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Java 7 – New Features. Svetlin Nakov. Bulgarian Association of Software Developers. Egyptian Java User Group (EGJUG) Cairo, 2 May 2010. www.devbg.org. About the Speaker. Svetlin Nakov 15+ years software engineering experience PhD in computer science from Sofia University

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slide1

Java 7 – New Features

Svetlin Nakov

Bulgarian Association of Software Developers

Egyptian Java User Group (EGJUG)

Cairo, 2 May 2010

www.devbg.org

about the speaker
About the Speaker
  • Svetlin Nakov
    • 15+ years software engineering experience
    • PhD in computer science from Sofia University
    • Chairman of the Bulgarian Association of Software Developers (BASD) – www.devbg.org
    • Author of 6 books about Java, .NET and software engineering
    • Web site: www.nakov.com
table of contents
Table of Contents
  • Java 7 – Introduction and Chronology
  • Dynamic Languages in JVM
  • Java Modularity – Project Jigsaw
  • Language Enhancements (Project Coin)
  • Closures for Java
  • JSR 203: NIO 2
  • Other new features:
    • Compressed 64-bit oops, Garbage-First GC, Upgraded Class-Loaders, URLClassLoader. close(), Unicode 5.1, SCTP and SDP
openjdk
OpenJDK

JDK7 is the second JDK done via the OpenJDK effort

OpenJDK is free, open-source and GPL licensed

A lot of the improvements of JDK7 are separate projects on OpenJDK

Some say that projects go under the cap of OpenJDK to avoid the cumbersome and slow JCP process

java 7 milestones
Java 7 – Milestones

Began in August 2006

First supposed to be 7 milestones

Mark Reinhold extended them to 10

Current status: M7 finished, presentation made with build89

M10 expected to finish 09.09.2010

“The last scheduled milestone cycle will be followed by a test and stabilization period of indeterminate length, after which the final release will be declared”

there s no jsr yet
There’s No JSR Yet

A Java 7 JSR is supposed to be formed

Java SE 6 was under the \'Umbrella\' JSR 270

JDK7 is in Eclipse’s low priority list because a lack of container JSR

JDK7 cannot be finalized without a JSR

There are some functionalities that also lack a JSR

While doing this presentation we used the term JSR TBD in lieu of the missing JSR

source control system
Source Control System

Official SCM is SVN, still

Note: it takes a \'while\' (e.g. one night)

Unofficial Mercurial forest repositories available since November 2007

Note: this also takes a \'while\'

>svn co https://jdk7.dev.java.net/svn/jdk7/trunk

>hg fclone http://hg.openjdk.java.net/

currently supported ides
Currently Supported IDEs

Eclipse

Both Eclipse 3.6M6 and E4 do not support JDK7’s syntax

… or I couldn’t figure it out 

Strangely enough the option is there:

Source compatibility: 1.7

NetBeans

6.9 Beta supports JDK7

Compiles successfully the M7 syntax

the da vinci machine project
The Da Vinci Machine Project

Prototype a number of extensions to the JVM

A.k.a. Multi Language Virtual Machine –http://openjdk.java.net/projects/mlvm/

Allows non-Java dynamic languages to run efficiently in the JVM

Emphasis is on general purpose extensions

Hosted on OpenJDK

  • Da Vinci: a multi-language renaissancefor the Java Virtual Machine architecture
dynamic languages in jvm1
Dynamic Languages in JVM
  • Da Vinci Machine sub-projects include:
    • Dynamic invocation
    • Continuations
    • Tail-calls
    • And interface injection
  • JSR 292: Supporting Dynamically Typed Languages on the Java Platform
    • The standard behind Da Vinci Machine
    • Natural continuation of JSR 223: Scripting for the Java Platform implemented in JDK 6
dynamic languages in jvm 2
Dynamic Languages in JVM (2)
  • New JVM instruction invokedynamic
    • Allows extremely fast dynamic method invocation through method handles
    • Will enable JRuby, Jython, Groovy and other dynamic and scripting languages to call dynamic methods natively at bytecode level
  • Method handles
    • Lightweight references to a method – java.dyn.MethodHandle
  • Anonymous classes in the JVM
dynamic languages in jvm 3
Dynamic Languages in JVM (3)
  • Autonomous methods
    • Methods that can be dynamically attached to an existing class at runtime
  • Interface injection
    • Acquiring base interfaces and method implementations at runtime
  • Continuations and stack introspection
    • Suspend / resume thread\'s execution stack
  • Tail calls and tail recursion
dynamic languages in jvm 4
Dynamic Languages in JVM (4)
  • Runtime support for closures
    • Closure is a lambda-expression bound (closed) to its environment
  • Multimethods
    • Dispatch a method overload depending on the actual arguments at runtime
  • Faster reflection and faster interface invocation based on dynamic invocation
  • Symbolic freedom for identifier names
dynamic invoke example
Dynamic Invoke – Example

staticvoid greeter(String x) {

System.out.println("Hello, " + x);

