java overview and java se6

7/31/2019 Java Overview and Java Se6

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Java Overview andJava SE 6 What's New

Max LiCampus Ambassador in HKUST

Gigi LiCampus Ambassador in CUHK

Sun Microsystems, Inc.


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All About


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What's the meaning of

?? Andy Bechtolsheim Vinod Khosla Scott McNealy Bill Joy


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What is

doing ??


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Product ofSun

Computer servers and workstations(based on Sun's SPARC, AMD's Opteron, Intel's Xeon)

Storage systems(Sun StorageTek 5800 System, Sun Fire X4500 storage server,SAM-QFS filesystem)

Operating System(Solaris OS)

Developer tools(Netbeans, Sun Studio)

Platform& Standards(Java, Java SE, Java EE, Java ME)

Database Management Systems(JavaDB, PostgreSQL for Solaris, MySQL)

Others(Sunspot, Systems Management, Mozilla Suite, Identity Manageretc.)


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Campus AmbassadorProgram

Towards

Education


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Sun Academic Initiative Program

Take the online course of Sun technologies for FREE!

based on 2 websites:http://learningconnection.sun.comhttp://sunsite.scut.edu.cn

Nearly 60% discount for the Sun Certificate !!! SCJP: Sun Certified Java Programmer

SCSA: Sun Certified System Administration for the Solaris Operating SystemSun Certified Developer for Sun Application ServerSun Certified Engineer for Sun Directory Server


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share the most to the world !


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November 13rd. 2006


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http://mustang.dev.java.net


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CommunitySun Developer Community of China

http://developers.sun.com.cn

Open Technology Community http://www.opentech.org.cn

NetBeans Community http://www.netbeans.org

OpenSolaris Community http://www.opensolaris.org

Java Community http://www.java.net

OpenJDK Community

http://community.java.net/OpenJDK
http://developers.sun.com.cn/http://www.opentech.org.cn/http://www.netbeans.org/http://www.opensolaris.org/http://www.java.net/http://community.java.net/OpenJDKhttp://community.java.net/OpenJDKhttp://www.java.net/http://www.opensolaris.org/http://www.netbeans.org/http://www.opentech.org.cn/http://developers.sun.com.cn/


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Java and NetbeansJava and NetbeansOverviewOverview


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What is Java?


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Java is a Brand!Compatibility is Guaranteed!


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Java is a Programming Language!


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Java is a Platform!


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Where is Java?


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Java is Everywhere

NASAs Mars ExplorationRovers

NASA's Mars Exploration Rovers


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Java is FREE Software


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Java is being used by everyone

Printers

TVs

Webcams

STBs

Cash Registers

PDAs

Telescopes

Medical Equipment

Lottery Terminals

Consumer Electronics

Game Consoles

Robots


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Java Dominates in Financial Services

Source: Forresters Architect Survey on European Financial Industry in Jan 2008

http://www.sun.com/aboutsun/media/analyst/european_fsa.pdf


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Java Community


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Java.net: The Source for Java TechnologyCollaboration

What it is:> Web-based community for Java

developers

> Open, collaborative Java

development> Communities with commoninterests (java gaming)

Active and vibrant> 175,000+ members

> 2,200+ projects> 19 Java communities

> 74 hosted JUGs

> 100 RSS feeds

> Blogs, Wikis, Javapedia


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Mark Your Calendar!

San Francisco: May 6-9, 2008


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NetBeans


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What Is NetBeans?

There are two answers...

#1: It is an award-winning IDE For Java developers (but we're adding more

languages...)

Free, open-source - http://www.netbeans.org

Large (and growing) community of users that canhelp.
http://www.netbeans.org/http://www.netbeans.org/


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What Is NetBeans?

#2: It is a Platform

For building rich client applications that willrun on anyoperating system that supportsa standard JVM.

Provides a rich framework of windows,

menus, tool bars, actions, etc. Used for building a wide variety of

applications


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What Is NetBeans?

Seeing isbelieving

Quick Examples

> Minex


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What makes NetBeans the best?

1. Ant Based Project System

2. Friendly Editor

3. Powerful J2EE Support4. Visual J2ME Development

5. An integrated Profiler

6. Collaboration tools


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What makes NetBeans the best?

