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The Future of the Java Platform:Java SE 7 & Java SE 8

Terrence BarrSenior Technologist, Mobile & Embedded Technologies

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The preceding is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions.

The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle.

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Project Coin (JSR 334)Small Language Changes

The DaVinci MachineMultiple Languages on the JVMinvokedynamic (JSR 292)

Agenda

Library changesMiscellaneous Updates

JSR 337: Java SE 8 Release Contents

SmallSmall(Language)(Language)

ChangesChangesProject CoinProject Coin

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Evolving the LanguageFrom “Evolving the Java Language” - JavaOne 2005

• Java language principles– Reading is more important than writing

– The language should not hide what is happening

– Code should do what it seems to do

– Simplicity matters

– Every “good” feature adds more “bad” weight

– Sometimes it is best to leave things out

• One language: with the same meaning everywhere• No dialects

• We will evolve the Java language• But cautiously, with a long term view

• “first, do no harm”

• Beware: Changes have many downstream implications (spec, tests, implementation(s), tools, compatibility, future, ...)

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Java Standard Edition (Java SE) vs.Java Development Kit (JDK)

• Java SE• Definition of the software

platform• Specification documents• Implementation• Test suite (TCK)

• Implemented by several groups

• Produced in the JCP

• Java Development Kit• Oracle's implementation of

Java SE• Additional features not in

the spec• Tools and documentation• Deployment and

management capabilities• Performance features• Produced in the OpenJDK

project

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Java SE 7

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Section DividerSmallSmall

(Language)(Language)ChangesChanges

Project CoinProject Coin

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Project Coin Constraints

• Small language changes• Small in specification, implementation, testing• No new keywords!• Wary of type system changes

• Coordinate with larger language changes– Project Lambda– Modularity

• One language, one javac

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Better Integer Literal

• Binary literals

• With underscores for clarity

int mask = 0b101010101010;

int mask = 0b1010_1010_1010;long big = 9_223_783_036_967_937L;

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String Switch Statement

• Today case label includes integer constants and enum constants

• Strings are constants too (immutable)

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Discriminating Strings Today

int monthNameToDays(String s, int year) {

if("April".equals(s) || "June".equals(s) ||"September".equals(s) ||"November".equals(s))

return 30;

if("January".equals(s) || "March".equals(s) ||"May".equals(s) || "July".equals(s) ||"August".equals(s) || "December".equals(s))

return 31;

if("February".equals(s))...

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Strings in Switchint monthNameToDays(String s, int year) {

switch(s) {case "April": case "June":case "September": case "November":

return 30;

case "January": case "March":case "May": case "July":case "August": case "December":

return 31;

case "February":...

default:...

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Simplifying Generics

• Pre-genericsList strList = new ArrayList();

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Simplifying Generics

• Pre-genericsList strList = new ArrayList();

• With GenericsList<String> strList = new ArrayList<String>();

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Simplifying Generics

• Pre-genericsList strList = new ArrayList();

• With GenericsList<String> strList = new ArrayList<String>();List<Map<String, List<String>> strList =

new ArrayList<Map<String, List<String>>();

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Diamond Operator

• Pre-genericsList strList = new ArrayList();

• With Generics

• With diamond (<>) compiler infers type

List<String> strList = new ArrayList<String>();List<Map<String, List<String>> strList =

new ArrayList<Map<String, List<String>>();

List<String> strList = new ArrayList<>();List<Map<String, List<String>> strList =

new ArrayList<>();

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Simplifying Resource Use

InputStream in = new FileInputStream(src);OutputStream out = new FileOutputStream(dest);

byte[] buf = new byte[8192];int n;

while (n = in.read(buf)) >= 0) out.write(buf, 0, n);

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Simplifying Resource Use

InputStream in = new FileInputStream(src);OutputStream out = new FileOutputStream(dest);

try { byte[] buf = new byte[8192]; int n; while (n = in.read(buf)) >= 0) out.write(buf, 0, n);} finally { in.close(); out.close();}

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Simplifying Resource Use

InputStream in = new FileInputStream(src);try { OutputStream out = new FileOutputStream(dest); try { byte[] buf = new byte[8192]; int n; while (n = in.read(buf)) >= 0) out.write(buf, 0, n); } finally { out.close(); }} finally { in.close();}