}

static MethodHandle greeterMethodHandle =

MethodHandles.lookup().findStatic(

DynamicInvocation.class, "greeter", MethodType.

methodType(void.class, String.class));

static {

Linkage.registerBootstrapMethod(

"bootstrapDynamic");

}

dynamic invoke example 2
Dynamic Invoke – Example (2)

privatestatic CallSite bootstrapDynamic(

Class caller, String name, MethodType type) {

if (type.parameterCount() == 1 && name == "hail") {

MethodHandle target = MethodHandles.

convertArguments(greeterMethodHandle, type);

CallSite site = new CallSite(caller, name, type);

site.setTarget(target);

System.out.println("Set the CallSite target to " +

greeterMethodHandle);

return site;

}

}

publicstaticvoid main(String... args) {

InvokeDynamic.hail("dynamic invocation");

}

java modularity

Java Modularity

Project Jigsaw

modularization introduction
Modularization – Introduction

The JDK and the JRE, have always been delivered as massive, indivisible artifacts

The growth of the platform has thus inevitably led to the growth of the basic JRE download

which now stands at well over 14MB

despite heroic engineering efforts such as the Pack200 class file compression format

Java Kernel and Quickstarter features do improve download time and startup time, at least for Windows users

the real solution
The Real Solution

The most promising way to improve the key metrics of

Download time

Startup time

And memory footprint

Is to attack the root problem head-on:

Divide the JDK into a set of well specified and separate, yet interdependent, modules

A side effect is that JAR format has to reworked

alan bateman it s difficult
Alan Bateman: It’s Difficult

Suppose you are using the Logging API

Logging requires NIO (for file locking)

And JMX (as loggers are managed)

JMX requires JavaBeans, JNDI, RMI and CORBA (JMX remote API mandates that the RMI connector support both JRMP and IIOP)

JNDI requires java.applet.Applet (huh?) and JavaBeans has dependencies on AWT, Swing

Not satisfied with this, JavaBeans has persistent delegates that create dependencies on JDBC and more

how to do it
How to Do It?

Modularizing the JDK requires a module system capable of supporting such an effort

It requires, in particular, a module system whose core can be implemented directly within the Java virtual machine

Modularizing is best done with a module system that’s tightly integrated with the Java language

Otherwise the compile-time module environment can differ dramatically from the run-time module environment

which module system
Which Module System?

JSR 277 proposes the JAM module system

Some of its rich, non-declarative features would be impossible to implement its core functionality directly within the JVM

Therefore Sun halted the development

JSR 294 is chartered to extend the language and JVM to support modular programming

Well received for its simplicity and its utility to existing module systems such as OSGi

which module system 2
Which Module System? (2)

OSGi

May 2007: OSGi 4.1 standardized as JSR-291

Reasonably mature, stable, and robust

Implemented within Apache Harmony JVM

Not at all integrated with the Java language

Jigsaw created to modularize JDK7

Will not be an official part of the Java SE 7 Platform Specification and might not be supported by other SE 7 implementations

status and examples
Status and Examples

Probably JSR 294 will be chosen

There are issues, JSR 294 is inactive (paused)

Not implemented yet (b89), java.lang.module

Example (may, and probably will, change)

module [email protected] provides [email protected], [email protected] {

requires [email protected], [email protected];

permits M6; // only M6 can depend on M1

}

module M;

package P;

publicclassFoo {...}

jsr 308 introduction
JSR 308 – Introduction

Java SE 6 permits annotations only on declarations

JSR 308 extends Java’s annotation system so that annotations may appear on nearly any use of a type

JSR 308 is backward-compatible and continues to permit those annotations

Two new types of annotations (target wise):

ElementType.TYPE_USE

ElementType.TYPE_PARAMETER

jsr 308 examples
JSR 308: Examples

publicstaticvoid main() {

//for generic type arguments in a generic method

JSR308Example2.<@NonNull String>method("...");

