OpenJDK Java8 Lambda Syntax

This document provides some working examples of the future OpenJDK 8 lambda syntax.   There was a lot of discussion whether the language changes would get included in the Java7 or Java8 so it looks like we will see the changes in Java8 slated for release in 2013.

The lambda conversion uses a target SAM type or single abstract method.

You can see the conversion in this example:

    interface F {
        void f();
    }


        final F func = () -> System.out.println("Test");
        System.out.println("Function Object : " + func);
        func.f();
...
The variable type on the left is an interface of type 'F' with a single method 'f'.

It seems that the Java lambda implementation provides a slightly more expressive syntax for code blocks that you would normally see in an anonymous inner class.  These sections of  code are synonymous.

        for (int i = 0; i < 10; i++) {
            final int ii = i;
            final int res6 = ((Fx)( (final int y) -> y + ii )).f(10);          
            System.out.println("[6] Output from recent lambda call index="+i+" : " + res6);
        }
        ...

        for (int i = 0; i < 10; i++) {
            final int ii = i;
            // @line70, anon inner class call
            final Fx fxx = new Fx() {
              public int f(int y) { return y + ii; }
            };
            final int res6 = fxx.f(10);          
            System.out.println("[7] Output from anonymous inner call index="+i+" : " + res6);
        }


Resources:


The Lambda team provided a binary build of Javac and Java for Windows and Linux.

[1] http://jdk8.java.net/lambda/


$ ./java.bat
openjdk version "1.8.0-ea"
OpenJDK Runtime Environment (build 1.8.0-ea-b1314)
OpenJDK Client VM (build 23.0-b04, mixed mode)

https://github.com/berlinbrown/BuildingOpenJDKCookbook

BuildingJDK8/ExampleLambdaProject/LambdaJava8Test.java


http://hg.openjdk.java.net/lambda/lambda/

http://mail.openjdk.java.net/pipermail/lambda-dev/attachments/20100122/3764c21a/attachment.txt

----

The Thoracic system may be compared to a great freight system, with each of its tributaries[Pg 218]—from the main trunk arteries down to the tiniest blood vessels—starting from the heart and carrying its cargo of blood to every part of the body by means of the power furnished by the lungs.



Comments

Post a Comment

Popular posts from this blog

Is Java the new COBOL? Yes. What does that mean, exactly? (Part 1)

Image
"If you want to know the past, look at your present. If you want to know the future, look at your present." -- Gautama Buddha Java is the new COBOL, whaaaat?     If you are software developer that mainly writes applications for the web; even if you aren't a Java/J2EE developer, you have probably heard the new meme circulating the web and blogosphere. "Java is the new COBOL" . Most blogs and technical writers regurgitate that statement and follow-up by saying that EJBs suck, and some companies are considering Ruby on Rails. I didn't really think much of these posts. I get the impression that a lot of these "managers" don't write any Java or COBOL code. They are really not highlighting the seriousness of the problem. COBOL development has remained stagnant for decades. Java may see the same problem in the future. The Pentagon/DOD has a trillion dollar COBOL problem because it is so difficult to change their ancient infrastructure. Anyon
Read more

On Unit Testing, Java TDD for developers to write

It has been a while, let's kick off 2017 with a blog entry. I have read and I am reading about four or five posts a day about unit testing. It really has been a long time obsession for me. I have moved past the technical and practical considerations on unit testing frameworks and done with the debates with "should you use Junit or Mockito or Karma?" I am more interested in the psychology of unit testing, who does it, likes it, hates it? It really is one of those easy to learn, hard to master concepts. For example, many many may play chess when they are young and can end up being horribly chess players most of their life, I am part of that majority. Unfortunately, I have never played chess and sat down for hours and tried to master it. I never see the common patterns or have a developed end game. I mostly just play with a knowledge of the basic rules. Following good unit testing practices within your software development shop is a lot like playing chess. It is easy to le
Read more

JVM Notebook: Basic Clojure, Java and JVM Language performance

Image
"Measure, don't guess. The primary goal of all performance tuning exercises should be maximize the end user experience given the resource constraints." [1] "It isn't so much a "farewell to the J" as an expansion of the platform opportunities Java provides. Sun's investment to power ongoing development of JRuby and Jython broadens the range and reach of Java, as a whole." -- Rick Ross Overview and JVM Languages    One of the exciting trends to recently emerge from the Java community is the concept of the JVM language. These technologies are all that you would expect them to be. They are implementations of languages that run on the Java Virtual Machine. Some are newly created and some are based on existing, more mature languages. JRuby, Jython are two JVM languages based on CRuby and CPython. Groovy, Scala, Clojure are three completely new JVM languages that were created to add new language features that weren't supported by the core Ja
Read more