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Groovy...

  • is an agile and dynamic language for the Java Virtual Machine
  • builds upon the strengths of Java but has additional power features inspired by languages like Python, Ruby and Smalltalk
  • makes modern programming features available to Java developers with almost-zero learning curve
  • supports Domain-Specific Languages and other compact syntax so your code becomes easy to read and maintain
  • makes writing shell and build scripts easy with its powerful processing primitives, OO abilities and an Ant DSL
  • increases developer productivity by reducing scaffolding code when developing web, GUI, database or console applications
  • simplifies testing by supporting unit testing and mocking out-of-the-box
  • seamlessly integrates with all existing Java classes and libraries
  • compiles straight to Java bytecode so you can use it anywhere you can use Java

Experience Groovy 1.8

Groovy 1.8 is the latest major and stable version of the popular dynamic language for the JVM. To learn more about the novelties, make sure to read the release notes. In a nutshell, Groovy 1.8 provides new Domain-Specific Language authoring capabilities for more readability and expressivity of your business rules, runtime performance improvements, the bundling of the GPars parallel and concurrency library, built-in JSON support, new compile-time meta-programming features (several new useful AST transformations), new functional programming aspects for closures, and much more.


"Groovy is like a super version of Java. It can leverage Java's enterprise capabilities but also has cool productivity features like closures, builders and dynamic typing. If you are a developer, tester or script guru, you have to love Groovy."

Samples

A simple hello world script:

def name='World'; println "Hello $name!"

A more sophisticated version using Object Orientation:

class Greet {
  def name
  Greet(who) { name = who[0].toUpperCase() +
                      who[1..-1] }
  def salute() { println "Hello $name!" }
}

g = new Greet('world')  // create object
g.salute()               // output "Hello World!"

Leveraging existing Java libraries:

import static org.apache.commons.lang.WordUtils.*

class Greeter extends Greet {
  Greeter(who) { name = capitalize(who) }
}

new Greeter('world').salute()

On the command line:

groovy -e "println 'Hello ' + args[0]" World

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11 Comments

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  1. Apr 23, 2008

    Vimal Kansal

    Hi,

    I am unable to get the example that you have posted on InfoQ for using the tripple dot notation of variable args list. i.e I cut and pasted the following code

    into groovyconsole and I get the following:

    Exception thrown: org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed, Script14: 1: unexpected token: ... @ line 1, column 21.
1 error

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed, Script14: 1: unexpected token: ... @ line 1, column 21.
1 error

    Am I missing something?

    Thanks

    Vimal 

  2. Apr 23, 2008

    Viktor Hugo Morales

    Vimal,

    I tried it, but now i get another error:

    groovy.lang.MissingMethodException: No signature of method: java.lang.Integer.size() is applicable for argument types: () values: {}
	at Script14.sum(Script14:3)
	at Script14.run(Script14:8)

  3. Apr 23, 2008

    Paul King

    Vimal, try this:

  4. Oct 13, 2008

    jamesqiu

    Oh，in Groovy1.6.0b2,  following line CAN'T run:

    $groovy -e "println 'Hello ' + args[0]" World

    Caught: groovy.lang.MissingPropertyException: No such property: args for class: script_from_command_line
    at script_from_command_line.run(script_from_command_line:1)

    It's just on groovy's HOMEPAGE !

  5. Oct 14, 2008

    Guillaume Laforge

    James, this is a known problem, and a JIRA issue was raised.

    This regression will be fixed for Groovy 1.6-rc-1.

    Sorry for the inconvenience.

  6. Oct 31, 2008

    jamesqiu

    Thanks glaforge.  I've fixed my Groovy 1.6b2 with your method. Open source is great!

  7. Apr 08, 2009

    redstun

    What about shortening the names for things in Groovy? like Maven has the mvn command.

     E.g.

    groovy => gv

    groovyc => gvc

    groovysh => gvsh

    groovlet script => gvp (isn't it sort of  jsp like stuff?)

    ... 

    (then rewrite the old ones to call the new-names for backward compatibility)

  8. Sep 24, 2009

    Patricia Shannon


    (9/24/2009 - fixed blog so that the linked entry displays properly in web browser)

    There are times when we need to read a single record at a time from a file.
    Eg., if we want to stop reading a file at a certain point.
    Or when working with more than one file. After comparing records, one might have to read a record from one or the other file, or from both.

    I was not able to find good documentation on how to do this.
    By spending a lot of time searching and experimenting, I was able to find out how to do it.

     see http://patriciashannon.blogspot.com/2009/09/groovy-how-to-read-one-line-at-time.html

     Note that it requires two executions of .readLine for each record, but that is easy to get around, but putting it in a closure, as shown. This would usually be done anyway, to include things like record counts and end-of-file logic. So in a real program, each readALine closure would have two readLine statements.

  9. Sep 26, 2009

    Patricia Shannon

    When I put the following in my initialization routine, highValue was undefined elsewhere
         String highValue = '\377'

    So I changed the code to the following two lines, which worked
         String highValue2 = '\377'
         highValue = highValue2

    When I replaced these two lines by the following, it was again undefined elsewhere
         public String highValue = '\377'

    Is there a way to define a global typed variable with a single statement?

  10. Sep 26, 2009

    Patricia Shannon

    How can I put in code like Paul King did, which is enclosed in a box?

    When I tried copying a short closure from a program, I can an error msg because something (?web browser) tried to execute it.

  11. Aug 15, 2010

    wonder365

    This page is ugly, As a firstview of Groovy, It's too long to see.  anybody helps to fix it?