//for type parameters and type parameter bounds:

Collection<@Long ? [email protected] File> c = null;

//for class inheritance:

class UnmodifiableList<T> implements

@Readonly List<@Readonly T> { }

}

//for throws clauses:

void monitorTemperature() [email protected] Exception {}

//for method receivers:

public String toString() @Readonly { returnnull; }

// helper only

publicstatic <T> T method(String s) {returnnull;}

project coin introduction
Project Coin – Introduction

Project Coin unites all language changes to the Java Lang Specification (JLS) to be added to JDK 7

Open call for proposals

From February 27, 2009

Through March 30, 2009

70 proposal forms

9 were chosen

No Milestone selected yet (so not all features are available)

the chosen ones
The Chosen Ones

Strings in Switch

By Joseph D. Darcy

Automatic Resource Management

By Joshua Bloch

Improved Type Inference for Generic Instance Creation

By Jeremy Manson

Simplified Varargs Method Invocation

By Bob Lee

the chosen ones 2
The Chosen Ones (2)

Collection Literals

By Joshua Bloch

Indexing access syntax for Lists and Maps

By Shams Mahmood

Language support for JSR 292

By John Rose

Binary Literals

Underscores in numbers

By Derek Foster

strings in switch
Strings in Switch

Syntactic sugar

// Finally! - strings in switch

String s = "";

switch (s) {

case"Edno":

out.println("1");

break;

case"Dve":

out.println("2");

break;

default:

out.println("Unknown BG number.");

break;

}

arm the problem
ARM – The Problem

A resource is as an object that must be closed manually

InputStream, Reader, Writer, DB connection

Manual resource termination has proven ugly and error prone

Even good programmers get it wrong

Resource leaks or even outright failures, which may be silent

If an exception is thrown in the try block, and in the finally block, the second supplants the first

arm the problem 2
ARM – The Problem (2)

Where’s the problem with this code?

If an exception is thrown in the try block, and in the finally block, the second supplants the first

Was "Text" written successfully?

BufferedWriter br =

new BufferedWriter(new FileWriter(path));

try{

br.write("Text");

} finally {

br.close();

}

how it s done one resource
How It’s Done (One Resource)
  • Try-finally – with one resource:

BufferedWriter br =

new BufferedWriter(new FileWriter(path));

try{

// This exception is more important

br.write("Text");

} finally {

try {

// ... than this one

br.close();

} catch(IOException ioe) {}

}

how it s done two resources
How It’s Done (Two Resources)

staticvoid copy(String src, String dest) throws IOException {

InputStream in = new FileInputStream(src);

try {

OutputStream out = new FileOutputStream(dest);

try {

byte[] buf = newbyte[8 * 1024];

int n;

while ((n = in.read(buf)) >= 0)

out.write(buf, 0, n);

} finally {

try {

out.close();

} catch(IOException ioe) {}

}

} finally {

try {

in.close();

} catch(IOException ioe) {}

}

}

arm syntax two resources
ARM Syntax – Two Resources
  • Code is now 4 lines
    • Removed the boring nested try, catch, finally, close()clauses
  • The first exception is thrown if a problem occurs, the close() exception is hidden

staticvoid copy(String src, String dest) throws IOException {

try (InputStream in = new FileInputStream(src);

OutputStream out = new FileOutputStream(dest)) {

byte[] buf = newbyte[8192];

int n;

while ((n = in.read(buf)) >= 0)

out.write(buf, 0, n);

}

}

automatic resource management
Automatic Resource Management

ARM statement is a form of the try statement that declares one or more resources

The scope of these resource declarations is limited to the statement

When the statement completes, whether normally or abruptly, all of its resources are closed automatically

As of b89 ARM is not yet available, but definitely going to be inside JDK7

an interface must be chosen
An Interface Must be Chosen

A class must implement a designated interface to make it eligible for automatic resource management

An obvious choice would be Closeable

close() method throws IOException

What about general purpose resources?

package java.io;

importjava.io.IOException;

publicinterface Closeable {

publicvoid close() throws IOException;

}

an interface must be chosen 2
An Interface Must be Chosen (2)

It is possible to retrofit Closeable with a parameterized superinterface

Disposable would become:

package java.lang;

publicinterface Disposable<X extends Throwable> {

void close() throws X;

}

package java.io;

import java.io.IOException;

publicinterface Closeable extends Disposable<IOException> {

void close() throws IOException;

}

arm notes
ARM – Notes

No interface is chosen, nor implemented yet

As of b89

Migration

Any resource that must be closed manually should be retrofitted to implement the Disposable interface

In the JDK, this includes:

Closeable (all streams implement it)

Connection, Statement, and ResultSet

suppressed exceptions
Suppressed Exceptions

ARM discards suppressed exceptions

Proposal implies they can be saved by adding them in suppressing exception via two new methods to Throwable:

void addSuppressedException(Throwable)

Throwable[]getSuppressedExceptions()

As of b89 not implemented and it’s not clear whether they will be

what is the fuss all about
What is the Fuss All About?

