Michal Malohlava Java 7 : Quo vadis? DISTRIBUTED SYSTEMS RESEARCH GROUP http://dsrg.mff.cuni.cz/ CHARLES UNIVERSITY IN PRAGUE Faculty of Mathematics and Physics

Michal Malohlava

Java development process Language extension Related projects Java Module System Conclusion Outline

Java development process

Language extension

Related projects

Java Module System

Conclusion

JDK Official Sun's Java Source code released (GPL v.2) 18months release interval JDK6 fall 2006 => JDK7 spring 2008 (January 2009:) Still no official JSR ( Java Specification Request ) only many proposals of Java7 features/anti-features OpenJDK Free implementation of JDK by Java community OpenJDK 6 will be based on OpenJDK 7 Now only Modules project - JSR 277, JSR 294 Java development process

JDK

Official Sun's Java

Source code released (GPL v.2)

18months release interval

JDK6 fall 2006 => JDK7 spring 2008 (January 2009:)

Still no official JSR ( Java Specification Request )

only many proposals of Java7 features/anti-features

OpenJDK

Free implementation of JDK by Java community

OpenJDK 6 will be based on OpenJDK 7

Now only Modules project - JSR 277, JSR 294

No official JSR Still in discussion JUG (Java User Group) Unofficial JSR for JDK7 Published on 7 th November Specify Closures Generics, enum, switch enhancements Chained invocations, extension methods Exception catching Language extensions

No official JSR

Still in discussion

JUG (Java User Group)

Unofficial JSR for JDK7

Published on 7 th November

Specify

Closures

Generics, enum, switch enhancements

Chained invocations, extension methods

Exception catching

Generics Constructors without duplicate declaration Map<String, List<String>> anagrams = new HashMap<>(); instead of Map<String, List<String>> anagrams = new HashMap<String, List<String>>(); Generics are not still covariant! List<Integer> li = new ArrayList<Integer>(); List<Number> ln = li; // illegal ln.add(new Float(3.1415)); // legal More type safe packages JDK 5: static Object newInstance(Class<?> componentType, int size) Because of backward compatibility JDK 5,7: static<T> T[] newInstance(Class<T> componentType, int size) More type-safe, can be called Array.<String>newInstance(String.class, 10) Inference of method arguments static<E> Set<E> emptySet(); void print(Set<Man> men) {...} Call: print(Collection.emptySet()) // in JDK5,6 is necessary to explicitly specify which method should be called: Collection.<Man>emptySet(); Template type information available at runtime Lang. Ext. - JUG proposal

Generics

Constructors without duplicate declaration

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

Generics are not still covariant!

List<Integer> li = new ArrayList<Integer>(); List<Number> ln = li; // illegal ln.add(new Float(3.1415)); // legal

More type safe packages

JDK 5: static Object newInstance(Class<?> componentType, int size)

Because of backward compatibility

JDK 5,7: static<T> T[] newInstance(Class<T> componentType, int size)

More type-safe, can be called Array.<String>newInstance(String.class, 10)

Inference of method arguments

static<E> Set<E> emptySet();

void print(Set<Man> men) {...}

Call: print(Collection.emptySet()) // in JDK5,6 is necessary to explicitly specify which method should be called: Collection.<Man>emptySet();

Template type information available at runtime

Enum JDK6: Enum implements Comparable, but cannot be used in expressions with <, >, >=, <= JDK7: Strings in switch Use strings as constants in switch-statement instead of bundle of equals: Lang. Ext. - JUG proposal enum Size {SMALL, MEDIUM, LARGE}; if (mySize < yourSize) { /* ... */ } switch (s) { “ yellow” : /* ... */ break ; “ red” : /* ... */ break ; defaul t: /* ... */ break ; } JDK7 JDK7

Enum

JDK6: Enum implements Comparable, but cannot be used in expressions with <, >, >=, <=

JDK7:

Strings in switch

Use strings as constants in switch-statement instead of bundle of equals:

Chained invocations Reuse the receiver of previous call in case of a call of a method returning void Method extensions A way how to extend existing interface by utility methods Static imported method can be used as a member of its first argument Lang. Ext. - JUG proposal public class Beana { public void setName(String void) {} public void setDate(Date date) {} } Beana a = new Beana() .setName(“name”) .setDate(new Date()); import static java.util.Collections.sort; ... List<String> list = ...; list.sort(); JDK7

