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About Bhagvan Kommadi

Bhagvan Kommadi is the Founder of Architect Corner & has around 20 years’ experience in the industry, ranging from large scale enterprise development to helping incubate software product start-ups. He has done Masters in Industrial Systems Engineering at Georgia Institute of Technology (1997) and Bachelors in Aerospace Engineering from Indian Institute of Technology, Madras (1993). He is member of IFX forum,Oracle JCP and participant in Java Community Process. He founded Quantica Computacao, the first quantum computing startup in India. Markets and Markets have positioned Quantica Computacao in ‘Emerging Companies’ section of Quantum Computing quadrants. Bhagvan has engineered and developed simulators and tools in the area of quantum technology using IBM Q, Microsoft Q# and Google QScript. He has reviewed the Manning book titled : "Machine Learning with TensorFlow”. He is also the author of Packt Publishing book - "Hands-On Data Structures and Algorithms with Go".He is member of IFX forum,Oracle JCP and participant in Java Community Process. He is member of the MIT Technology Review Global Panel.

Introduction to Groovy Language

1.Introduction

This is an in-depth article on Groovy language. The examples presented are developed using Groovy. Groovy is an opensource framework for developing and prototyping applications. It is based on java language.

2. Groovy Language Introduction

2.1 Prerequisites

Java 8 is required on the Linux, windows, or Mac operating systems. Groovy version 2.5.7 is used for this article.

2.2 Download

You can download Java 8 from the Oracle web site . Likewise, Groovy 2.5.7 can be downloaded from this website.

2.3 Setup

2.3.1 Java Setup

You can set the environment variables for JAVA_HOME and PATH. They can be set as shown below:

Setup
JAVA_HOME="/desktop/jdk1.8.0_73"
export JAVA_HOME
PATH=$JAVA_HOME/bin:$PATH
export PATH

2.3.2 Groovy Setup

You can set the Groovy home in the PATH as shown below:

Setup
GROOVY_HOME="/usr/local/bin/groovy"
export GROOVY_HOME
PATH=$GROOVY_HOME/bin:$PATH
export PATH

2.4 Running Groovy

You can check the version of the groovy by using the command groovy –version. The command for running Groovy is as below:

Groovy Version
groovy -version

The output of the executed Groovy command is shown below.

Groovy Version Output
apples-MacBook-Air:~ bhagvan.kommadi$ groovy -version
Groovy Version: 2.5.7 JVM: 1.8.0_101 Vendor: Oracle Corporation OS: Mac OS X

2.5 Hello World in Groovy

You can build a helloworld class as shown below in the sample code.

Groovy HelloWorld
package org.javacodegeeks
class HelloWorld 
{
static void main( String [] args) 
{
println("Greetings... ")
}
}

The code above can be executed by using the command below:

Groovy Compilation Command
groovy HelloWorld.groovy

The output of the executed Groovy command is shown below.

Groovy Execution output
apples-MacBook-Air:groovy bhagvan.kommadi$ groovy HelloWorld.groovy
Greetings... 

2.6 Groovy IDE Integration

You can configure the Groovy Eclipse plugin from the distribution site. The screen shot below shows the configuration of Groovy Eclipse plugin from Help-> Install-> New Software.

The groovy version is set from Eclipse’s Preferences -> Groovy ->Compiler. The setting of the groovy version 2.4.16 is shown below:

groovy language - Groovy Eclipse
Groovy Eclipse
groovy language - Groovy Version
Groovy Version- Eclipse

2.7 Groovy Data Types

Groovy has different data types such as :

  • Byte
  • Short
  • int
  • long
  • float
  • double
  • char
  • Boolean
  • String

You can try out different data types as shown below in the sample code.

Groovy DataTypes
package org.javacodegeeks
class DataTypes {
   static void main(String[] args) {
    
      int x = 6;


      long y = 200L;

    
      float a = 30.56f;

    
      double b = 20.5e40;

     
      BigInteger bi = 20g;

     
      BigDecimal bd = 4.5g;

      println(x);
      println(y);
      println(a);
      println(b);
      println(bi);
      println(bd);
   }
}

The code above can be executed by using the command below:

Groovy Compilation Command
groovy DataTypes.groovy

The output of the executed Groovy command is shown below.