Simply this:

… becomes:

<> is called the ‘diamond‘

Cannot be omitted because no difference can be made between raw HashMap and a parameterized one

[Ctrl+Shift+F]failsondiamond in NetBeans 6.9

Implemented in b89

Map<String, List<String>> anagrams =

new HashMap<String, List<String>>();

Map<String, List<String>> anagrams = new HashMap<>();

diamond advanced example
Diamond <>: Advanced Example

This is supposed to work:

…but does not yet (as of b89)

publicclass AdvancedExample {

publicstaticvoid main() {

method("", new ArrayList<>(), new ArrayList<>());

}

publicstatic <T> T method(

T a, List<T> b, List<Map<T, T>> c) {

return a;

}

}

simplified varargs method
Simplified Varargs Method…

The compiler currently generates an "unsafe operation" warning

When a programmer tries to invoke a varargs method with a non-reifiable varargs type

JDK 7 will move the warning from the call site to the method declaration

Major advantages

Reduces the total number of warnings reported to and suppressed by programmers

a picture is worth a 1000 words
A Picture is Worth a 1000 Words

/** NOT WORKING in b89, no change with jdk1.6.0_20 */

publicstaticvoid main() {

Callable<String> t = null;

//OLD: Warning: "uses unchecked or unsafe operations“

List<Callable<String>> merged = asList(t);

System.out.println(merged);

}

// NEW: Warning: "unchecked generic array creation"

privatestatic <T> List<T> asList(T... elements ) {

return Arrays.asList(elements);

}

simplified varargs example
Simplified Varargs – Example

interface Sink<T> {

void add(T... a);

}

/** NOT WORKING in b89, no change with jdk1.6.0_20 */

interface BrokenSink<T> extends Sink<T> {

// OLD: no warning

// NEW: Warning: "Overriddes non-reifiable varargs type with array"

void add(T[] a);

}

/** NOT WORKING in b89, no change with jdk1.6.0_20 */

class StringSink implements Sink<String> {

// OLD: no warning

// NEW: Warning: "override generates a more specific varargs type erasure"

publicvoid add(String... a) {}

}

collection literals
Collection Literals

Again a syntax sugar

Not yet available, so no demo 

/** NOT WORKING in b89 */

publicstaticvoid main(String... args) {

List<String> list = ["One", "Two"];

Set<String> set = {"One", "Two", "Three"};

Map<String, Integer> map = {"One": 1, "Two": 2};

// Note:

Object s = { }; // empty set;

Object m = {:}; // empty map;

}

collection indexers
Collection Indexers

Syntax sugar

/** NOT WORKING in b89 */

publicstaticvoid main(String... args) {

List<String> list =

Arrays.asList(new String[]{"a", "b", "c"});

Map<Integer, String> map =

new HashMap<Integer, String>(4);

// THE OLD WAY

String firstElement = list.get(0);

map.put(1, "One");

// THE NEW WAY (NOT IMPLEMENTED YET)

String firstElement = list[0];

map[1] = "One";

}

jsr 292 support in javac
JSR 292 Support in javac

java.dyn.InvokeDynamic will accept any method call and turn it into an invokedynamic instruction

The type java.dyn.MethodHandle will accept any argument and return types

Bytecode names acceptable to the JVM can be spelled from Java code, using #" "

java.dyn.InvokeDynamic serves as a bare reference type: anything implicitly converts to it

It can be cast to anything, but it is not a subtype of java.lang.Object

jsr 292 example
JSR 292 – Example

// Works in b89

// type (Object, int) -> boolean

boolean z =

java.dyn.InvokeDynamic.<boolean>myEquals(x, y);

// Works in b89

MethodHandle hndl = MethodHandles.lookup().findVirtual(

PrintStream.class, "println", MethodType.methodType(

void.class, String.class));

hndl.invokeGeneric(System.out, "Merhaba");

// Works in b89

String #"g 1 $!$#%" = "Text";

System.out.println(#"g 1 $!$#%");

underscores in numbers
Underscores in Numbers
  • Too much sugar can cause diabetes
  • May seem useless,butdon’tjudgetooquickly

/** WORKING in b89 */

publicstaticvoid main(String... args) {

// THE OLD WAY

int oldBillion = 1000000000;

// THE NEW WAY

int newBillion = 1_000_000_000;

out.println(oldBillion);

out.println(newBillion);

}

binary literals
Binary Literals
  • The syntax is 0b11110000;
  • See where underscores come in handy?