Chained invocations

Reuse the receiver of previous call in case of a call of a method returning void

Method extensions

A way how to extend existing interface by utility methods

Static imported method can be used as a member of its first argument

Catching multiple exception types To avoid repeating code Lang. Ext. - JUG proposal More flexible checking of re-thrown exception When we need to catch all exceptions, do something with them and re throw them Re-thrown exception is threated as if it can throw only checked exceptions occurring in the try block public void test() throws IOException { try { doSomething(); } catch ( final Throwable ex) { throw ex; } } try { return clazz.newInstance(); } catch (InstantiationException | IllegalAccessException e) { /* .. */ } public void doSomething throws IOException {} public void test() throws Throwable { try { doSomething(); } catch (Throwable ex) } throw ex; } JDK7 JDK7 JDK5

Catching multiple exception types

To avoid repeating code

More flexible checking of re-thrown exception

When we need to catch all exceptions, do something with them and re throw them

Re-thrown exception is threated as if it can throw only checked exceptions occurring in the try block

Creation of XML fragments XML embedded in Java code <tag> or #tag Data coders in according to XSD date/time XPath language support Lang. Ext. - XML lang. support public void addMember(XML xml, String name, Integer age) { xml.addChild(<member> <name> { name } </name> <age> { 26 } </age> </member>); } public void makeYounger(XML fs, Integer newAge) { List<XML> l = fs.findAll(“member[age>25]”); for (XML a : l) { a.get(“age”).set(newAge); } } JDK7 JDK7

Creation of XML fragments

XML embedded in Java code

<tag> or #tag

Data coders in according to XSD

date/time

XPath language support

Closures Similar to delegates in C# Anonymous functions Function type Local functions Main idea: translate closure to interface (similar to creating anonymous classes) Lang. Ext. - closures {String, String => String} simpleConcat = {String a, String b => a+b }; String s = “DS”; String g = “RG”; String dsrg = simpleConcat.invoke(s,t); interface Func<R extends String, A1 super String, A2 super String> { public R invoke(A1, A2); } ↔ Locks.withLock(lock, {=> doSomething()}); Collections.map(strings, {Strings s => Integer.decode(s)}); JDK7

Closures

Similar to delegates in C#

Anonymous functions

Function type

Local functions

Main idea: translate closure to interface (similar to creating anonymous classes)

Additional information @Licence Annotations for static analysis of code @NonNull @NonEmpty @ReadOnly @Existing @Critical Lang. Ext. - annotation extension

Additional information

@Licence

Annotations for static analysis of code

@NonNull

@NonEmpty

@ReadOnly

@Existing

@Critical

Operator overloading (BigDecimal) Arithmetic operators for BigDecimal Lightweight reflection 64bit index for arrays XQuery support (JSR 225) Resource Consumption Management API (JSR 284) Performance policies (CPU, heap consumption per application/thread, reservations) Null-safe types public void method(#K key) # marks not-null parameter Checked at compile time (globally, per-method,...) (#) casting operator Alternative to @NonNull annotation Lang. Ext. - proposed enhancements

Operator overloading (BigDecimal)

Arithmetic operators for BigDecimal

Lightweight reflection

64bit index for arrays

XQuery support (JSR 225)

Resource Consumption Management API (JSR 284)

Performance policies (CPU, heap consumption per application/thread, reservations)

Null-safe types

public void method(#K key)

# marks not-null parameter

Checked at compile time (globally, per-method,...)

(#) casting operator

Alternative to @NonNull annotation

Separated projects Almost work in the current version of Java Proposed to be part of JDK7 Java Modules Beans bindings, validation Swing application API ... Related projects

Separated projects

Almost work in the current version of Java

Proposed to be part of JDK7

Java Modules

Beans bindings, validation

Swing application API

...

Superpackages (JSR 294) Why? To hide unnecessary packages. Superpackage is a named collection of packages or superpackages, classes Accessibility defined by superpackages Compiled, loaded and checked by JVM at runtime Define development module for JSR 277 (Java Module System) Separate compilation ? Not yet specified Rel. projects – modules superpackage jdk { member package java.util; member package java.io; member package sun.io; // Impl detail export java.util.*; // Public API export java.io.*; } JDK7

Superpackages (JSR 294)

Why? To hide unnecessary packages.

Superpackage is a named collection of packages or superpackages, classes

Accessibility defined by superpackages

Compiled, loaded and checked by JVM at runtime

Define development module for JSR 277 (Java Module System)

Separate compilation ?