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Automatic Resource Management

try (InputStream in = new FileInputStream(src), OutputStream out = new FileOutputStream(dest)){ byte[] buf = new byte[8192]; int n; while (n = in.read(buf)) >= 0) out.write(buf, 0, n);}

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Exceptions Galoretry {

...} catch(ClassNotFoundException cnfe) {

doSomething(cnfe);throw cnfe;

} catch(InstantiationException ie) {log(ie);throw ie;

} catch(NoSuchMethodException nsme) {log(nsme);throw nsme;

} catch(InvocationTargetException ite) {log(ite);throw ite;

}

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Multi-Catch

try {// Reflective operations calling Class.forName,// Class.newInstance, Class.getMethod,// Method.invoke, etc.

} catch (final ClassCastException e) { doSomething(e); throw e;} catch(final InstantiationException |

NoSuchMethodException |InvocationTargetException e) {

log(e);throw e;

}

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More Precise Rethrowtry {

// Reflective operations calling Class.forName,// Class.newInstance, Class.getMethod,// Method.invoke, etc.

} catch(final ReflectiveOperationException e) {//e means any of the subtype thrown from try {}log(e);throw e;

}

ReflectiveOperationException

ClassNotFoundException

InstantiationException

NoSuchMethodException

InvocationTargetException

http://download.java.net/jdk7/docs/api/java/lang/ReflectiveOperationException.html

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The DaVinci Machine ProjectJSR 292A multi-language renaissance for the JVMopenjdk.java.net/projects/mlvm

● Dynamic Invocation● InvokeDynamic bytecode

● Method Handles

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JVM Architecture

• Stack based • Push operand on to the stack• Instructions operates by popping data off the stack• Pushes result back on the stack

• Data types • Eight primitive types, objects and arrays

• Object model – single inheritance with interfaces• Method resolution

• Receiver and method name• Statically typed for parameters and return types• Dynamic linking + static type checking

• Verified at runtime

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JVM Specification

“The Java virtual machine knows nothing about the Java

programming language, only of a particular binary format, the class

file format.”

1.2 The Java Virtual Machine Spec.

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Languages Running on the JVM

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Clojure

Tcl

JavaScript

v-language

CAL

Sather

Funnel

MiniPLAN

Lisp

Scheme

Basic

Logo JHCR

TermWare

Drools

Prolog

LLP

JESS

Eiffel

Smalltalk

C#

G

Groovy

Nice

Anvil

Hojo

Correlate

Ada

Bex Script

Tea

PHP

PhobosSleep

FScript

JudoScript

JRuby

ObjectScript

Jickle

Yoix

Simkin

BeanShell

DawnWebL

iScript

Jython

Pnuts

Yassl

Forth

PiccolaSALSA

Processing

Zigzag

Tiger

Tiger

IconPascal

Oberon

Modula-2

Luck

E

Rexx Scala

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Method Calls● Calling a method is cheap (VMs can even inline!)● Selecting the right target method can be expensive

● Static languages do most of their method selection at compile time

● Single-dispatch on receiver type is left for runtime

● Dynamic languages do almost none at compile time● But it would be nice to not have to re-do method selection

for every single invocation

● Each Language has its own ideas about linkage

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InvokeDynamic Bytecode

• JVM currently has four ways to invoke method• Invokevirtual, invokeinterface, invokestatic, invokespecial

• All require full method signature data

• InvokeDynamic will use method handle• Effectively an indirect pointer to the method

• When dynamic method is first called bootstrap code determines method and creates handle

• Subsequent calls simply reference defined handle• Type changes force a re-compute of the method

location and an update to the handle• Method call changes are invisible to calling code

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LibraryChanges

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New I/O 2 (NIO2) Libraries

• Original Java I/O APIs presented challenges for developers • Not designed to be extensible• Many methods do not throw exceptions as expected

• rename() method works inconsistently

• Developers want greater access to file metadata

• Java NIO2 solves these problems

JSR 203

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Java NIO2 Features

• Path is a replacement for File• Biggest impact on developers

• Better directory support• list() method can stream via iterator

• Entries can be filtered using regular expressions in API

• Symbolic link support• Two security models (POSIX, ACL based on NFSv4)• java.nio.file.Filesystem