/** WORKING in b89 */

publicstaticvoid main(String... args) {

// THE OLD WAY

int oldBinary1 = 153;

int oldBinary2 = 128 ^ 0 ^ 0 ^ 16 ^ 8 ^ 0 ^ 0 ^ 1;

// THE NEW WAY

int newBinary = 0b1001_1001;

out.println(oldBinary1);

out.println(oldBinary2);

out.println(format("[0b1001_1001] is {0}", newBinary));

}

closures in java

Closures in Java

First-class Functions, Function Types and Lambda Expressions

what are closures
What are Closures?
  • Closures – definition
    • Closures are functions that are evaluated in an environment containing one or more bound variables [Wikipedia]
    • In English: a little snippet of code (function) that can be passed as argument of some method for subsequent execution
  • Closures come from functional programming languages like Lisp
  • Limited support for closures since JDK 1.1, in the form of anonymous classes
first class and anonymous functions
First-class and Anonymous Functions
  • First-class functionsare programming paradigm that supports
    • Data structure holding a function with its parameters and return type
    • Passing functions as arguments to other functions and invoking them
    • Returning functions as result
  • Anonymous functions
    • Functions without name (lambda functions)
    • Take some parameters and return a value
lambda expressions
Lambda Expressions
  • Lambda calculus
    • A formal mathematical system for function definition, function application and recursion
    • Typed and untyped lambda calculus
  • Lambda expressions
    • Anonymous functions that take parameters and return values, e.g.
      • x → x*x
      • (x, y) → x*x + y*y
    • A.k.a. lambda functions
project lambda
Project Lambda
  • Project Lambda
    • Goals
      • To formulate a proposal to add first-class functions, function types, and lambda expressions (informally, "closures") to Java
      • To implement a prototype suitable for inclusion in JDK 7
    • Official Web Site
      • http://openjdk.java.net/projects/lambda/
    • Status
      • Straw-man proposal, still no JSR
lambda expressions in java
Lambda Expressions in Java
  • Lambda expressions in Java use the # syntax
    • Function with no arguments, returns 42:
    • Function with int argument:
    • Function with two int arguments:

#()(42)

#(int x)(x + x)

#(int x, int y)(x * y)

lambda expressions with code block
Lambda Expressions with Code Block
  • Lambda expressions can have body
    • A Java code block:

#(int x, int y) {

int z = (int)Math.sqrt(x*x + y*y);

if (z < 10)

return x;

else if (z > 10)

return y;

else

return 0;

}

function types
Function Types
  • Function types are data types that hold a reference to lambda function or method:
  • Functions stored in variable of function type can be invoked like any other function:

#int() fortyTwo = #()(42);

#int(int) triple = #(int x)(3*x); #int(int,int) mult = #(int x, int y)(x * y);

System.out.println(fortyTwo());

int result = triple(5);

int multResult = mult(3, 5);

functions as arguments
Functions as Arguments
  • Lambda functions can be passed as arguments to a method

public long sum(int[] arr, #int(int) fn) {

long sum = 0;

for (int element : arr)

sum += fn(element);

return sum;

}

int[] arr = new int[] {1, 2, 3, 4};

long squaresSum = sum(arr, #(int x)(x*x));

System.out.println(squaresSum); // 30

functions as return value
Functions as Return Value
  • Lambda functions can be returned as result of method execution:

public #int(int) adder(int c) {

return #(int x)(x + c);

}

#int(int) a42 = adder(42);

System.out.println(a42(2)); // 44

function conversions
Function Conversions
  • Lambda functions can be converted to abstract class / interface defining a single method:

Thread th = new Thread(new Runnable() {

public void run() {

doSomeStuff();

doMoreStuff();

}

});

Thread th = new Thread(#(){

doSomeStuff(); doMoreStuff(); } )

variable capture
Variable Capture
  • We can share local state between the body of a lambda expression and its enclosing scope
    • A new keyword shared is introduced

shared int comparisonsCount = 0;

