Emerging languages series - Groovy

Our favorite Java is getting some serious competition in recent years , It seems there are more than 200 languages that target Java platform.
There is growing interest in languages like Scala, Groovy , Clojure , JRuby, Jython for their features and simplicity. Out of this lot we will take a close look at Groovy today as its getting wide attention in the market over recent years.

Why Groovy ?

• Groovy is more or less a superset of Java
• Builds upon the strengths of Java but has additional power features inspired by languages like Python, Ruby and Smalltalk
• Could seamlessly switch back and forth between Java and Groovy 
• Considered simpler and easier to learn over Jython and JRuby
• Groovy has Java-like syntax and hence the learning curve is not steep.
• Simplifies testing by supporting unit testing and mocking out-of-the-box

Once you install Groovy, you could straightaway start programming in Groovy,  just put your Groovy jar file along with your application and get the program working in any machine.

There are many online editors and IDE plugin available to compile and run your Groovy code.

So what is Groovy ?

James Strachan conceived the idea of Groovy language and started development in 2003.

Groovy is a dynamic language that dynamically compiles the code to the Java platform. It is popular as a scripting language and also widely used for unit testing Java code. Groovy is open source (Apache v2 license) and is backed by VMware.

The current stable release is Groovy 2.2. You can use Groovy in most common operating systems like Linux, Windows, and Mac. 

Let’s see how Groovy looks better Java with few examples –

Hello World Example –

// Java

class HelloWorld {

public static void main(String []args) {

System.out.println("Hello world");

}

}

// Groovy

println("hello world")

More Detailed Examples –

Let’s take a look at collection (map) processing example. Lets create a map and do some processing in both Java and Groovy.

// Java

Map worldCapitals = new HashMap<>();

worldCapitals.put("England", "London");

worldCapitals.put("Japan", "Tokyo");

worldCapitals.put("France", "Paris");

worldCapitals.put("Italy", "Rome");

worldCapitals.put("USA", "Washington");

for(Map.Entry capital : worldCapitals.entrySet()) {                       

System.out.printf("%s => %s \n", capital.getKey(), capital.getValue());

}

// Groovy

def worldCapitals =   [ "England" : "London",

"Japan" : "Tokyo", 

"France" : "Paris",

"Italy" : "Rome",

"USA" : "Washington" ]

worldCapitals.each {

key, value ->  

println "$key = $value" 

}

In this case Groovy provides a simple array-like syntax for the Map data structure. See how use of each() method closure makes it simple to write the code.

We all know how we write custom code to sort a map by value in Java but the same can be achieved in a line with Groovy. See below -

def sortedMap = worldCapitals.sort { it.value }

sortedMap.each {

key, value ->  

println "$key => $value" 

}

In above Groovy code, we just passed the it.value (current iterator’s value) to the sort method. With the power of closures, the code became much simple and readable.

Groovy provides a higher-level abstraction to this functionality, and hence the code is much simpler.

Tip - The soon to be released Java 8 has also introduced concept of closures in form of  "lambda expressions". It will be interesting to see how Java is incorporating these new age language features in their new release. I will write separate post to cover Java 8 features and capabilities soon.

XML Generation Example -

In general it’s very common to generate structured output like HTML , XML or JSON in Java code. So let’s see one example around this piece.

// java

PrintWriter pw = new PrintWriter(new FileWriter("/capitals.xml"))

pw.println("");

for(Map.Entry capital : worldCapitals.entrySet()) {                  

pw.printf("\t \n \t\t '%s' \n \t \n", capital.getKey(), capital.getValue());

}

pw.println("

");

// Groovy

def capitals =   [ "England" : "London",

"Japan" : "Tokyo", 

"France" : "Paris",

"Italy" : "Rome",

"USA" : "Washington" ]

xmlbuilder = new groovy.xml.MarkupBuilder()

xmlbuilder.worldcapitals {

capitals.each {

key, value ->

country(name:key) { capital(value) }

}

}

Now just see how simple it is to do the same thing with Groovy with lot of readability. Groovy supports builders (based on Builder design pattern) for creating HTML and XML files.

Take away from this comparison -

• Traversing a data structure is easy in Groovy - you can use “closures” instead of plain loops and use each() method. 
• Groovy is high on meta-programming and regular expression handling capabilities.
• Groovy builders are fabulous if you dealing with HTML , XML , JSON etc.
• Better for productivity and code readability for sure
• Being a dynamic language Groovy is an excellent candidate for creating DSLs (Domain Specific Languages)

We have just tried to explore few basic features of Groovy here. You should explore further programming improvements such as automatic check for nulls, helper methods, embedded expressions in strings, and operator overloading. One should also explore its meta-programming and regular expression handling capabilities.

You’ll find Grails web framework and Groovy Server Pages (GSP) interesting if you are a serious web-developer. If you are an admin, you may find Gradle build automation framework useful. Grails framework (that is similar to Ruby on Rails) is built on top of powerful and popular frameworks such as Spring and Hibernate.

Resources to learn further –

Groovy Documentation - http://groovy.codehaus.org/Documentation

Groovy Eclipse plugin - http://groovy.codehaus.org/Eclipse+Plugin

Programming Groovy 2 - Dynamic Productivity for the Java Developer, By Venkat Subramaniam

Groovy in Action, By Dierk Koenig, Andrew Glover, Paul King, Guillaume Laforge, Jon Skeet

If you are a developer, tester or script guru, you have to love Groovy. So keep grooving and have fun with it !!