(cont.)7. Spectacular GUI Builder (Project

Matisse)

8. Refactoring support9. CVS support

10. Java BluePrints Solution Catalog

11. Module Development Support

12. Update Center


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What's New In NetBeans 6.0?

Code editor enhancements

Ruby, JRuby, & Ruby on Rails support

Easier installation and upgrading

Swing GUI data binding Integrated profiling, profiling points

Integrated visual web features

Mobility graphical game builder

SOA & UML enhancements

Netbeans platform enhancements


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Netbeans 6.0 Resources

Netbeans Product Site: http://www.netbeans.org> Download: previews, current & past releases of IDE, plugins

> Learning: tutorials, technical articles, flash demos

> Community: latest news, forums, events, mailing lists

Netbeans Wiki: http://wiki.netbeans.org/wiki/> Open-source documentation site for Netbeans

Planet Netbeans: http://www.planetnetbeans.org/

> Aggregate for all Netbeans-related blogs

Source Code: cvs.netbeans.org:/cvs> CVS source code access for Netbeans platform + IDE
http://www.netbeans.org/http://wiki.netbeans.org/wiki/http://www.planetnetbeans.org/http://cvs.netbeans.org/cvshttp://cvs.netbeans.org/cvshttp://www.planetnetbeans.org/http://wiki.netbeans.org/wiki/http://www.netbeans.org/


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=Opportunity

Go Get It !


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Hello World

The Scene BehindProgramming with Java


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Hello World

public class HelloWorld {public static void main( String[] arg ) {System.out.println( "Hello World" );

}

}


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Compile Hello World

Compile


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Compile ...

HelloWorld.java HelloWorld.classCompiler


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javac and g++ ??

compile to binarybytecode

resolve all referenceas symbolichandles

memory layout isdefined uponexecution

compile to binarymachine code

resolve all pointersinto memory address

memory layout is

defined by compiler

javac g++


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class System

public final class System {

public final static InputStream in = nullInputStream();

public final static PrintStream out = nullPrintStream();}

System.out.println( "Hello World" );

Handle toPrintStream

object


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Problem with Pointers

Fragile Super-class Problem

Security Problem


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Fragile Super-class Problem

Before

After

Although there is no change

in the impl. of B,B is still needed to re-compile


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Security Problem

invoke theHack_Class

routine


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The Hack Class Output

Memory

layout ofclass A

re-constructprivate

variable

Modify theprivate

constant


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Run "Hello World"

Run


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Run...

HelloWorld.class

Verifier Interpreter

JVM

Class Loader


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Class Loader

Local File SystemClass Namespace

Network-loadedClass Namespace

JVM

HelloWorld.class WorldWideWeb.class


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Verifier

Verify the executing Bytecode comesfrom different compiler

No forging pointers No violating access restrictions

No object is accessed with invalid type


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The Entire Process


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How to manage memory without pointer in Java?

Why need manage memory?

How & Why?


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Execute ...

public class HelloWorld {public static void main( String[] arg ) {System.out.println( "Hello World" );

}

}String instance

PrintStreamMethod


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class String

public final class String {

private final char value[];private final int offset;private final int count;

private int hash;}

Read-only

immutable obj


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Hello World Modified

public class HelloWorld {public static void main( String[] arg ) {System.out.println( "Hello World" + "~" );

}

}What's

happening?


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class String

public final class String {

public String concat( String str ) {int otherLen = str.length();if ( otherLen == 0 ) {

return this;}char buf[] = new char[ count + otherLen ];getChars( 0, count, buf, 0 );

str.getChars( 0, otherLen, buf, count );return new String( 0, count + otherLen, buf );

}}

return new

String,where isthe oldone?


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Where is the old String?

Un-referenced ... becomes memory leak?

Deallocated immediately?

Threw into the Trash?