Collections.sort(data, #(String a, String b) {

comparisonsCount++;

return a.compareTo(b);

});

System.out.println(comparisonsCount);

instance capture
Instance Capture
  • The this reference of the enclosing class could be accessed in a lambda expression:

class CountingSorter {

private int comparisonsCount = 0;

Collections.sort(data,

#(String a, String b) {

comparisonsCount++;

return a.compareTo(b);

}

);

extension methods
Extension Methods
  • Extension methods allow the author of an existing interface to add methods to that interface while preserving compatibility
  • For example, we need to add a method for filtering members from any collection by given Boolean condition:

Set<Integer> set =

new Set<Integer>(new int[] {1,2,3,4,5});

Set<Integer> filteredSet =

set.filter(#boolean(int x)(x < 3));

extension methods 2
Extension Methods (2)
  • Defining extension methods:

class Collections {

static <T> Set<T> filter(

Set<T> s, #boolean(T) pred) { … }

static <S,T> Set<S> map(

Set<T> s, #S(T) func) { … }

}

interface Set<T> extends Collection<T> {

Set<T> filter(#boolean(T)) import static

Collections.filter;

<S> map(#S(T)) import static Collections.map;

}

extension methods 3
Extension Methods (3)
  • Using extension methods:

int ints = new int[] { 1, 2, 3, 4, 5 };

int[] transformedInts =

s.filter(#(int x)(x % 2 == 0))

.map(#(int x)(x + 3));

// transformedInts = { 5, 7 }

int[] transformedInts =

Collections.map(

Collections.filter(s, #(int x)(x % 2 == 0)),

#(int x)(x + 3)

);

parallel arrays api
Parallel Arrays API
  • ParallelArray<T> is ideal candidate for extension methods
    • Can utilize efficiently multi-core / multiprocessor systems
  • The class ParallelArray<T> allows parallel aggregate operations over a collection
    • Apply transformation to each element
    • Map each element to a new element
    • Select subset of the elements by predicate
    • Reduce elements to a single value (e.g. sum)
nio2 introduction
NIO2 – Introduction

New I/O or non-blocking I/O, usually called NIO

Collection of Java APIs that offer features for intensive I/O operations

It was introduced with the J2SE 1.4

NIO was developed under the Java Community Process as JSR 51

As of 2006, an extension to NIO, called NIO2, is being developed under JSR 203

JSR 203 is scheduled to be included in JDK 7

cool new things resolve
Cool New Things: resolve()

resolve() – resolves a relative path

publicstaticvoid resolve() {

FileSystem fileSystem = FileSystems.getDefault();

Path currentDir = fileSystem.getPath(".");

Path srcDir = fileSystem.getPath("src");

Path file1 = fileSystem.getPath("./Test.java");

Path file2 = fileSystem.getPath(“../Copy.java");

System.out.println("file2: " + currentDir.resolve(srcDir).resolve(file2));

}

cool new things relativize
Cool New Things: relativize()

relativize() – makes path relative

publicstaticvoid relativize() {

FileSystem fileSystem = FileSystems.getDefault();

Path source = fileSystem.getPath(".");

Path temp = fileSystem.getPath("/temp");

Path relativeSource =

source.toAbsolutePath(). relativize(temp.toAbsolutePath());

System.out.println(relativeSource);

}

how to copy a file
How to Copy a File

Up to Java 6 (w/o channels) it looks like this:

Familiar?

Most developers write this incorrectly

try {

from = new FileInputStream(fromFile);

to = new FileOutputStream(toFile);

byte[] buffer = newbyte[4096];

int bytesRead;

while ((bytesRead = from.read(buffer)) != -1)

to.write(buffer, 0, bytesRead); // write

} finally {

// Close the streams "to" and "from"

}

how to copy a file 2
How to Copy a File (2)

java.io.File is used to represent a file

@since 1.0

Is there a way to copy metadata?

JDK7: java.io.File -> java.nio.file.Path

java.io.File won’t be deprecated, but should

Path is a better name (might be a dir, right?)

FileSystem local = FileSystems.getDefault();

Path from = local.getPath(FileName);

Path to = local.getPath(toFileName);

from.copyTo(to);

// java.io.File -> java.nio.filePath

Path p = new File("/foo/bar.txt").toPath();

the problem
The Problem

Bug ID: 4670071

Submit Date: 17-APR-2002

Release Fixed: 7 (b47)

Means: Fixed in JDK7 (build 47)

b47 got released Q1 2009

The bug is about a classloader deadlock

deadlocks as caused by non-interceptibleloadClassInternal() calls

How many of you know about the existence of bug 4670071?

what is an oop
What is an oop?

