Groovy Goodness Notebook
Groovy Goodness Notebook
Experience the Groovy programming language through code snippets
About the Book
In 2009 I started to write small blog posts about Groovy at Messages from mrhaki. The posts contained code samples of cool Groovy features I just didn't want to forget. The blog posts turned out to be a useful resource for people learning and using Groovy in their every day programming.
The Groovy Goodness Notebook contains the blog posts about Groovy previously mentioned on my blog. The posts have been edited slightly so they can be used for the book. The book gives a broad overview of all the great features we can find in the Groovy language.
Updated on February 1st 2016 to include the following new subjects:
- Inspect Method Returns Nicely Formatted Object Values
- Operator Overloading in Reverse
- Removing Elements From a Collection
- Change Directory For Saving Dependencies Grape
- See More Info About Downloading With Grape
- Exclude Transitive Dependencies With Grape
- IntelliJ IDEA Intentions For String Values
- Turn Map Into Class With IntelliJ IDEA
- Turn Method Parameters Into Named Map Arguments With IntelliJ IDEA
- Defining Public Accessible Constant Fields
- Customise Groovydoc Output With Gradle
- Customising The Groovy Compiler
The book categorizes the posts into the following sections:
- Syntax
- Operators
- Numbers
- Strings
- Regular Expressions
- Dates
- Lists, Ranges and Arrays
- Maps
- Closures
- SQL
- Files, Reades, Writers and URls
- XML and JSON
- AST transformations
- Metaprogramming
- DSL and Builder Support
- Scripts
- Testing
- Miscellaneous
About the Author
Bundles that include this book
Table of Contents
- About Me
- Introduction
-
Syntax
- Default Imports
- Semicolons are Optional
- Optional return Keyword
- Automatic Return Value Casting
- Static Imports
- Optional Parenthesis
- Check for Object Equality
- Using def to Define a Variable
- Using Lists and Maps As Constructors
- Parameters with Default Values
- Named Parameters are Converted to Map
- Use a Map as Interface Implementation
- MultiMethods or Multiple Dispatch
- Multiple Overloaded Operator Methods for Nice API
- Operator Overloading in Reverse
- Exception Handling
- The With Method
- The Switch Statement
- Use Map in Switch Statement
- Tell the Groovy Truth
- We Can Handle the Truth
- Groovy Truth for Simple Type Arrays
- Boolean Implications
- The as Keyword
- Define Your Own Type Conversion
- Using Project Coin Features Also With Older Java Versions
- Getting and Setting Properties
- GroovyBeans: the Simpler JavaBeans
- Powerful Assert
- Multiple Assignments
- Multiple Assignments Revisited
- Turn Methods into Closures
- Use Keywords as Method Names
- Chaining Traits
- Implementing Traits at Runtime
- Using Implicit call() Method
- Groovy Mystic Expressions
- Invoke Methods Dynamically
- Create Class Instance Dynamically
- Know More About a Class
- Getting Information About Objects
- Get Hints About Missing Methods or Properties
- Executing String or List
- Run Code at a Specified Time
- Using AntBuilder
- Add a ShutdownHook
- Use a Class by Proxy
- Defining Public Accessible Constant Fields
-
Operators
- Safe Navigation to Avoid NullPointerException
- The Elvis Operator ?:
- The Spaceship Operator
- The Spread-Dot Operator
- The Spread Operator
- Are You In? (Membership Operator)
- Is Object in Class Hierarchy
-
Numbers
- BigDecimal
- Round and Truncate Decimal Values
- Integer Divisions
- Make a Number Absolute
- Raising the Power of Numbers
-
Strings
- String.multiply()
- ‘String’, “Strings”, /Strings/ and GStrings
- New Dollar Slashy Strings
- Get to Know More About a GString
- Check if String is a Number
- What Character Are You?
