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Appendix A: Java/Groovy ¹

Feature	Java	Groovy
Public class	public class	class
Loops	for(Type it : c){...}	c.each {...}
Lists	List list = Arrays.asList(1,2,3);	def list = [1,2,3]
Maps	Map m = ...; m.put(x,y);	def m = [x: y]
Function def.	void method(Type t) {}	def method(t) {}
Mutable value	Type t	def t
Immutable value	final Type t	final t
Null safety	(x == null ? null : x.y)	x?.y
Null replacement	(x == null ? "y" : x)	x ?: "y"
Sort	Collections.sort(list)	list.sort()
Wildcard import	import java.util.*;	import java.util.*
Var-args	(String... args)	(String... args)
Type parameters	Class<T>	Class<T>
Equals	a.equals(b)	a == b

No Java Analog

Feature	Groovy
Default closure arg.	it
Default value	def method(t = "yes")
Add method to object	t.metaClass.method = {}
Auto-delegate	@Delegate
Extension methods	Categories
Rename import	import java.util.Vector as Vec
Range	def range = [a..z]
Slice	def slice = list[0..3]
<< Operator (leftShift)	list << addMeToList
Cast operation	def dog = [name: "Fido", speak: {println "woof"}] as Dog
GString	def gString = "Dog's name is ${dog.name}"

Appendix B: Java/Scala ²

Feature	Java	Scala
Public class	public class	class
Loops	for(Type it : c){...}	c.foreach {...}
Lists	List list = asList(1,2,3);	val list = List(1,2,3)
Maps	Map m = ...; m.put(x,y);	val m = Map(x -> y)
Function def.	void method(Type t) {}	def method(t: Type) = {}
Mutable value	Type t	var t: Type
Immutable value	final Type t	val t: Type
Null safety	(x == null ? null : x.y)	for (a <- Option(x)) yield a.y
Null replacement	(x == null ? "y" : x)	Option(x) getOrElse "y"
Sort	Collections.sort(list)	list.sort(_ < _)
Wildcard import	import java.util.*;	import scala.collection._
Var-args	(String... args)	(args: String*)
Type parameters	Class<T>	Class[T]
Concurrency	Fork/Join, Parallel Streams	Akka

No Java Analog

Feature	Scala
Default closure arg.	_(underscore is positionally matched)
Default value	def method(t:String = "yes")
Add method to object	useTrait
Auto-delegate	useTrait
Extension methods	implicit class
Rename import	import scala.collection.{Vector => Vect}

Null, Nil, etc.

Type	Description
Null	ATrait with one instance, null, similar to Java’s null.
Nil	Represents an emptyList of zero length.
Nothing	ATrait that is a subtype of everything. There are no instances of it.
None	None signifies no result. Option has two subclasses:Some andNone .
Unit	Type to use on a method that does not return a value.

Appendix C: Java/JavaScript ³

Feature	Java	JavaScript
Public class	public class	function
Loops	for(Type it : c){...}	c.forEach(function(){...})
Lists	List list = asList(1,2,3);	var list = [1,2,3]
Maps	Map m = ...; m.put(x,y);	var m = {x: y}
Function def.	void method(Type t) {}	function method(t) {}
Mutable value	Type t	var t
Immutable value	final Type t	const t
Null safety	(x == null ? null : x.y)	(x == null ? null : x.y)
Null replacement	(x == null ? "y" : x)	x ? x : 'y'
Sort	Collections.sort(list)	list.sort()
Wildcard import	import java.util.*;	N/A
Var-args	(String... args)	()
Type parameters	Class<T>	N/A

No Java Analog

Feature	JavaScript
Add method to object	t.method = function() {}
Extension methods	Type.prototype.method = function() {}
Add property	t.name = “Bob”

Appendix E: Free Online Learning

Khan Academy ¹⁴ is amazing. If you haven’t seen it yet, please take a look. The founder started out by teaching his cousins remotely and putting the videos on YouTube. He then created hundreds of videos, teaching millions of people. Khan Academy encompasses nearly every subject: science, math, finance, history, computer science, and more. The amazing thing is, it’s all free!