An "oop", or "ordinary object pointer" in the JVM is a managed object pointer

It is normally the same size as a native machine pointer

64 bits on an 64-bit OS

32 bits on an 32-bit OS

32-bit JVM can address less than 4GB

64-bit JVM can address all the available RAM

But this costs a lot of memory lost in oops

compressed oops
Compressed oops
  • Compressed oops allow to address up to 32 GB RAM with 32-bit pointers
    • The address space is mapped using a 64-bit base and 32-bit oop
    • This allows applications to address up to four billion objects (not bytes)
    • Java heap can grow up to 32 GB
garbage first gc g11
Garbage-First GC (G1)

G1 (garbage-first) garbage collector

Improved performance and less freeze time

Server-style garbage collector

Targeted for multi-processors with large memories

Meets a soft real-time goal with high probability

Added in Milestone1 (02.01.2009)

Released in Java 6 update 6u14

urlclassloader close
URLClassLoader.close()

URLClassLoader has new method called close()

since b48 of JDK 7

Closes any JAR files that were open by the loader

Allows the application to delete/replace these files and if necessary to create new loaders

Invalidates the loader, so that no new classes can be loaded from it

/** @since 1.7 */ urlClassLoader.close();

unicode 5 1 in java 7
Unicode 5.1 in Java 7

Java 6 is Unicode 4.0 compliant

Java 7 will be Unicode 5.1 compliant

Most up-to-date version of Unicode is 5.2 (October 2009)

What\'s new in Unicode 5 ?

Unicode 5.0 will include 1,369 new characters and 9 new blocks (~alphabets)

Unicode 5.1 will have 1,624 additional char’s making a grand total of 100,713 breaking the 100K mark for the first time

slide99
SCTP

Stream Control Transmission Protocol (SCTP) is a Transport Layer protocol

serving in a similar role as TCP and UDP

Features of SCTP include:

Multihoming support: both endpoints of a connection can consist of more than one IP

Chunks delivered within independent streams

Protect against flooding attacks

No Windows supports SCTP

jdk7 the sctp project
JDK7: The SCTP Project

The goal of this Project is:

To develop an API for the Stream Control Transport Protocol (SCTP)

And a corresponding OpenJDK prototype

The API is implementation agnostic

Included in build 56

Could be hacked to work with JDK6

Currently only Solaris is supported

slide102
SDP

The Sockets Direct Protocol (SDP) is a networking protocol originally defined by the InfiniBand Trade Association

Transport agnostic protocol for Remote Direct Memory Access (RDMA)

RDMA is a direct memory access from one computer’s memory into another’s without involving either one\'s operating system

JDK7’s SDP implementation works, unfortunately, only on Solaris

resources java chronology
Resources – Java Chronology
  • JDK 7 – Features
    • http://openjdk.java.net/projects/jdk7/features/
  • JDK 7 – Milestones
    • http://openjdk.java.net/projects/jdk7/milestones/
resources dynamic langs
Resources – Dynamic Langs
  • New JDK 7 Feature: Support for Dynamically Typed Languages in the Java Virtual Machine
    • http://java.sun.com/developer/technicalArticles/DynTypeLang/
  • John Rose\'s weblog at Sun Microsystems
    • http://blogs.sun.com/jrose/
  • JSR 292: Supporting Dynamically Typed Languages on the Java Platform
    • http://jcp.org/en/jsr/detail?id=292
resources project jigsaw
Resources – Project Jigsaw

Project Jigsaw: Language changes for Modules

http://openjdk.java.net/projects/jigsaw/doc/language.html

Project Jigsaw – Mark Reinhold’s Blog

http://blogs.sun.com/mr/entry/jigsaw

Is the JDK Losing its Edge(s)?