• interface to a filesystem (FAT, ZFS, Zip archive, network, etc)

• java.nio.file.attribute package• Access to file metadata

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Concurrency APIs

• JSR166y• Update to JSR166x which was an update to JSR166

• Adds a lightweight task framework• Also referred to as Fork/Join

• Uses ParallelArray• Greatly simplifies use of many cores/processors for tasks that

can easily be separated

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Client Libraries

• Nimbus Look and Feel• Platform APIs for shaped and translucent windows• JLayer (formerly from Swing labs)• Optimized 2D rendering

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Nimbus Look and Feel

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JLayer componentEasy enrichment for Swing components

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JLayer componentThe universal decorator

• Transparent decorator for a Swing component• Controls the painting of its subcomponents• Catches all input and focus events for the whole hierarchy

// wrap your component with JLayerJLayer<JPanel> layer = new JLayer<JPanel>(panel);

// custom ui provides all extra functionalitylayer.setUI(myLayerUI);

// add the layer as usual componentframe.add(layer);

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Miscellaneous Updates

• Security• Eliptic curve cryptography• TLS 1.2

• JAXP 1.4.4 (Java API for XML processing)• JAX-WS 2.2 (Java API for XML Web Services)• JAXB 2.2 (Java Architecture for XML Binding)• ClassLoader architecture changes

• close() for URLClassLoader

• Javadoc support for CSS

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Platform Support

• Windows (x86)• Linux (x86)

• Redhat• Ubuntu

• Solaris (x86)• New: Apple OSX (x86)

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Java SE 8

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More Project CoinSmall Language Changes

Project Lambda (JSR 335)Closures and moreBetter support for multi-core processors

Project JigsawModularising the Java Platform

Java SE 8

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The Modular Java Platform

• Enables escape from “JAR Hell”– Eliminates class path– Package modules for automatic download & install– Generate native packages – deb, rpm, ips, etc

• Enables significant performance improvements– Incremental download → fast classloading– Optimise module content during installation

• Platform scalability – down to small devices– Well-specified SE subsets can fit into small devices

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module-info.java

module com.foo @ 1.0.0 {class com.foo.app.Mainrequires org.bar.lib @ 2.1-alpha;requires edu.baz.util @ 5.2_11;provides com.foo.app.lib @ 1.0.0;

}

Module name

VersionEntry point

Dependency

Virtual module

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Project LambdaClosures and moreopenjdk.java.net/projects/lambda

● Lambda expressions● SAM conversion with target typing● Method references● Library enhancements for internal iteration● Default methods for interface evolution

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Hypothetical Internal Iteration

• Not inherently serial– students traversal not determined by developer– Looks like a functional language

• Anonymous inner class!

double highestScore = students.filter(new Predicate<Student>() {

public boolean isTrue(Student s) {return s.gradYear == 2010;

}}).map(new Extractor<Student,Double>() {

public Double extract(Student s) {return s.score;

}}).max();

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Introducing Lambda Expressions

• Lambda expressions introduced with #– Signal to the JVM to defer execution of the code– Body may be an expression

• Lambda expression are not syntactic sugar for anonymous inner class – Implemented with MethodHandle from JSR-292

double highestScore = students.filter(#{ Student s -> s.gradYear == 2010 }).map(#{ Student s -> s.score }).max();

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Roadmaps Are Approved!

• JSRs approved by JCP– JSR 334: Small enhancements to the Java language– JSR 335: Lambda expressions for the Java language– JSR 336: Java SE 7 Release Contents– JSR 337: Java SE 8 Release Contents

• OpenJDK Releases in 2011 & 2012– Committed Features List for 2011:

• openjdk.java.net/projects/jdk7/features

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Conclusions

• Java SE 7• Incremental changes• Evolutionary, not revolutionary• Good solid set of features to make developers life easier

• Java SE 8• Major new features: Modularisation and Closures• More smaller features to be defined

• Java Evolution Continues • Grow and adapt to the changing world of IT• Oracle and its partners are committed to a vibrant and

evolving Java ecosystem

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