Groovy Execution output
apples-MacBook-Air:groovy bhagvan.kommadi$ groovy DataTypes.groovy 
6
200
30.56
2.05E41
20
4.5

2.8 Groovy Variables

In groovy, variables are declared using def keyword. Sample code is attached below.

Groovy Variables
class VariableExample {
   static void main(String[] args) {

      int y = 7;
      int Y = 8;
      def _Person = "John";
      println(y);
      println(Y);
      println(_Person);
   }
}

The code above can be executed by using the command below:

Groovy Compilation Command
groovy VariableExample.groovy

The output of the executed Groovy command is shown below.

Groovy Execution output
apples-MacBook-Air:groovy bhagvan.kommadi$ groovy VariableExample.groovy 
7
8
John

2.9 Groovy Methods

2.9.1 Groovy Static Methods

In groovy, static methods are defined using static and def keywords. The sample code is shown below.

Groovy Methods
class MethodsExample {
   static def ExecuteMethod() {
      println("Executing in groovy");
      println(" a static method");
   } 
	
   static void main(String[] args) {
      ExecuteMethod();
   } 
}

The code above can be executed by using the command below:

Groovy Compilation Command
groovy MethodsExample.groovy

The output of the executed Groovy command is shown below.

Groovy Execution output
apples-MacBook-Air:groovy bhagvan.kommadi$ groovy MethodsExample.groovy 
Executing in groovy
 a static method

2.9.2 Groovy Instance Methods

In groovy, instance methods are created like in java. The example below shows how to create the instance methods.

Groovy Methods
class InstanceMethods { 
   int y; 
	
   public int getY() { 
      return y; 
   } 
	
   public void setY(int pY) { 
      y = pY; 
   } 
	
   static void main(String[] args) { 
      InstanceMethods instance = new InstanceMethods(); 
      instance.setY(200); 
      println(instance.getY()); 
   } 
}

The code above can be executed by using the command below:

Groovy Compilation Command
groovy InstanceMethods.groovy

The output of the executed Groovy command is shown below.

Groovy Execution output
apples-MacBook-Air:groovy bhagvan.kommadi$ groovy InstanceMethods.groovy 
200
apples-MacBook-Air:groovy bhagvan.kommadi$

2.9.3 Groovy Method Parameters

Method parameters in groovy are defined as presented in the code below.

Groovy Methods
class MethodParamExample {
   static void product(int a,int b) {
      int c = a*b;
      println(c);
   }  
	
   static void main(String[] args) {
      product(20,6);
   } 
}

The code above can be executed by using the command below:

Groovy Compilation Command
groovy MethodParametersExample.groovy

The output of the executed Groovy command is shown below.

Groovy Execution output
apples-MacBook-Air:groovy bhagvan.kommadi$ groovy MethodParametersExample.groovy 
120
apples-MacBook-Air:groovy bhagvan.kommadi$

2.10 Groovy File I/O

Groovy has features to read, write, and traverse files. The sample code shows how to read a file in groovy.

Groovy File I/O
import java.io.File 
class FileIO { 
   static void main(String[] args) { 
      new File("input.txt").eachLine {  
         line -> println "line : $line"; 
      } 
   } 
}

The code above can be executed by using the command below:

Groovy Compilation Command
groovy FileIO.groovy

The input file (input.txt) contents are shown below.

input.txt
line1
line2
line3

The output of the executed Groovy command is shown below.

Groovy Execution output
apples-MacBook-Air:groovy bhagvan.kommadi$ groovy FileIO.groovy
line : line1
line : line2
line : line3

2.11 Groovy Strings

In groovy, a String literal is defined as text in quotes. The example code is shown below.

Groovy File I/O
class StringOperations {
   static void main(String[] args) {
      String c = "Christmas";
      String d = "Greetings";

      println(d.length());		
      println(c + d);
   }
}

The code above can be executed by using the command below:

Groovy Compilation Command
groovy StringOperations.groovy

The output of the executed Groovy command is shown below.

Groovy Execution output
apples-MacBook-Air:groovy bhagvan.kommadi$ groovy StringOperations.groovy 
9
ChristmasGreetings

3. Download the Source Code

That was an introduction to Groovy Language.

Download
You can download the full source code of this example here: Introduction to Groovy Language

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