JVMTI is a new native programming interface for use by development and monitoring tools. It provides both a way to inspect the state and to control the execution of applications running in the Java virtual machine (VM). JVMTI is intended to provide a VM interface for the full breadth of tools that need access to VM state, including but not limited to: profiling, debugging, monitoring, thread analysis, and coverage analysis tools.

JVMTI will replace the now deprecated JVMPI and JVMDI in the next major release of J2SE.

Java Platform Debugger Architecture (JPDA)

JPDA itself has many new features, described in more detail on the JPDA enhancements page.
  • A read-only subset of JDI has been defined. This subset can be used on a debuggee in which no debug code can be executed (such as a core file or a process that is hung or was not started in debug mode). The subset allows creation of JDI connectors for use in debugging such debuggees.
  • A service provider interface for connectors and transports allows debugger vendors, or even end users, to create their own JDI connectors and transports and plug them into the JPDA reference implementation. For example, a connector could be provided to use SSL to communicate between the debugger and debuggee.
  • JDI supports the new language features (generics, enums, and varargs).
  • The lowest layer of JPDA, the Java Virtual Machine Debugger Interface (JVMDI), has been deprecated and will be removed in the next major J2SE release. Replacing it is the Java Virtual Machine Tool Interface (JVMTI). This is a more general interface that allows profiling to be done as well as debugging. The current profiling interface, Java Virtual Machine Profiling Interface(JVMPI) is also deprecated and will be removed in the next major release.
  • The JPDA reference implementation includes new JDI connectors that allow corefiles and hung processes to be debugged.

Java Compiler (javac)

Compiler options include:
  • -source 1.5 - Enable 1.5 specific language features to be used in source files. (-target 1.5 is implied.)
  • -target 1.5 - Allow javac to use 1.5 specific features in the libraries and virtual machine.
  • -Xlint - Enable javac to produce warning messages about legal, but suspect and often problematic, program constructs. An example would be declaring a class that implements Serializable but does not define a serialVersionUID.
  • -d32 - Indicate a 32-bit Solaris or Linux platform.
  • -d64 - Indicate a 64-bit Solaris or Linux platform.
  • -target cldc1.0 - Generate class files suitable for use on VMs in Connected Limited Device Configuration (CLDC) version 1.0 and later. The compiler generates stack maps making the use of the preverifier unnecessary.

New Programmatic Interface

The com.sun.tools.javac.Main class provides two static methods to invoke the compiler from a program. See the man page for details.

Javadoc Tool

See What's New in Javadoc 5.0

Annotation Processing Tool (apt)

apt is a new command-line utility for annotation processing. It includes a set of reflective APIs and supporting infrastructure to process program annotations.

Java TM 2 Platform, Standard Edition 5.0 Trouble-Shooting and Diagnostic Guide

This guide provides descriptions of tools, options, and other items for use in analyzing problems. It contains suggestions about what to try before submitting a bug report and what data to collect for a report.

OS & Hardware Platforms

Supported System Configurations

For more information, click the above link.

64-Bit AMD Opteron Processors

With J2SE 5, AMD Opteron processors are supported by the server VM on Suse Linux and on Windows 2003.

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