Monday Sep 23, 2013

The JavaOne 2013 Technical Keynote

by Timothy Beneke

Mark Reinhold, Oracle’s Chief Architect, the Java Platform Group, took the stage to kick off Sunday’s technical keynote at the Moscone Center. He began by quoting “father of Java” James Gosling. For Java to thrive, it must maintain what Gosling called the “feel of Java”. In other words, it must retain the key values of readability, simplicity, and universality.

“If we keep those,” said Reinhold, “then Java will remain not just productive but fun. It is not enough to simply add popular features each year.”

Lambda Expressions – The Single Largest Upgrade Ever
He turned to lambda expressions, which he described as the single largest upgrade to the programming model ever -- larger even than generics. “This is the first time we have done a carefully coordinated co-evolution of the JVM, the language, and the libraries all together – and the results still feel like Java,” said Reinhold.

He then welcomed Oracle Java Language Architect, Brian Goetz, to share the stage and began by remarking that while most developers understand that lambda offers a simple way to express code as data, some are not sure how it helps Java. Goetz responded that lambda expressions would more than help Java. “It’s going to change the way we all program in Java every day,” he explained. “Programming well is about finding the right abstractions. We want the code we write to look like the problem statements it’s trying to solve, so we can look at it and immediately know it’s correct. Java has always given us good tools for abstracting over data types. I wanted to do better in abstracting over patterns of behavior – that’s where lambda comes in.”

He illustrated this with some simple code that was, strictly speaking, “good” code, but weighed down with boilerplate and did not read like the problem statement it was trying to solve. It could be improved by using an inner class tool, but that too generated a lot of boilerplate. Reinhardt pointed out that improving the code made it less pleasant to work with, as if the developer was being punished for doing the right thing. This often causes developers to give up and do it the “dumb and ugly way”.

Lambdas can replace inner classes with a lambda expression which is simply an anonymous method that captures a behavior without a lot of syntactic boilerplate. “Lambdas are a nicer syntax,” said Goetz. “But they are also something deeper. It’s not just a compiler generating inner classes for you – it uses the invokedynamic feature to get more compact and higher performance code. It will make a qualitative difference in the way we program.”

If the right way to write a program is unpleasant, then people are less likely to do it according to Goetz. They are more tolerant of doing it the wrong way. He gave an example of how lambda expressions address this with the collections API involving a new abstraction to the JDK called stream and showed how to represent a simple query through applying a filter and mapping transformation, followed by an aggregation, in a way that is fused into one path without creating any intermediate weapons.

Reinhold summarized the key points: “So lambda brings 3 weapons to Java – syntax, performance and abstraction.”

“Plus parallelism,” Goetz added. He explained that Java 7 has the fork/join framework for parallel decomposition that is powerful, flexible, and highly efficient – but not the easiest thing to use. Goetz showed how lambdas enable better parallelism without needing to write fork join code: by asking the collection for a parallel stream it uses fork/join under the hood.

Lambda also helps with normal sequential code by making code clearer, less noisy, and easier to read. “When you have code that is hard to read, that’s where bugs come from. You are trying to maintain some code, you look at the code and think you know what it does, but don’t actually know what it does, and boom! – you’ve introduced a bug.”

All in all, the message was clear: Lambda expressions make Java code easier to read and easier to write.

Working with Lambda and the Collections Framework
For lambdas to be successful, they must work with the Java Collections Framework, which is now 15 years old. So an evolution of the interface was in order. Goetz’s team had to grow an interface over time without breaking implementations of the interface. They added a concept that allows developers to compatibly add a method to an interface, as long as a default implementation is provided.

Reinhold remarked that he has now written a couple of thousand lines of code with lambda features and really enjoyed it. “I can be more productive, and the end result still feels like Java,” he said.

To get started learning lambda expressions, Java developers can go to the OpenJDK Project Lambda page and download the developer preview builds there.

Reinhold reminded attendees that there is a great deal more in Java SE 8 besides lambda expressions. Developer preview builds can be downloaded at JDK8.java.net. “Now is a great time to download JDK 8 and take it for a spin. Every planned feature is in there. It’s reasonably stable and it passes almost all of the tests. If you have any feedback, please send it in!” said Reinhold. 

