Tuesday Mar 25, 2014

Learn More About Lambda Expressions

Java SE 8 introduced Lambda Expressions, a powerful new behavior abstraction feature that enables code to be passed around as data. Lambda expressions make your code easier to read, easier to maintain, and less prone to error. Lambda expressions make it possible to express a problem with a higher level of abstraction than was previously possible. Use Lambda Expressions to eliminate large chunks of "boilerplate" code (such as when using inner classes to express behavior), and accomplish more work in less lines of code.

For more information about Lambda Expressions, see the following resources:

See What's New in JDK 8 for information about other new features in JDK 8.

Learn More About New Features in Java SE 8

Java SE 8 introduces significant enhancements to the Java language and class libraries. These enhancements enable you to make code more concise without losing readability; write more reliable code; better utilize multi-core and multi-processor systems (code is no longer inherently serial or parallel); and detect more errors at compile time, rather than at run time.

See What's New in JDK 8 and JDK 8 Adoption Guide for more detailed information on these new features and how to adopt them.

Learn more about these features with the following links from Java SE 8 Technical Documentation:

  • Java Language Enhancements
    • Lambda Expressions enable you to treat functionality as a method argument, or code as data. They are similar to closures and provide more concise anonymous function types and a more functional style of programming.
    • Default Methods (or Extension Methods) provide a mechanism to add new methods to existing interfaces.
    • Type Annotations provide the ability to apply an annotation anywhere a type is used, not just on a declaration.
    • Improved Type Inference enables the Java compiler to takes advantage of target typing to infer the type parameters of a generic method invocation. The target type of an expression is the data type that the Java compiler expects depending on where the expression appears.
    • Obtaining Names of Method Parameters shows you how to retrieve parameter names of methods and constructors (not just types and return types) by reflection.
  • Core Libraries Enhancements
  • Java Virtual Machine Enhancements
    • Nashorn is a lightweight, high-performance JavaScript engine, which is integrated into the JRE.
    • java command lists deprecated and removed options as a result of the retirement of rarely used garbage collection combinations and the removal of permanent generation

Simon Ritter has presented the screencast New Features in Java SE 8: A Developer's Guide during the Java 8 Launch Webcast, which discusses these features.

Download JDK 8 today and try it out!

Monday Mar 24, 2014

Learn More About Streams and Collections

Lambda Expressions are a major new language feature introduced in Java SE 8. Related to that change are the Streams API and Aggregate Operations on Collections. The Collection interface now exposes methods Stream<E> stream() and Stream<E> parallelStream(), for obtaining sequential or parallel streams from an underlying collection.

Here's a quick example showing how this new API (with Lambda Expressions) would be used in place of a traditional Iterator or for loop. It obtains a stream from the underlying collection, selects only red objects, then prints out the name of each object that was matched:

myShapesCollection.stream()
.filter(e -> e.getColor() == Color.RED)
.forEach(e -> System.out.println(e.getName()));

Likewise, you could easily request a parallel stream, which might make sense if the collection is large enough and your computer has enough cores:

myShapesCollection.parallelStream()
.filter(e -> e.getColor() == Color.RED)
.forEach(e -> System.out.println(e.getName()));

Using streams enables your code focus on "what" to do (instead of "how" to do it), leaving the library free to use whatever techniques it deems most appropriate (laziness, out-of-order execution, parallelism, etc.).

For more information on Lambda Expressions and Aggregate Operations, see the following resources:

See What's New in JDK 8 for information about other new features in JDK 8.

Thursday Sep 26, 2013

JavaOne 2013: Designing with Lambda Expressions in Java

On Thursday September 26th, Venkat Subramaniam (President , Agile Developer, Inc.) explained how to implement some elegant design ideas with lambda expressions. His presentation focused on design techniques not from diagrams, but by seeing how to realize the ideas in code.

For more information about lambda expressions in general, see the Lambda Expressions section of the Java Tutorial.

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