The Groovy 2 Tutorial
The Groovy 2 Tutorial
An introductory text for Groovy developers
About the Book
The Groovy 2 Tutorial takes you through the essential aspects of the Groovy programming language. You'll learn about the general syntax and pick up helpful tips. Importantly, you'll see where Groovy can make programming more about solving problems and less about tedious syntax.
Groovy is a great programming language for those who enjoy programming (or are new to it!) but find languages such as Java to be cumbersome. Learning Groovy will give you the ability to not only write Groovy programs but to also unlock a range of great technologies such as Grails and Gradle as well as frameworks that run on the Java Virtual Machine such as Spring.
Written in a straight-forward tone, each chapter focusses on a specfic language element and provides a range of examples for you to try out in the Groovy Console. You don't need lots of tooling - just some time and a basic PC or laptop.
License
About the Author
Table of Contents
-
-
Introduction
- Something Wrong?
- Bookmarks
- Conventions Used in This Book
- Your Rights and This Book
- Legal Notices
-
Introduction
-
I Getting started
- 1. Introduction
-
2. Installing Groovy
- Don’t Install Groovy
- Install a Java Virtual Machine
- Install Groovy
-
3. Your first lines of Groovy
- Examining the script
- 4. Running a script
- 5. Compiling Groovy
-
6. Comments
- Single-line comments
- Multi-line comments
- Usage to avoid
- Groovydoc
-
7. Statements
- Usage to avoid
-
8. The
assertstatement- Handling failed assertions
- 9. Reserved Words
-
10. Packages
-
Using
import - Built in Libraries
- Useful third-party libraries
-
Using
- 11. Grape
-
II Variables
- 12. Introduction
-
13. Declaring Variables
- Variable names
- Data Types
-
14. Objects
- Declaring and using a class
- Useful Methods
- Existing classes
- Classes and literal values
-
15. Booleans
- Useful Methods
-
16. Numbers
- Integers
- Decimals
- Scientific notation
- Number Systems
- Useful Methods and Properties
-
17. Strings
- Escape sequences
- GStrings
- Multiline Strings
- Building Strings
- Useful Methods
-
18. Collections
- Lists
- Maps
-
19. Arrays
- Manipulating arrays
-
20. Ranges
- Half-Open Ranges
- Ranges of Objects
- Ranges and List Indexes
- Ranges and Loops
- Useful Methods
-
21. Regular Expressions
- Regular Expression Syntax
- Useful Methods
-
22. Data types
- Groovy’s use of types
- Using a specific type
-
The
nullValue - Available data types
- Type Conversions
-
III Operators
-
23. Introduction
- Arithmetic and Conditional Operators
- String Operators
- Regular Expression Operators
- Collection Operators
- Object Operators
- 24. Operator Overloading
-
25. Numeric Operators
- Operator Precedence
- Order of Precedence
- 26. Simple Assignment Operator
- 27. The Complement Operator
-
28. Equality Operators
- What Is Equality?
- Precedence
- Overloading Equality
-
29. Arithmetic operators
- Additive Operators
- Multiplicative Operators
- The Power operator
- Precedence
-
30. Relational Operators
- Spaceship
- Overloading the relational operators
-
31. Increment and Decrement Operators
- Overloading the Increment and Decrement Operators
-
32. Conditional Operators
- What Is Truth?
- Evaluation
- Conditional-And
- Conditional-Or
- Conditional Operator
-
33. Bitwise Operators
- Truth Tables
- Flag example
- Shift Example
- 34. Compound Assignment Operators
-
35. String Operators
- Concatenate Operator
- Append Operator
- Remove Operator
- Remove In-Place Operator
- Repeat Operator
- Repeat In-PlaceOperator
- Increment and Decrement Operators
- Warning: Strings Are Expensive!