Trash


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The Garbage Collector

Problem of Explicit malloc() and free()1. Dangling reference2. Memory leak

GC automatically allocate memory and deallocatememory

Responsibility:

1. Allocating memory2. Ensuring referenced object in memory3. Recovering memory no longer in use


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Simple GC

class ReferenceCounter {public:

static void NewReference( Object *obj ) {

++obj->reference_count;

}

static void ThrowAway( Object *obj ) {

--obj->reference_count;

if ( obj->reference_count == 0 ) {

free( obj );

}

}

};


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GC Design Choice

Serial vs Parallel

Concurrent vs Stop-the-World

Compact vs Non-compact vs Copying

Tradeoff

Time

Heap Space GC Frequency


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GC Design in JVM

JVMConventional Garbage Collection

Pre-HotSpot:

Post-HotSpot: Exact JVM (JVM 1.2.2)Exact Garbage Collection

JVM 1.3

Generational Garbage Collection


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Generation Collection

Heap

Young Generation

Old Generation


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The Philosophy

Most object dies young

Objects survived in several rounds of GC

are important Large objects are mostly important

Few references from older to younger

objects exist


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Object dies Young??

public int Search( Vector vector, String value ) {

Iterator iter = vector.iterator();

for( int i = 0; iter.hasNext(); ++i ) {

if ( iter.next() == value ) {

return i;

}

}

return -1;

}


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Generation Characteristic

High garbagedensity

Occupy small heap

space Carry frequent GC

Low garbagedensity

Occupy big heap

space Carry few GC

Young Generation

(Minor Collection)

Old Generation

(Major Collection)


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How it works?? (young -> old)


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Java Hotspot Generations

Young generation

Old generation

Permanent generation

(e.g. Class, Method objects)

Eden

From ToSurvivor

Big Heap


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Hotspot Collectors

Serial Collector

Parallel Collector

Parallel Compacting Collector

Concurrent Mark-sweep Collector


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Serial Collector young generation


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mark-sweep-compact

slide

Serial Collector old generation


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Parallel Collector young generation


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Parallel Compacting Collector old generation

Mark phase

live objects are marked in parallel

Summary phase

calculate density and find the region worth to compact

dense prefix

dense prefix

Compaction phase

compaction is not carried in the dense prefix

Conc rrent Mark S eep Collector


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Concurrent Mark-Sweep Collector old generation


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Concurrent Mark-Sweep Collector


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Hotspot Collectors

Serial Collector-XX:+UseSerialGC

Parallel Collector

-XX:+UseParallelGC Parallel Compacting Collector

-XX:+UseParallelOldGC

Concurrent Mark-sweep Collector-XX:+UseConcMarkSweepGC


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Java Past, Now, and Future

The Evolution Process


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Java SE Timeline


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History

1995 (1.0) The First Public Release

1997 (1.1) Nested Class AddedSupport for Function Objects

2001 (1.4) Assertions AddedSupport for Verifying Codes


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Java SE 5 Language Features

Autoboxing and unboxing

Enhanced for loop

Static importTypesafe enumerations

Variable argument list

Generics Annotations (metadata)

http://java.sun.com/j2se/1.5.0/docs/relnotes/features.html#lang
http://java.sun.com/j2se/1.5.0/docs/relnotes/features.html#langhttp://java.sun.com/j2se/1.5.0/docs/relnotes/features.html#lang


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Sample Code

int sum = 0;

List list = Arrays.asList(1, 2, 3);

for (int i: list)

sum += i;

System.out.println(sum = + sum);

Generics

Auto-boxing

For-loop


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Generics

New code> Example 1

> Example 2

List list = new LinkedList();

list.add("hello world");

String msg = list.iterator().next();

public void print(Hashtable list) {

for (String key: list.keySet())System.out.println(key + =

+ list.get(key));

}


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Autoboxing of Primitive Types

Old code

New Code

ArrayList list = new ArrayList();

list.add(0, new Integer(42));

int total = ((Integer)list.get(0)).intValue();

ArrayList list =

new ArrayList();

list.add(0, 42);

int total = list.get(0);


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Enhanced for Loop

Old code

New code

Iterator iter = hashSet.iterator();

while (iter.hasNext()) {

Object obj = iter.next();

...

}

for (Object obj: hashSet) {

...