Not yet specified

Java Modules (JSR 277) Specifies: Modules, Versioning, Repository, Runtime support Development module (=superpackage) => deployment module (JAM – Java Module) Meta-info (generated from devel. module) Compiled code Resources Versioning Simple major/minor versions Intervals, expressions e.g 1.3* = <1.3, 1.4) Rel. projects – modules

Java Modules (JSR 277)

Specifies:

Modules, Versioning, Repository, Runtime support

Development module (=superpackage) => deployment module (JAM – Java Module)

Meta-info (generated from devel. module)

Compiled code

Resources

Versioning

Simple major/minor versions

Intervals, expressions e.g 1.3* = <1.3, 1.4)

Rel. projects – modules Repository Can store more than one version of module Bootstrap repository Contains core modules (Java SE) Always presented in system Application repository Modules specific for application Delegation model of repositories Parent repository Search is delegated to the parent repository Insulating of modules Other features Repository reload, sharing modules among repositories (repository interchange format) Changed classloading

Repository

Can store more than one version of module

Bootstrap repository

Contains core modules (Java SE)

Always presented in system

Application repository

Modules specific for application

Delegation model of repositories

Parent repository

Search is delegated to the parent repository

Insulating of modules

Other features

Repository reload, sharing modules among repositories (repository interchange format)

Changed classloading

OSGi and JAM Comparison – special seminar Rel. projects – modules and OSGi

OSGi and JAM

Comparison – special seminar

JSR 296 Framework for Swing applications library for typical operations: ApplicationContext Provides resource, task management, session storage. Each application has one ApplicationContext Application lifecycle Rel. projects – SWING API

JSR 296

Framework for Swing applications

library for typical operations:

ApplicationContext

Provides resource, task management, session storage.

Each application has one ApplicationContext

Application

lifecycle

Beans bindings (JSR 295) Keep properties of beans synced (bindings), listeners to properties... the project works with JDK5 Mainly focused on SWING Property keyword Spec. is really vague: No more getter/setters In fact generates inner class with property getter/setters Property per-type Access attribute member#surname = “Sac” Access property object member##surname ?Readonly properties? Rel. projects – beans class Person { private String surname; private Integer age; private Person mother; } // Bean property Property surnameP = BeanProperty.create(“surname”); // EL properties – JSP syntax Property motherSurnameP = BeanProperty.create(“${mother.surname}”); Property isTeenP = BeanProperty.create(“${age < 20}”); // m stores information about a person System.out.println(“Member surname = “ + surnameP.getValue(m)); System.out.println(“Member's mother surname = “ + surnameP.getValue(M)); Binding b = Bindings.createAutoBinding(READ_WRITE, m, surnameP,m , motherSurnameP); b.bind(); // the call affects attribute m.surname motherSurnameP.setValue(m, “NewSurname”);

Beans bindings (JSR 295)

Keep properties of beans synced (bindings), listeners to properties...

the project works with JDK5

Mainly focused on SWING

Property keyword

Spec. is really vague:

No more getter/setters

In fact generates inner class with property getter/setters

Property per-type

Access attribute member#surname = “Sac”

Access property object member##surname

?Readonly properties?

Beans Validation (JSR 303) Bindings validation ( à la Hibernate Validator) constraints via annotations, e.g.: @NotNull, @NotEmpty @Min(value=), @Max(value=) @Length(min=, max=), @Range(min=,max=) @Past/@Future, @Email ... New constraint = new annotation + new class Rel. projects – beans

Beans Validation (JSR 303)

Bindings validation ( à la Hibernate Validator)

constraints via annotations, e.g.:

@NotNull, @NotEmpty

@Min(value=), @Max(value=)

@Length(min=, max=), @Range(min=,max=)

@Past/@Future, @Email

...

New constraint = new annotation + new class

Improvements of JSR 166 (Concurrency utilities) Fork-join concept Fine-grained parallel computation framework Divide problems to subproblems, solve it, join the results Subproblems are executed in parallel, current thread waits until they complete coInvoke(task1, task2) Work-stealing Each thread has deque of tasks, instead of sleeping try to steal and execute a task from other busy threads TransferQueue (type of BlockingQueue ) Producer side blocking until the consumers is ready Rel. projects – concurrent framework

Improvements of JSR 166 (Concurrency utilities)

Fork-join concept

Fine-grained parallel computation framework

Divide problems to subproblems, solve it, join the results

Subproblems are executed in parallel, current thread waits until they complete

coInvoke(task1, task2)