- Access Strings with Subscript Operator
- Capitalize Strings
- Base64 Encoding
- Check if a String Only Contains Whitespaces
- Convert String to Boolean
- Padding Strings
- Working with Lines in Strings
- Using the replaceAll Methods from String
- Replace Characters in a String with CollectReplacements
- Text Translation
- Remove Parts of a String
- Remove Part of String With Regular Expression Pattern
- Splitting Strings
- Get Unique Characters in a String
- Partial Matches
- Transform String into Enum
- String Continuation
- Strip Leading Spaces from Lines
- Strip Leading Spaces from Lines with Margin
- Formatted Strings with sprintf
- Expand or Unexpand Space or Tab Delimited Text
- Normalize and Denormalize Linefeeds and Carriage Returns
- Converting Byte Array to Hex String
- GString as Writable
- Closure as Writable
-
Regular Expressions
- Using Regular Expression Pattern Class
- Matchers for Regular Expressions
-
Dates
- Working with Dates
- Setting Date and Calendar Values with Subscript Operators
- Convert Date to java.sql.Timestamp
- Convert Date to Calendar
- Format Dates with TimeZone
- Parse Date.toString() Value
- Use the set Method to Define a Date or Calendar Value
- Create New Date from Old Date with Updates
- Create New Date or Calendar from Existing and Set Property Value
- Clear Time Portion of a Date
- Date and Time Durations and the TimeCategory
- Loop Through Date and Calendar Ranges
-
List, Ranges and Arrays
- Create Elements in Collection Definition
- Finding Data in Collections
- Find First Non-Null Result From a Closure
- Find Non-Null Results After Transformation in a Collection
- Find Elements Matching Groovy Truth
- Removing Elements From a Collection
- Use Ranges as Subscript Operators
- Use Strings as Subscript Operator
- Using the Subscript Operator on Iterators
- Looping in Different Ways
- Keep Your Values in Ranges
- Getting the Tail of a List
- Getting Head And Tail From an Array of Objects
- Getting the First and Last Element of an Iterable
- Getting All But the Last Element in a Collection with Init Method
- Take and Drop Items from a List
- Drop or Take Elements with Condition
- Take Or Drop Last Items From a Collection
- Getting the Indices of a Collection
- Combine Elements Iterable with Index
- Pop And Push Items In a List
- Apply Method to All Elements in a List
- Apply Closure to All Element in a Collection with collect
- Use Collect with Initial Collection Value
- Transform Collection to a Map with collectEntries
- Transform Items into a Collection with collectMany
- Collect on Nested Collections
- Recursively Collect Elements
- Join Elements to a String
- Using the Inject Method
- Using the GroupBy Method
- GroupBy with Multiple Closures
- Removing Duplicate Elements in a Collection
- Sort or Remove Duplicates without Changing the Original Collection
- New Methods to Sort and Remove Duplicates From Collection
- Using the OrderBy Comparator
- GroovyCollections Utility Class
- Splitting with Closures
- Intersect Collections
- Collate a List into Sub-lists
- Getting All Subsequences of a List
- Looping Through Each Permutation in a Collection
- Counting the Items in a List
- Count Occurrences in a Collection or Map
- Getting the Sum of Items in a Collection
- Sum the Values in a Object Array
- Represent a List as String
- Create a List with Default Values
- Add Items to a List at Specified Position
- Working with Arrays
- See if List and Object Array are Equal
- Convert Collection to Set with Only Unique Elements
- See if Sets are Equal
- Immutable Collections
- Observable Map and List
- Enhancements for Iterable Implementations
- Swapping Elements in a Collection
-
Maps
- Check if Maps are Equal
- Sorting a Map
- Turn a List into a Map
- Complex Keys in Maps
- Use inject Method on a Map
- Intersect Maps
- Subtracting Map Entries
- Process Map Entries in Reverse
- Getting a Submap from a Map
- Grouping Map Elements
- Get Value from Map or a Default Value
- Map with Default Values
- Determine Min and Max Entries in a Map
- Represent Map As String
- Turn A Map Or List As String To Map Or List
-
Closures
- Passing Closures to Methods
- Closure Arguments
