Book Image

Groovy 2 Cookbook

Book Image

Groovy 2 Cookbook

Overview of this book

Get up to speed with Groovy, a language for the Java Virtual Machine (JVM) that integrates features of both object-oriented and functional programming. This book will show you the powerful features of Groovy 2 applied to real-world scenarios and how the dynamic nature of the language makes it very simple to tackle problems that would otherwise require hours or days of research and implementation. Groovy 2 Cookbook contains a vast number of recipes covering many facets of today's programming landscape. From language-specific topics such as closures and metaprogramming, to more advanced applications of Groovy flexibility such as DSL and testing techniques, this book gives you quick solutions to everyday problems. The recipes in this book start from the basics of installing Groovy and running your first scripts and continue with progressively more advanced examples that will help you to take advantage of the language's amazing features. Packed with hundreds of tried-and-true Groovy recipes, Groovy 2 Cookbook includes code segments covering many specialized APIs to work with files and collections, manipulate XML, work with REST services and JSON, create asynchronous tasks, and more. But Groovy does more than just ease traditional Java development: it brings modern programming features to the Java platform like closures, duck-typing, and metaprogramming. In this new book, you'll find code examples that you can use in your projects right away along with a discussion about how and why the solution works. Focusing on what's useful and tricky, Groovy 2 Cookbook offers a wealth of useful code for all Java and Groovy programmers, not just advanced practitioners.
Table of Contents (17 chapters)
Groovy 2 Cookbook
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

Filtering a text file's content


Filtering a text file's content is a rather common task. In this recipe, we will show how it can be easily achieved with Groovy.

Getting ready

Let's assume we want to filter out comment lines from a Bash script stored in the script.sh file and we want to save it into the new_script.sh file. First of all, we need to define two variables of the java.io.File type that point to our inputFile and outputFile:

def inputFile = new File('script.sh')
def outputFile = new File('new_script.sh')

How to do it...

File filtering can be implemented in several ways:

  1. We can make use of the closure-based methods (that is eachLine and withPrintWriter) that we have got familiar with in the Reading a text file line by line and Writing to a file recipes:

    outputFile.withPrintWriter { writer ->
      inputFile.eachLine { line ->
        if (!line.startsWith('#')) {
          writer.println(line)
        }
      }
    }
  2. Another way to achieve the same result is to use a filterLine method. It takes a Writer and...