Work-stealing

Each thread has deque of tasks, instead of sleeping try to steal and execute a task from other busy threads

TransferQueue (type of BlockingQueue )

Producer side blocking until the consumers is ready

Improvements of JSR 166 (Concurrency utilities) Fork-join concept Fine-grained parallel computation framework Divide problems to subproblems, solve it, join the results Subproblems are executed in parallel, current thread waits until they complete coInvoke(task1, task2) Work-stealing Each thread has deque of tasks, instead of sleeping try to steal and execute a task from other threads TransferQueue (type of BlockingQueue ) Producer side blocking until the consumers is ready Rel. projects – concurrent framework // PSEUDOCODE Result solve(Problem problem) { if (problem.size < SEQUENTIAL_THRESHOLD) return solveSequentially(problem); else { Result left, right; INVOKE-IN-PARALLEL { left = solve(extractLeftHalf(problem)); right = solve(extractRightHalf(problem)); } return combine(left, right); } } JDK7

Improvements of JSR 166 (Concurrency utilities)

Fork-join concept

Fine-grained parallel computation framework

Divide problems to subproblems, solve it, join the results

Subproblems are executed in parallel, current thread waits until they complete

coInvoke(task1, task2)

Work-stealing

Each thread has deque of tasks, instead of sleeping try to steal and execute a task from other threads

TransferQueue (type of BlockingQueue )

Producer side blocking until the consumers is ready

JVM change Invokedynamic (JSR 292) Improvement of scripting engine (JSR 223) New byte code instruction (type free invokevirtual) Support for dynamically typed languages (Jython, Groovy) Jython – code written in Python, compiled into byte code at runtime, run in JVM Target of call/parameters need not to be statically known Rel. projects – invokedynamic

JVM change

Invokedynamic (JSR 292)

Improvement of scripting engine (JSR 223)

New byte code instruction (type free invokevirtual)

Support for dynamically typed languages (Jython, Groovy)

Jython – code written in Python, compiled into byte code at runtime, run in JVM

Target of call/parameters need not to be statically known

Units and Quantities (JSR 275) Conversions between many SI/Imperial units JMX 2.0 (JSR 255) Annotations support for def. MBeans JMX Web Service Connector (JSR 262) Native IO - NIO 2.0 (JSR 203) New filesystem API (access file attributes, ...) Async IO Javadoc update (JSR 260) New tags and documentation mechanism Rel. projects – others

Units and Quantities (JSR 275)

Conversions between many SI/Imperial units

JMX 2.0 (JSR 255)

Annotations support for def. MBeans

JMX Web Service Connector (JSR 262)

Native IO - NIO 2.0 (JSR 203)

New filesystem API (access file attributes, ...)

Async IO

Javadoc update (JSR 260)

New tags and documentation mechanism

Java kernel Should be a part of JDK7, but will be released earlier in like “Consumer JRE” in 2008 Small installation of Java Improved installation ? Startup time of JVM ? Tiered compilation Mix of client and server hot spot compiler HotSpot improvements ? Other proposed improvements

Java kernel

Should be a part of JDK7, but will be released earlier in like “Consumer JRE” in 2008

Small installation of Java

Improved installation ?

Startup time of JVM ?

Tiered compilation

Mix of client and server hot spot compiler

HotSpot improvements ?

JDK7 Current build 23 (22 th November) Only bug fixes, no new features OpenJDK Modules (JSR254, JSR257) Projects Beans binding, Fork framework, Swing API Missing! No proposals from EE (mainly app. servers)? Separation of application in JVM What is already implemented?

JDK7

Current build 23 (22 th November)

Only bug fixes, no new features

OpenJDK

Modules (JSR254, JSR257)

Projects

Beans binding, Fork framework, Swing API

Missing!

No proposals from EE (mainly app. servers)?

Separation of application in JVM

Java module system How will it cooperate with OSGi? Java kernel Annotations Static analysis of code How will Google's Android affect Sun's Java? Important for us

Java module system

How will it cooperate with OSGi?

Java kernel

Annotations

Static analysis of code

How will Google's Android affect Sun's Java?

Sun JDK7 Project https://jdk7.dev.java.net/ OpenJDK http://openjdk.java.net/ Overview of Java 7 (updated) http://tech.puredanger.com/java7 Links

Sun JDK7 Project

https://jdk7.dev.java.net/

OpenJDK

http://openjdk.java.net/

Overview of Java 7 (updated)

http://tech.puredanger.com/java7