}


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Variable Argument List

Old code

New code

public void printArgs(String[] args) {

...

public void printArgs(String... args) {

for (String a: args)

System.out.println(a);

printArgs(x, y);

printArgs(x, y, z);


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Java SE 6 Top 10 Feature

Web Services Scripting

Database

More Desktop APIs Monitoring Management

Compiler Access

Pluggable Annotations

Desktop Deployment

Security

The -lities: Quality, Compatibility, Stability

http://java.sun.com/developer/technicalArticles/J2SE/Desktop/javase6/beta2.html#top10
http://java.sun.com/developer/technicalArticles/J2SE/Desktop/javase6/beta2.html#top10http://java.sun.com/developer/technicalArticles/J2SE/Desktop/javase6/beta2.html#top10


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Java Object Header

Mark Word (32/64bits)

Class Metadata Address (32/64bits)

Array Length (32//64bits)

2 words for Object, 3 words for Arrays

M k W d


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Mark Word

Li ht W i ht L ki


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Light Weight Locking-unlocked

Thread stack

Execution Stack

Method Activation

Lock Record

hash + age | 01

Object Header

Light Weight Locking


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Light Weight Locking-locked

Thread stack

Execution Stack

Method Activation

hash + age | 01

Stack Pointer

Object Header

DisplacedMark Word

CAS



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Light Weight Locking-contented

Memory

Mutex

OR

Condition Variable

Mutex Pointer

Object Header



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Light Weight Locking-recursed

Thread stack

Execution Stack

Method Activation

hash + age | 01

Stack Pointer

Object Header

CAS

recursion count

Ob ti


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Observation

Most lockings are not only uncontended,but performed repeatedly by the samethread

>> Make it cheap for a single thread toreacquire a lock can be an optimization

Bi d L ki


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Biased Locking

ObjectHeader

CAS

Light

WeightLocking

Wh t h h R k ?


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What happens when Revoke?

Fallback to light weight locking

Need to wait for Global Safepoint

( No bytecode is executing )Thread stack is walked and lock record is

enumerated

Update Object Header when object islocked

Revoking ...


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Revoking ...

Thread stack

Execution Stack

Method Activation

Displaced Mark

Stack Pointer

Object Header

walk

Update

Comparing the Lockings


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Comparing the Lockings


lock (CAS)

:

unlock (CAS)

lock (CAS)

:

unlock (CAS)

Biased Locking

lock (CAS)

:

unlock (TAB)

lock (TAB)

:

unlock (TAB)

Execution


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JavaSE 7


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Where Are We?


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Where Are We?

JDK 5 2004/9/30

JDK 6 2006/12/11JDK 72008/H2

Future?


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Future?

Source : Forrestor's Architect Survey on European Financial Industry in Jan 2008

http://www.sun.com/aboutsun/media/analyst/european_fsa.pdf
http://www.sun.com/aboutsun/media/analyst/european_fsa.pdfhttp://www.sun.com/aboutsun/media/analyst/european_fsa.pdf


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Further Readingshttp://openjdk.java.net/

http://java.sun.com/docs/white/langenv/http://java.sun.com/j2se/reference/whitepapers/memorymanagement_whitepaper.pdf

http://java.sun.com/j2se/1.5.0/docs/relnotes/features.html#lang

http://java.sun.com/developer/technicalArticles/J2SE/Desktop/javase6/beta2.html#top10

http://java.sun.com/performance/reference/whitepapers/6_performance.html
http://openjdk.java.net/http://java.sun.com/docs/white/langenv/http://java.sun.com/j2se/reference/whitepapers/memorymanagement_whitepaper.pdfhttp://java.sun.com/j2se/1.5.0/docs/relnotes/features.html#langhttp://java.sun.com/developer/technicalArticles/J2SE/Desktop/javase6/beta2.html#top10http://java.sun.com/performance/reference/whitepapers/6_performance.htmlhttp://java.sun.com/performance/reference/whitepapers/6_performance.htmlhttp://java.sun.com/developer/technicalArticles/J2SE/Desktop/javase6/beta2.html#top10http://java.sun.com/j2se/1.5.0/docs/relnotes/features.html#langhttp://java.sun.com/j2se/reference/whitepapers/memorymanagement_whitepaper.pdfhttp://java.sun.com/docs/white/langenv/http://openjdk.java.net/


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Q & A

java overview and java se6

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