Java for dummies

Open and find:

• Tips on choosing an IDE for Java

• How to change primitive

types into objects

• Advice on formatting variable

content

• Different types of operators

• What to do with conditional

statements

• Directions for setting up loops

• How to create and use classes

• Secrets of manipulating strings

John Paul Mueller is a veteran technical editor and an expert on computer

industry certifications. He has written books on C#, Java, Windows programming,

and VBA, and is coauthor of the bestselling C++ All-in-One For Dummies.

$39.99 USA / $47.99 CAN / £27.99 UK

Programming Languages / Java Learn this platform-independent

language and create programs that

will run anywhere

Java is the primary language used for Android development

and many web applications, so once you master it, you can

create apps for all sorts of uses. With this eLearning Kit, you learn

Java at your own pace using written, visual, and interactive

lessons. Discover how to obtain and install Java and go from

beginner to programmer extraordinaire!

• Install the newest version — find and install the most up-to-date

Java version for Windows®, Mac®, or Linux®

• Explore variables — learn to use primitive variables to store

information and object variables to perform tasks within your

application

• Get in the loop — repeat tasks with loops, create and use classes,

access data sets, and work with strings

• Banish bugs — detect and solve problems to prevent application

crashes

• XML makes it better — add value to your applications by working

with XML data

Includes

Online Course

See inside for details!

Includes:

• Full color book plus

online training course

• FREE 1 year access to

online self-paced training

via access code

• 10 interactive lessons cover

the essentials of Java

John Paul Mueller

eLEARNING KIT

KIT

LEARNING

Java®

Java®

Cover Images: Front Cover Image ©iStockphoto.com/

olaser; Back and Inside Cover Images Courtesy of

John Paul Mueller

Java®

LEARNING KIT

by John Paul Mueller

Java®

LEARNING KIT

Java® eLearning Kit For Dummies®

Published by

John Wiley & Sons, Inc.

111 River Street

Hoboken, NJ 07030-5774

www.wiley.com

Copyright © 2014 by John Wiley & Sons, Inc., Hoboken, New Jersey

Published by John Wiley & Sons, Inc., Hoboken, New Jersey

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Manufactured in the United States of America

10 9 8 7 6 5 4 3 2 1

Contents at a Glance

Introduction ................................................................ 1

Chapter 1: Starting With Java...........................................................................................7

Chapter 2: Using Primitive Variables ............................................................................47

Chapter 3: Using Object Variables.................................................................................75

Chapter 4: Formatting Variable Content.....................................................................111

Chapter 5: Working with Operators ............................................................................129

Chapter 6: Working with Conditional Statements .....................................................165

Chapter 7: Repeating Tasks Using Loops ...................................................................185

Chapter 8: Handling Errors...........................................................................................209

Chapter 9: Creating and Using Classes .......................................................................247

Chapter 10: Accessing Data Sets Using Arrays and Collections ..............................285

Chapter 11: Performing Advanced String Manipulation...........................................337

Chapter 12: Interacting with Files................................................................................359

Chapter 13: Manipulating XML Data............................................................................387

Index ...................................................................... 403

Table of Contents

Introduction ................................................................. 1

About This Kit..................................................................................................1

How This Book Is Organized..........................................................................2

Conventions Used in This Book.....................................................................4

Foolish Assumptions.......................................................................................5

Icons Used in This Kit .....................................................................................5

Accessing the Java eCourse ...........................................................................6

Class Is In..........................................................................................................6

Chapter 1: Starting With Java . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Considering Why You’d Use Java................................................................10

Using a popular language....................................................................10

Working with a standardized language.............................................11

Creating applications for multiple platforms...................................12

Defining other reasons to use Java....................................................12

Obtaining and Installing the Java 8 JDK......................................................13

Downloading Java 8 .............................................................................13

Performing the Windows installation................................................14

Performing the Linux installation ......................................................15

Performing the Mac installation.........................................................16

Accessing the Java executables.........................................................16

Choosing an IDE for Java ..............................................................................21

Working with a text editor..................................................................21

Finding an IDE.......................................................................................22

Determining when to use a particular development

environment......................................................................................23

Creating a Simple Application......................................................................24

Writing the application code..............................................................24

Identifying the parts of the application ............................................26

Compiling the Simple Application...............................................................27

Opening the command prompt..........................................................28

Creating the compiled .class file........................................................29

Executing the Simple Application................................................................30

Using the Java command ....................................................................30

Understanding the JavaW command difference..............................31

Adding Comments to Your Java Code ........................................................32

Grasping the importance of comments ............................................32

Creating single-line comments...........................................................33

Creating multiline comments .............................................................34

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Java eLearning Kit For Dummies

Importing Other Classes...............................................................................34