Playing Chess
In the rest of the technical keynote, Oracle’s John Ceccarelli, head of engineering for Oracle’s NetBeans team and Oracle’s JavaFX architect Jasper Potts, arrived on stage to demonstrate a Duke pad running real Java via a chess program that was connected to a server. The iPad operated through an HTML5 client talking to a Java EE 7 back end with an EE server in charge of  messaging, communication, game state, and so on, with clients hook into it – all built with NetBeans. Jasper Potts further showed off the chess demo with an HTML5 client using a front end to a chess server that was managing the chess games. Then a robot, powered by Java ME 8, took over the game.

Oracle Software Engineer, Santiago Pericas Geertsen, who built the chess server, also described how it was built with 5 distinct functional modules.

In sum, attendees witnessed a server running Java EE 7 hooked up with a variety of clients, some written in HTML5, one written in JavaFX on a Duke pad, one using JavaFX 3D on a powerful laptop, plus a Java ME 8-powered robot contributing to the ongoing chess game. In the process, the powers of the Raspberry Pi were demonstrated.

Developers were encouraged to jump in the water, go for a swim, and have fun with NetBeans and Java embedded.

Java SE 9 and Beyond
Wrapping it up, Reinhold peered a bit into the future and suggested some possible directions for Java, some of which are already in development:

One is Java on GPUs, graphic processing units. As GPUs are being used more and more widely to process big data he suggested that it would be good to make Java work directly with the GPU rather than having to call out to some primitive interface. An OpenJDK called Sumatra has people working on this.

Reinhold spoke of the need for reification. Java’s generics, added in 2004, are based on the notion of erasure for good technical reasons as a sound way to create a type system that supports migration compatibility. But this creates programming problems in which the erasure approach severely limits what can be expressed. Reinhold suggested that introducing some reification and eliminating the “annoying dichotomy between primitive and reference types” would be of value.

He mentioned JNI 2.0 and said, “It just shouldn’t be so hard to integrate Java with native code after all these years.”

He called for memory efficient data structures: “As we get into big data – all this boxing and pointer chasing makes it hard to do big data well. We could have less boxing and pointer chasing and load a lot more data into memory.”

Finally, he talked about the notion of a truly modular platform. “The compact profile in Java 8 is a start but it is not flexible enough. We need to continue to unify the Java SE and Java ME platforms.”

JDK 8

OpenJDK Project Lambda

Watch Keynote and Session Highlights on Demand

Wednesday Aug 07, 2013

Garbage First Garbage Collector Tuning

A new article, now up on otn/java, titled “Garbage First Garbage Collector Tuning,”
by Monica Beckwith, Principal Member of Technical Staff at Oracle, and performance lead for the Java HotSpot VM's Garbage First Garbage Collector (G1 GC), shows how to adapt and tune the G1 GC for evaluation, analysis, and performance.

As Beckwith explains, the Garbage First Garbage Collector is the low-pause, server-style generational garbage collector for Java HotSpot VM. It uses both concurrent and parallel phases to achieve its target pause time and maintain good throughput. A garbage collector is a memory management tool. When G1 GC determines that a garbage collection is necessary, it first collects the regions with the least live data – known as garbage first.

Beckwith describes the collection phases and marking cycles, lists default tuning devices, offers recommendations about how to fine tune and evaluate garbage collection, and shows how to respond to overflow and exhausted log messages.

She concludes her article as follows:

“G1 GC is a regionalized, parallel-concurrent, incremental garbage collector that provides more predictable pauses compared to other HotSpot GCs. The incremental nature lets G1 GC work with larger heaps and still provide reasonable worst-case response times. The adaptive nature of G1 GC just needs a maximum soft-real time pause-time goal along-with the desired maximum and minimum size for the Java heap on the JVM command line.”

Check it out here.

Tuesday Jul 24, 2012

The JVM Language Summit - 2012

A new article, now up on otn/java, provides information about the upcoming 2012 JVM Language Summit, scheduled for July 30–August 1, 2012 on the Oracle campus in Santa Clara. The Summit brings together top language designers, compiler writers, tool builders, runtime engineers, and VM architects, from around the world for an open technical collaboration.

Summit organizer Brian Goetz of Oracle remarks: "We've been running the JVM Language Summit for the past five years. The attendees at the Summit are the people who are making languages on the JVM happen—there are typically architect-level representatives from many JVM language communities including JRuby, Jython, Scala, Groovy, and Clojure. This is a tremendous opportunity for the community to influence the future direction of the JVM and for us to learn more about how the JVM is being used, where it shines, and where it falls short."

The schedule is equally divided between traditional presentations, most of which are limited to 40 minutes, and informal workshops, which consist of small facilitated discussion groups among self-selected participants to enable deeper dives into the subject matter. There will also be impromptu lightning talks.

Learn more here.


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