Contrast this, for example, with the price of higher education in the United States. It’s been skyrocketing, ¹⁵ owing partly to government-funded student loans and partly to other factors.

Online education is flourishing. Many classes in this space are free or very inexpensive. Coursera ¹⁶ allows students to take courses from leading institutions, such as Stanford, Princeton, and Emory University. Online interactive platforms such as Codecademy ¹⁷ (free) offer to teach you to program.

The Death of College?

Is there any point in going to college anymore? College offers so many benefits other than the obvious textbook knowledge: learning to work with others, the social life, athletics, and accountability (not to mention the prestige associated with a degree). However, it seems like these benefits could be achieved in different, less expensive ways—perhaps not a degree but something like certificates, which could be just as useful.

You’ve probably been able to simply buy books and teach yourself or learn by doing, so let’s not overestimate the potential of online learning. However, with so many alternatives cropping up and the advantages of college being questionable, it’s easy to imagine education being less expensive in the future.

Sustainability

Sure that’s all great, but are these “schools” sustainable? What is the business model? Well, Khan Academy is a not-for-profit ¹⁸ venture, so its future is entirely dependent on the generosity of donors. The other institutions cited are conventional companies. Some offer free samplers, with normal courses requiring tuition. Coursera and its peers will most likely charge only for the certificate, not the actual learning. This is a promising business model.

More Online Resources

The following is a list of various web sites offering the opportunity to learn just about anything:

Khan Academy ¹⁹ : Math, Python
Codecademy ²⁰ : JavaScript, HTML/CSS, PHP, Python, Ruby
Coursera ²¹ : Algorithms, Programming, etc.
Pluralsight ²² : Ruby, Python, JavaScript, HTML/CSS, iOS
Udacity ²³ : Everything from “Introduction to Computer Science” to “Applied Cryptography”
CodeCombat ²⁴ : Learn JavaScript through a game
EdX ²⁵ : Free online courses by Harvard, MIT, and more

Appendix F: Java

Java ²⁶ was first developed in the 1990s by James Gosling. It borrowed much of its syntax from C and C++ to be more appealing to programmers at the time. Java was owned by Sun Microsystems, which was acquired by Oracle in 2010.

Java is astatically typed ,object-oriented language. “Statically typed” means that every variable and parameter must have a defined type, as opposed to languages such as JavaScript, which are dynamically typed. “Object-oriented” (OO) means that data and functions are grouped into objects (functions are usually referred to asmethods in OO languages). With the introduction of lambda expressions in Java 8, the Java language better supports the functional style of programming as well.

Java code is compiled to bytecode that runs on a virtual machine (the Java Virtual Machine, JVM ). The virtual machine handles garbage collection and allows Java to be compiled once and run on any OS or hardware that has a JVM. This is an advantage over C/C++, which must be compiled directly to machine code and has no automatic garbage collection (the programmer has to allocate and de-allocate memory).

The standard implementation of the JVM is packaged in two different ways: the JRE (Java Runtime Environment) and the JDK (Java Development Kit) . The JRE is strictly for running Java as an end user, while the JDK is for developing Java code. The JDK comes with thejavac command for compiling Java code to bytecode, among other things.

As of this writing, Java is one of the most popular programming languages in use, ²⁷ particularly for server-side web applications.

The Java ecosystem is huge. It’s mainly composed of JVMs, libraries, tools, and IDEs. If you’d like to learn more, you could readModern Java: Second Edition ²⁸ which delves more deeply into the ecosystem.

Afterword

If you’ve gotten this far, congratulations! You probably know a lot more than when you started (I hope). This book ended up being a lot longer than initially planned and, at first, some readers might even think, “Hey! That’s not easy!”