- Add Some Curry for Taste
- New Ways to Curry
- Implicit Closure Coercion
- Return Closure From Another Closure or Method
- Chain Closures Together with Closure Composition
- Recursion with Closure Trampoline Capability
- Cache Closure Results with Memoization
- Info About Closure Parameters
- Setting a Closure’s Delegate
- Invoke Anonymous Closure
- Implicit Method doCall in Closure
- Closure as a Class
- Use Closures as Java Lambda Expressions
- Use Constructor as Method Pointer
-
SQL
- Groovy SQL
- Groovy SQL DataSet
- Using Named (Ordinal) Parameters with Groovy SQL
- Access ResultSetMetaData with Groovy SQL
- Paging Support in Groovy SQL
-
Files, Readers, Writers and URLs
- Working with Files
- Working on Files or Directories (or Both) with FileType
- Finding Files with FileNameFinder
- Delete Non-empty Directory Recursively with File
- Traversing a Directory
- Creating Files And Directories With Nice DSL Using FileTreeBuilder
- Calculating Directory Size
- Extra Methods for NIO Path
- withReader and withWriter
- Transforming Reader Input to Writer Output
- Append Values to Appendable Objects
- Apply Read and Write Locking
- Reading URL Content
- Use Connection Parameters to Get Text From URL
-
XML and JSON
- Pretty Print XML
- Creating XML with MarkupBuilder
- Refactor XML Creation with StreamingMarkupBuilder
- Reading XML
- Type Conversion Using GPathResult When Reading XML
- Change XML Structure
- Getting Groovy with DOM
- Nested Templates with MarkupTemplateEngine
- Use Custom Template Class with MarkupTemplateEngine
- Using Layouts with MarkupTemplateEngine
- Parse JSON with JsonSlurper
- Relax… Groovy Will Parse Your Wicked JSON
- Build JSON with JsonBuilder and Pretty Print JSON Text
- Streaming JSON with StreamingJsonBuilder
-
AST transformations
- Newify to Create New Instances
- Create a Singleton Class
- Inject Logging Using Annotations
- Customise Log AST Annotations
- Easy toString Creation for Our Classes
- Customize ToString Creation
- Tuple Constructor Creation
- Generate equals and hashcode Methods with EqualsAndHashCode Annotation
- Inherit Constructors From Parent Classes
- Canonical Annotation to Create Mutable Class
- Make Class Cloneable With @AutoClone
- Combining Annotations with AnnotationCollector
- Change Scope Script Variable with Field Annotation
- Add Java-style Listener Support with ListenerList Annotation
- Lazy Initialization of Properties
- Making a Class Immutable
- Create CopyWith Method with Immutable Annotation
- Synchronized Annotation for Synchronizing Methods
- Create Indexed Property Getter and Setter Methods
- Bound and Constrained Properties in GroovyBeans
- Delegate to Simplify Code
- Choose Which Delegated Methods to Use
- Cache Methods Invocations with Memoize Annotation
- Using Package Scoped Methods, Fields and Classes
- Use Builder AST Transformation for Fluent API
- Using Builder to Create Fluent API for Other Classes
- @Builder Definition with Extra Type Checks
- More Efficient Tail Recursion With TailRecursive Annotation
- Use Sortable Annotation to Make Classes Comparable
-
Metaprogramming
- Use Categories to Add Functionality to Classes
- Use a Category and Get a Return Value
- Mixin Functionality to Classes
- Apply Mixin to Object Instances
- Add Methods Dynamically to Classes with ExpandoMetaClass
- Create Dynamic Methods
- A Bit of metaClass DSL
- Adding or Overriding Methods with ExpandoMetaClass
- Override getProperty Method with Dynamic Groovy
- Implementing MetaClass Methods with Same Name but Different Arguments
- Add Static Methods with MetaClass to Classes
- Override and Use Old Implementation with Dynamic Methods
- Add Methods to Interfaces with ExpandoMetaClass
- Expando as Dynamic Bean
- Check If Method or Property is Available
- Intercept Methods with Interceptors
- Magic Package to Add Custom MetaClass
- Adding Extra Methods Using Extension Modules
-
DSL and Builder Support
- Building Object Graphs
- Create Simple Builders with Closures
- Solve Naming Conflicts with Builders
- Building a GUI with SwingBuilder
- Command Chain Expressions for Fluid DSLs
- Store Closures in Script Binding
- Add Imports Transparently to Scripts with ImportCustomizer