Introducing the Java API.....................................................................35

Importing single classes......................................................................36

Importing an entire package...............................................................37

Obtaining Help for Java ................................................................................39

Getting local help.................................................................................40

Getting local utility help......................................................................41

Locating Java information online.......................................................42

Summing Up ...................................................................................................42

Try-it-yourself lab ................................................................................44

Know this tech talk..............................................................................44

Chapter 2: Using Primitive Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Working with the Primitive Types...............................................................50

byte........................................................................................................51

short ......................................................................................................55

int...........................................................................................................57

long ........................................................................................................59

float........................................................................................................61

double....................................................................................................63

boolean..................................................................................................65

char........................................................................................................67

Creating and Using Constants......................................................................69

Summing Up ...................................................................................................71

Try-it-yourself lab ................................................................................72

Know this tech talk..............................................................................72

Chapter 3: Using Object Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

Working with Common Objects...................................................................78

String .....................................................................................................78

Calendar ................................................................................................80

BigDecimal............................................................................................81

BigInteger..............................................................................................84

Changing Primitive Types into Objects ......................................................86

Automatic boxing and unboxing........................................................87

Byte versus byte ..................................................................................87

Short versus short...............................................................................90

Integer versus int.................................................................................92

Long versus long..................................................................................94

Float versus float..................................................................................97

Double versus double .......................................................................100

Boolean versus boolean....................................................................101

Character versus char.......................................................................101

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Table of Contents

Using the New Date and Time API.............................................................103

Viewing the date and time API .........................................................103

Creating and using dates and times ................................................105

Working with Enumerations.......................................................................106

Summing Up .................................................................................................108

Try-it-yourself lab ..............................................................................109

Know this tech talk............................................................................110

Chapter 4: Formatting Variable Content . . . . . . . . . . . . . . . . . . . . . . . . 111

Displaying Percentages...............................................................................113

Using Escape Sequences.............................................................................115

Displaying Date and Time...........................................................................118

Using the Calendar object.................................................................118

Using the date and time API .............................................................121

Displaying Currency Values .......................................................................124

Summing Up .................................................................................................126

Try-it-yourself lab ..............................................................................126

Know this tech talk............................................................................127

Chapter 5: Working with Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

Storing Data Using Assignment Operators...............................................132

Performing a simple assignment......................................................132

Performing a combined assignment................................................134

Performing Math Tasks with Arithmetic Operators ...............................137

Performing simple math tasks .........................................................137

Executing complex math tasks.........................................................140

Modifying Variable Content Using Unary Operators ..............................143

Incrementing and decrementing numbers .....................................144

Understanding negation, bitwise Not, and Boolean Not...............145

Creating objects .................................................................................148

Casting one type to another .............................................................148

Using Relational and Conditional Operators ...........................................151

Checking value equality....................................................................152

Performing a type comparison.........................................................154

Performing a conditional evaluation...............................................156

Understanding Operator Precedence .......................................................157

Summing Up .................................................................................................161

Try-it-yourself lab ..............................................................................162

Know this tech talk............................................................................163

Chapter 6: Working with Conditional Statements . . . . . . . . . . . . . . . 165

Using a Simple If Statement........................................................................167

Performing One of Two Tasks with If. . .Else............................................169

Nesting If Statements ..................................................................................171

Selecting from Multiple Conditions Using Switch ...................................174

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Java eLearning Kit For Dummies

Executing a Default Task ............................................................................177

Displaying Boolean Values .........................................................................180

Summing Up .................................................................................................182

Try-it-yourself lab ..............................................................................182

Know this tech talk............................................................................183

Chapter 7: Repeating Tasks Using Loops . . . . . . . . . . . . . . . . . . . . . . . 185

Performing Tasks a Set Number of Times ................................................187

Using the standard for loop..............................................................187

Using the break statement................................................................189

Using the continue statement ..........................................................191

Nesting for loops................................................................................193

Executing Tasks Until Complete................................................................196

Using the while loop..........................................................................197

Checking after the first execution with the do . . .while loop ......199

Interacting with Objects .............................................................................201

Creating a basic for-each loop..........................................................202

Using the for-each loop with enumerations ...................................203

Summing Up .................................................................................................206

Try-it-yourself lab ..............................................................................206

Know this tech talk............................................................................207

Chapter 8: Handling Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

Understanding Error Sources ....................................................................212

Classifying when errors occur .........................................................212

Distinguishing error types................................................................215

Catching Errors............................................................................................222

Optional error handling ....................................................................222

Handling more-specific to less-specific errors...............................225

Using Optional objects to avoid exceptions...................................229

Throwing Errors ..........................................................................................234

Throwing errors during exceptional conditions............................234

Passing errors to the caller ..............................................................237