It turns out that programming can be challenging and complex. There are many layers to a typical program covering different levels of abstraction, and a whole version control mess if you work on a large team. However, I stand by the title of the book. To me, what really makes something easy is if it’s fun or rewarding. If it’s not fun or rewarding, even the simplest task, such as doing dishes, seems difficult. However, if something is fun, a person will be inclined to spend hours a day at it, becoming a master through practice over time.

I hope that you have found something fun in this book. If not, please think of an alternative you do find fun or rewarding (sports, music, movies, or something else) and write a program related to it. That is the best way to learn programming.

You can also benefit from looking at open source projects. For example, go to github ²⁹ and search for existing projects in the language of your choice. There are also a lot of resources out there to help people learning how to program. Some are listed in the appendix of this book.

Index

Actor design pattern

Application program interface (API)

Arrays

assertEquals method

Assignment

@Autowired

Behavior-driven development (BDD)

Boolean algebra/Boolean logic

Cassandra

Chain of responsibility pattern

Class and object

comments

create new object

field, properties and methods

Groovy

Javascript prototype

Scala

Conditional statement

Boolean logic

if, then, else

looping

switch

D, E

Design patterns

actors

Chain of Responsibility

DSL

closures

definition

operators

Facade

MVC

observer

Domain-specific language (DSL)

doSomething() method

Facade pattern

Functional interface

Functional programming (FP)

closure

concat

definition

filter

functions

Groovy

immutability

limit

map function

reduce

Scala

Stream<T> interface

G, H

getBytes() method

getText() method

git pull command

git push command

Gradle

definition

dependencies

gradle buildApp

plug-ins

project

Grails

Griffon

Groovy

Inheritance

abstract class

annotations

autoboxing

composition

definition

enums

interfaces

object

constructor

JavaScript

packages

parent class

example

JavaScript

unboxing

@Inject

Input/Output files

API

BufferedReader

download files

paths

PrintWriter

Interfaces

Interpreted languages

Interweb

Grails

applications

cloud

definition

domain (model) classes, creation

static hasMany field

plug-ins

REST

CRUD

JAX-RS API

JSON views

web framework

Web 101

J, K

Java Development Kit (JDK)

Java/Groovy

groovyConsole

installation

Java runtime environment (JRE)

Java virtual machine (JVM)

JUnit

Lists

generic type

Groovy

Javascript arrays

Scala

makeDragonNamed() method

Maps

example

Groovy

JavaScript

methods

Scala

Math

adding, subtracting

JDK

methods

random() method

Math.random() method

Maven

definition

executing code

phases

POM

project creation

Methods

def keyword

invoking

main method

parameters

returns Dragon object

static method

Varargs

Method signature

Model–view–controller (MVC)

MongoDB

@Nonnegative

@Nonnull

NoSQL (Non-relational) databases

Cassandra

MongoDB

Redis

sharding

VoltDB

Observer pattern

@Override annotation

P, Q

Primitive types

Programming

Project object model (POM)

Redis

Refactoring

definition

examples

OOP

REpresentational State Transfer (REST)

Scala

Sets

SQL (Relational) database

ACID

connections

foreign key

INTEGER

select statement

table

where clause

Statements

Static method

Swinging graphics

Buttons

fake browser

Griffon

hello window

2D/3D

Testing

JUnit

assumptions

definition

Hamcrest core matchers

Spock

BDD

definition

exceptions

lists/tables of data

mocking

simple test

specifications

TDD

types

toURL() method

@Unroll annotation

User experience (UX)

characteristics

choices

context

direction

KISS

skeuomorphism

wizard/witch and muggle

Utilities

currency

dates and time

Groovy date

Java

Java DateFormat

JavaScript date

Scanner

TimeZone

V, W, X, Y, Z

Varargs/variable arguments

Version control system (VCS)

Git

Mercurial

SVN

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