- Add AST Transformations Transparently to Scripts
- Create Our Own Script Class
- Set Script Class with BaseScript Annotation
- BaseScript with Abstract Run Script Method
- Set Delegating Class for Script
- @DelegatesTo For Type Checking DSL
- Define Compilation Customizers With Builder Syntax
- Restricting Script Syntax With SecureASTCustomizer
-
Scripts
- Using Groovy on the Command-Line
- Default Groovy Script File Extensions
- Variable Scope in Scripts
- Grab That Dependency
- See More Info About Downloading With Grape
- Configuring Grape to Use Classloader
- Use GrabResolver for Custom Repositories
- Resolve Module Location with Grape
- Change Directory For Saving Dependencies Grape
- Exclude Transitive Dependencies With Grape
- Running Groovy Scripts in Java with GroovyClassLoader
- Simple Evaluation of Groovy Expressions in Java
- Compiled Groovy Script is a Java Class
- ServerSocket Scripts
- Run Remote Scripts via URL
- Running Scripts from a JAR Archive
- Customize Groovy Console Visual Output
- Using Groovy for Git Hooks
-
Testing
- Running a Unit Test
- Testing for Expected Exceptions
- Create Stubs for Testing
-
IDE
- IntelliJ IDEA Intentions For String Values
- Turn Map Into Class With IntelliJ IDEA
- Turn Method Parameters Into Named Map Arguments With IntelliJ IDEA
- IntelliJ IDEA Formatting Of Closure Chains
-
Miscellaneous
- Inspect Method Returns Nicely Formatted Object Values
- Using Tuples
- Parsing Commandline Arguments with CliBuilder
- Get Properties from ReleaseInfo
- Using ConfigSlurper with Configuration Scripts
- Extend ConfigSlurper with Custom Environments Sections
- Check Configuration Property Is Set In ConfigObject
- Using the Template Engines
- Groovlets as Lightweight Servlets
- Access XML-RPC API
- Customise Groovydoc Output With Gradle
- Customising The Groovy Compiler
- Using the ServletCategory
- Using GroovyMBeans for Easy JMX
- Share Data in Concurrent Environment with Dataflow Variables
Authors have earned$9,675,609writing, publishing and selling on Leanpub, earning 80% royalties while saving up to 25 million pounds of CO2 and up to 46,000 trees.
Learn more about writing on Leanpub
The Leanpub 45-day 100% Happiness Guarantee
Within 45 days of purchase you can get a 100% refund on any Leanpub purchase, in two clicks.
See full terms
Free Updates. DRM Free.
If you buy a Leanpub book, you get free updates for as long as the author updates the book! Many authors use Leanpub to publish their books in-progress, while they are writing them. All readers get free updates, regardless of when they bought the book or how much they paid (including free).
Most Leanpub books are available in PDF (for computers), EPUB (for phones and tablets) and MOBI (for Kindle). The formats that a book includes are shown at the top right corner of this page.
Finally, Leanpub books don't have any DRM copy-protection nonsense, so you can easily read them on any supported device.
Learn more about Leanpub's ebook formats and where to read them
Top Books
- #1
El Manual del Manager
Keyvan Akbary, Félix López, and Álvaro Salazar¿Has deseado alguna vez el haber tenido una buena introducción al rol del Engineering Manager? En este libro aprenderás lo necesario para ejercer el rol de una manera efectiva: Expectativas y Responsabilidades del Rol, 1-1s, Ayudar a Crecer, Objetivos, Planes de Carrera, Cultura, Feedback, Contratación, Cultura de Producto y mucho más.
- #2
Functional Design and Architecture
Alexander GraninSoftware Design in Functional Programming, Design Patterns and Practices, Methodologies and Application Architectures. How to build real software in Haskell with less efforts and low risks. The first complete source of knowledge.
- #3
Ansible for Kubernetes
Jeff GeerlingAnsible is a powerful infrastructure automation tool. Kubernetes is a powerful application deployment platform. Learn how to use these tools to automate massively-scalable, highly-available infrastructure.
- #4
Ansible for DevOps
Jeff GeerlingAnsible is a simple, but powerful, server and configuration management tool. Learn to use Ansible effectively, whether you manage one server—or thousands.