http://blogs.sun.com/alanb/entry/is_the_jdk_losing_its

resources jsr 308
Resources – JSR 308

Type Annotations Specification (JSR 308)

http://types.cs.washington.edu/jsr308/specification/java-annotation-design.html

Type Annotations FAQ (JSR 308)

http://types.cs.washington.edu/jsr308/jsr308-faq.html

The Checker Framework: Custom Pluggable Types for Java

http://types.cs.washington.edu/checker-framework/current/checkers-manual.html

resources project coin
Resources – Project Coin

Project Coin

http://wikis.sun.com/display/ProjectCoin/2009ProposalsTOC

http://mail.openjdk.java.net/pipermail/coin-dev/2009-February/000001.html

Strings in switch

http://mail.openjdk.java.net/pipermail/coin-dev/2009-February/000001.html

Automatic Resource Management

http://mail.openjdk.java.net/pipermail/coin-dev/2009-February/000011.html

resources project coin 2
Resources – Project Coin (2)
  • Improved Type Inference for Generic Instance Creation
      • http://mail.openjdk.java.net/pipermail/coin-dev/2009-February/000009.html
  • Simplified Varargs Method Invocation
      • http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000316.html
  • Collection Literals
      • http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001193.html
resources project coin 3
Resources – Project Coin (3)
  • Indexing access syntax for Lists and Maps
      • http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001108.html
  • Language support for JSR 292
      • http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001077.html
  • Binary Literals
      • http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001627.html
  • Underscores in numbers
    • http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001208.html
resources closures
Resources – Closures
  • Project Lambda
    • http://openjdk.java.net/projects/lambda/
  • Project Lambda: Straw-Man Proposal
    • http://cr.openjdk.java.net/~mr/lambda/straw-man/
  • Closures for Java – Mark Reinhold’s Blog
    • http://blogs.sun.com/mr/entry/closures
resources nio2
Resources – NIO2

Java New I/O

http://en.wikipedia.org/wiki/New_I/O

JSR 203: The Open Road – java.nio.file

http://today.java.net/pub/a/today/2008/07/03/jsr-203-new-file-apis.html

resources compressed oops
Resources – Compressed oops

Compressed oops in the Hotspot JVM

http://wikis.sun.com/display/HotSpotInternals/CompressedOops

Wikipedia – 64-bit

http://en.wikipedia.org/wiki/64-bit

ILP32, LP64, and LLP64

http://wiki.wireshark.org/Development/Win64

C Programming Language

http://en.wikipedia.org/wiki/C_(programming_language)

resources garbage collection
Resources – Garbage Collection

Garbage-First Garbage Collection

http://research.sun.com/jtech/pubs/04-g1-paper-ismm.pdf

JavaOne: G1 Garbage Collector

http://tech.puredanger.com/2008/05/09/javaone-g1-garbage-collector

Garbage Collection – Wikipedia

http://en.wikipedia.org/wiki/Garbage_collection_(computer_science)

Wikipedia – Hard and Soft Real-time Systems

http://en.wikipedia.org/wiki/Real-time_computing#Hard_and_soft_real-time_systems

resources upgrade classloader architecture
Resources – Upgrade ClassLoader Architecture

Draft Proposal for ClassLoader Deadlock Fix

http://www.mail-archive.com/[email protected]/msg00863.html

java.lang.ClassLoader.loadClassInternal(String) is Too Restrictive

http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4670071

resources url classloader
Resources – URL ClassLoader

Closing a URLClassLoader

http://blogs.sun.com/michaelmcm/entry/closing_a_urlclassloader

Class URLClassLoader – close()

http://download.java.net/jdk7/docs/api/java/net/URLClassLoader.html#close()

resources unicode 5 1
Resources – Unicode 5.1

JDK 7 – Features – Unicode 5.1

http://openjdk.java.net/projects/jdk7/features/#f497

What\'s new in Unicode 5.0?

http://babelstone.blogspot.com/2005/11/whats-new-in-unicode-50.html

What\'s new in Unicode 5.1?

http://babelstone.blogspot.com/2007/06/whats-new-in-unicode-51.html

resources sctp
Resources – SCTP

SCTP Project

http://openjdk.java.net/projects/sctp/

resources sdp
Resources – SDP

Understanding the Sockets Direct Protocol

http://java.sun.com/docs/books/tutorial/sdp/sockets/index.html

Sockets Direct Protocol – Wikipedia

http://en.wikipedia.org/wiki/Sockets_Direct_Protocol

Remote Direct Memory Access

http://en.wikipedia.org/wiki/Remote_Direct_Memory_Access

Zero-copy

http://en.wikipedia.org/wiki/Zero-copy

resources authors
Resources – Authors
  • Authors of this presentation:
    • Svetlin Nakov
      • http://www.nakov.com/blog/
    • Mihail Stoynov
      • http://mihail.stoynov.com/blog/
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