- Templates
-
36. Regular Expression Operators
-
Find (
=~) -
Match (
==~)
-
Find (
-
37. Collection operators
- Membership Operator (Lists and Maps)
- Append (Lists and Maps)
- Addition (Lists and Maps)
- Subtraction (Lists and Maps)
- Compound Assignment Operators (Lists and Maps)
- Spread Operator (Lists)
- Spread-Dot Operator (Lists)
- A Little Set Theory
-
38. Object Operators
- Safe Navigation Operator
- Casting Operator
- Identity Operator
- Type Comparison
- Field Operator and Method Reference
-
23. Introduction
-
IV Control Flow Statements
- 39. Introduction
-
40. Blocks
- Variable Scope
-
41. The
ifStatement-
if-else -
if-else if-else
-
-
42. The
switchStatement-
The Versatile Groovy
switch - Using Ranges
- Using Regular Expressions
- Using Class Checks
-
The Versatile Groovy
-
43. The
forLoop-
The
for-inLoop - The Java for-each
-
A C-style
forLoop
-
The
-
44. The
whileloop-
There is no
do...whileloop
-
There is no
-
45. Branching statements
- break
- continue
- Labelled branching
- return
-
V Exceptions
- 46. Introduction
-
47. Common Exceptions
- java.lang.NullPointerException
- java.lang.AssertionError
- java.lang.NumberFormatException
- groovy.lang.MissingPropertyException
- groovy.lang.MissingMethodException
- java.lang.IndexOutOfBoundsException
- java.lang.ArrayIndexOutOfBoundsException
- 48. Anatomy of an Exception
-
49. Try-Catch-Finally
- Scope
- try-catch
- try-catch-finally
- try-finally
- 50. How Much Should We try?
-
51. Causing an Exception
- Constructing an Exception
- Creating Your Own Exception
- 52. Catching Errors
- 53. Methods and Exceptions
-
VI Methods
- 54. Introduction
- 55. The Basics
-
56. Parameters
- Declaring data types for parameters
- Multiple parameters
- 57. Default Values for Parameters
- 58. Named Arguments
- 59. Variable Arguments (Varargs)
-
60. Return value
- Multiple Returns
- Declaring data types for return values
- Sequential method calls
- 61. Throwing an exception
- 62. Documenting a method
-
63. Techniques
- Valid parameters
- Comment your method
- Check the parameters
- Get really typed
- Testing
-
VII Closures
- 64. Introduction
-
65. Introducing Closures
- Anonymous Functions
- The ‘it’ parameter
- 66. Parameters
- 67. Returning Values
-
68. Closures as Method Parameters
- Methods with Closure Parameters
-
69. Loops and closures
-
each -
collect -
sort
-
-
70. Useful Methods That Use Closures
-
any -
findandfindAll -
split -
with
-
-
71. Closure scope
- A More Involved Example
-
VIII Object-oriented programming
- 72. Introduction
-
73. Expando
- Using Expando with CSV data
-
74. The basics of OO
- Classes
- Interfaces
- Inheritance
- Traits
- Packages
- Summary
-
75. Properties and Fields
- Properties
- Fields
- Default values
- Casting maps to objects
-
76. Getters and Setters
- Fields
- Pseudo properties
-
77. Methods
- Overloading
-
78. Constructors
- Writing your own constructor(s)
- TupleConstructor annotation
- Instance initializer blocks
- When and How Things Happen
- Constructors and instance methods
-
79. Class Methods and Variables
- Static initializer blocks
-
80. Final Variables
- Final fields and the map-like constructor
- Final objects
- Final classes and methods
-
81. Access Modifiers
- Applying Access Modifiers
-
82. Useful Annotations
- ToString
- EqualsAndHashCode
- Canonical
- Immutable
- 83. Let Go of That Instance!
- 84. Enums
-
85. The
synchronizedmodifier
-
IX More object-oriented programming
-
86. Introduction
- The Shapes demo
-
87. Organising your code
- Packages
- Compiling and running
- 88. Naming your packages
- 89. Packages and directory structure
- 90. The Shapes demo - packages
- 91. Interfaces
- 92. Referring to objects by their interface
-
93. General advice for interfaces
- Groovy interfaces don’t allow default methods
- The constant interface antipattern
- 94. The Shapes demo - Interfaces
- 95. Traits
- 96. Trait properties and fields
- 97. Trait methods
- 98. Trait static members
-
99. The class-trait relationship
- Self types
- 100. Traits and interfaces
- 101. Implementing multiple traits
- 102. The Shapes demo - Traits
-
103. Inheritance
- Some inheritance theory
-
104. Subclassing
- Type comparison
- 105. Final Classes and Methods
- 106. Abstract classes
- 107. The Shapes demo - Inheritance
-
86. Introduction
-
X Going further
-
108. Other Topics
- Type Checking
- Static Compilation
- Metaprogramming
- Generics
- Inner Classes
- Single abstract methods
-
109. The great beyond
- Build large applications
- Use the Groovy ecosystem
-
Appendix: The Shapes demo code listing
-
package org.groovy_tutorial.shapes -
package org.groovy_tutorial.shapes.triangle -
package org.groovy_tutorial.shapes.triangle
-
- Colophon
-
108. Other Topics
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