- #5
Practical FP in Scala: A hands-on approach
Gabriel VolpeA practical book aimed for those familiar with functional programming in Scala who are yet not confident about architecting an application from scratch.
Together, we will develop a purely functional application using the best libraries in the Cats ecosystem, while learning about design patterns and best practices.
- #6
Tame your Work Flow
Steve Tendon and Daniel DoironDo you need a high performance enterprise governance approach improving management, execution and delivery while dealing with multiple projects/products, events, stakeholders and teams? Giving you better bottom line results, faster time to market, less work, better predictability, happier employees, and delighted clients? Then learn about TameFlow!
- #7
C++ Best Practices
Jason TurnerLevel up your C++, get the tools working for you, eliminate common problems, and move on to more exciting things!
- #8
Cloud Strategy
Gregor Hohpe“Strategy is the difference between making a wish and making it come true.” A successful migration to the cloud shouldn’t be driven by wishes, but guided by a sound strategy, frameworks, and decision models. This book tells you how—without becoming superficial nor getting lost in technology and product details.
- #9
Machine Learning Engineering
Andriy Burkov"If you intend to use machine learning to solve business problems at scale, I'm delighted you got your hands on this book."
—Cassie Kozyrkov, Chief Decision Scientist at Google
"Foundational work about the reality of building machine learning models in production."
—Karolis Urbonas, Head of Machine Learning and Science at Amazon
- #10
Composing Software
Eric ElliottAll software design is composition: the act of breaking complex problems down into smaller problems and composing those solutions. Most developers have a limited understanding of compositional techniques. It's time for that to change.
Top Bundles
- #1
Quality Software
11 Books
The Quality Software Bundle is for managers, would-be managers, and any of us who find themselves being managed and confused. This comprehensive bundle covers the entire span of software development approaches, from hacking through waterfall, cascade, prototyping, Iterative enhancement, reusable code, off-the-shelf, to Agile teams. The bundle... - #2
The Node.js Bundle
3 Books
This bundle combines three bestselling Leanpub Node.js books into a package that gives you everything you need to get started with developing Node.js applications at an unbeatable price. - #3
The Tester's Library
8 Books
The Tester's Library consists of eight five-star books that every software tester should read and re-read. As bound books, this collection would cost over $200. Even as e-books, their price would exceed $80, but in this bundle, their cost is only $49.99. Here are the books, and why they should be in your library: Perfect Software and Other... - #4
agile
11 Books
In this bundle, you will find 10 different agile books. They are about different aspects of being agile. - finding a job - doing coding dojo's - Retrospectives - Personal kanban - a non-typical coaching book and even a book that gives you an insight in the lives of some agile people. - #5
WTFlop 6M + HU - Beta Bundle
6 Books
- #6
Marionette.js A to Z
3 Books
Marionette.js has become a popular Backbone-based javascript library, because it helps you avoid boiler-plate code and focus on what makes your app special. But how do you get started?Whether you want to finally get started with dynamic client-side programming (like one reader did), or are an experienced front-end dev who has inherited a... - #7
Complete Scala Bundle
3 Books
Scala is a general-purpose programming language and it's getting extremely popular these days. Some say that learning Scala could be a challenging task. My experience, however, suggests that this is actually a myth that has very little to do with reality. With the right approach, learning Scala can be easy, fun and rewarding.The first book from... - #8
Build A Better Backbone App
3 Books
The best way to learn new development skills is through experience, but that takes time you don't have.Get the best of both worlds with this bundle: you'll learn how to produce modern web applications by learning from experienced developers like Derick Bailey and David Sulc. BackboneJS is one of the favorite tools on the web today, but it... - #9
People Skills—Soft but Difficult
7 Books
Perhaps you've been told that "lack of people skills" has been holding you back. No wonder: you may have had hundreds of hours of technical training, but little or no "people skills" guidance.You've heard it said that people skills are "soft," whereas technical skills are "hard." For you, though, technical skills are "easy," but people skills... - #10
SurviveJS - Webpack + React
2 Books
Get both SurviveJS - Webpack and SurviveJS - React for a single price!