Required error handling ...................................................................238

Summing Up .................................................................................................243

Try-it-yourself lab ..............................................................................244

Know this tech talk............................................................................245

Chapter 9: Creating and Using Classes . . . . . . . . . . . . . . . . . . . . . . . . 247

Understanding the Structure of Classes...................................................250

Calling methods .................................................................................250

Allocating properties.........................................................................252

Considering inheritance....................................................................253

xi

Table of Contents

Defining Variable Scope..............................................................................257

Considering default scope ................................................................257

Observing scope within a block.......................................................265

Defining a Class with Event Support.........................................................266

Defining an event ...............................................................................266

Creating an event listener interface ................................................268

Implementing the event as part of a class definition ....................269

Demonstrating use of the event in a class......................................272

Using the Class with Events .......................................................................275

Working with Anonymous Inner Classes..................................................277

Working with Lambda Expressions...........................................................279

Summing Up .................................................................................................281

Try-it-yourself lab ..............................................................................282

Know this tech talk............................................................................283

Chapter 10: Accessing Data Sets Using Arrays and Collections . . 285

Performing Basic Array Tasks ...................................................................288

Defining an array................................................................................288

Initializing an array............................................................................289

Using the for-each loop with arrays ................................................289

Determining the array characteristics............................................291

Changing the array size.....................................................................293

Sorting array data ..............................................................................296

Creating Multidimensional Arrays ............................................................298

Defining a two-dimensional array ....................................................298

Obtaining the number of dimensions in an array..........................300

Developing variable-length arrays of arrays ..................................304

Interacting with Array-Like Structures .....................................................310

Using stacks........................................................................................310

Working with queues.........................................................................314

Employing deques .............................................................................318

Iterating arrays by using List elements and

lambda expressions .......................................................................322

Using Maps to Create Collections .............................................................323

Defining the map................................................................................324

Creating a map example....................................................................325

Working with Java Annotations.................................................................328

Understanding annotations..............................................................328

Using annotations ..............................................................................331

Summing Up .................................................................................................332

Try-it-yourself lab ..............................................................................333

Know this tech talk............................................................................334

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Java eLearning Kit For Dummies

Chapter 11: Performing Advanced String Manipulation . . . . . . . . . . 337

Converting Data to and from Strings ........................................................340

Finding Information in Strings ...................................................................344

Looking at the beginning or end of the string................................344

Working with substrings...................................................................346

Modifying String Content............................................................................348

Extracting characters........................................................................348

Splitting strings ..................................................................................351

Formatting String Output ...........................................................................352

Summing Up .................................................................................................357

Try-it-yourself lab ..............................................................................357

Know this tech talk............................................................................358

Chapter 12: Interacting with Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359

Interacting with the File System ................................................................361

Managing directory information......................................................363

Interacting with files..........................................................................365

Defining file and directory attributes ..............................................368

Manipulating path data .....................................................................371

Opening Files for Reading...........................................................................373

Writing to Files.............................................................................................376

Creating and Using Temporary Files.........................................................379

Summing Up .................................................................................................385

Try-it-yourself lab ..............................................................................385

Know this tech talk............................................................................386

Chapter 13: Manipulating XML Data . . . . . . . . . . . . . . . . . . . . . . . . . . . 387

Understanding How XML and Java Interact.............................................389

Reading XML Data from Files .....................................................................390

Writing XML Data to Disk ...........................................................................396

Summing Up .................................................................................................400

Try-it-yourself lab ..............................................................................401

Know this tech talk............................................................................401

Index ....................................................................... 403

Introduction

I

f you’ve been thinking about taking a class online (it’s all the rage

these days), but you’re concerned about getting lost in the electronic

fray, worry no longer. Java eLearning Kit For Dummies is here to help

you, providing you with an integrated learning experience that includes

not only the book you hold in your hands but also an online version of the

course at http://learn.dummies.com. Consider this introduction

your primer.

About This Kit

Each piece of this eLearning Kit works in conjunction with the others,

although you don’t need them all to gain valuable understanding of the key

concepts covered here. Whether you follow along with the book, go online

to see the course, or some combination of the two, Java eLearning Kit For

Dummies teaches you how to:

✓ Install a copy of Java on your particular platform. (Windows, Linux, and

Macintosh instructions are all provided.)

✓ Obtain an Integrated Development Environment (IDE) for your copy of

Java, should you wish to use one.

✓ Write a basic Java program.

✓ Obtain help using Java to write applications for your machine.

✓ Use variables to store information for use in your application.

✓ Create and use objects that model real-world information.

✓ Employ the new date and time API for Java in your applications.

✓ Perform mathematical tasks using Java.

✓ Make decisions based on input that the application receives.

✓ Perform repetitive tasks.