A new edition of the bestselling guide to Java
If you want to learn to speak the world’s most popular programming language like a native, Java For Dummies is your ideal companion. With a focus on reusing existing code, it quickly and easily shows you how to create basic Java objects, work with Java classes and methods, understand the value of variables, learn to control program flow with loops or decision-making statements, and so much more!
Java is everywhere, runs on almost any computer, and is the engine that drives the coolest applications. Written for anyone who’s ever wanted to tackle programming with Java but never knew quite where to begin, this bestselling guide is your ticket to success! Featuring updates on everything you’ll encounter in Java 9—and brimming with tons of step-by-step instruction—it’s the perfect resource to get you up and running with Java in a jiffy!
- Discover the latest features and tools in Java 9
- Learn to combine several smaller programs to create a bigger program
- Create basic Java objects and reuse code
- Confidently handle exceptions and events
If you’re ready to jump into Java, this bestselling guide will help keep your head above water!
Table of Contents:
Introduction 1
How to Use This Book 1
Conventions Used in This Book 2
What You Don’t Have to Read 2
Foolish Assumptions 3
How This Book Is Organized 4
Part 1: Getting Started with Java 4
Part 2: Writing Your Own Java Program 4
Part 3: Working with the Big Picture: Object-Oriented Programming 5
Part 4: Smart Java Techniques 5
Part 5: The Part of Tens 5
Icons Used in This Book 5
Beyond the Book 6
Where to Go from Here 7
Part 1: Getting Started with Java 9
Chapter 1: All about Java 11
What You Can Do with Java 12
Why You Should Use Java 13
Getting Perspective: Where Java Fits In 14
Object-Oriented Programming (OOP) 16
Object-oriented languages 16
Objects and their classes 18
What’s so good about an object-oriented language? 19
Refining your understanding of classes and objects 21
What’s Next? 23
Chapter 2: All about Software 25
Quick-Start Instructions 25
What You Install on Your Computer 28
What is a compiler? 29
What is a Java Virtual Machine? 32
Developing software 39
What is an integrated development environment? 40
Chapter 3: Using the Basic Building Blocks 43
Speaking the Java Language 43
The grammar and the common names 44
The words in a Java program 45
Checking Out Java Code for the First Time 47
Understanding a Simple Java Program 48
The Java class 49
The Java method 50
The main method in a program 52
How you finally tell the computer to do something 53
Curly braces 55
And Now, a Few Comments 59
Adding comments to your code 60
What’s Barry’s excuse? 63
Using comments to experiment with your code 63
Part 2: Writing Your Own Java Programs 65
Chapter 4: Making the Most of Variables and Their Values 67
Varying a Variable 68
Assignment statements 70
The types of values that variables may have 71
Displaying text 74
Numbers without decimal points 75
Combining declarations and initializing variables 77
Experimenting with JShell 78
What Happened to All the Cool Visual Effects? 82
The Atoms: Java’s Primitive Types 82
The char type 83
The boolean type 85
The Molecules and Compounds: Reference Types 87
An Import Declaration 91
Creating New Values by Applying Operators 93
Initialize once, assign often 97
The increment and decrement operators 98
Assignment operators 102
Chapter 5: Controlling Program Flow with Decision-Making Statements 105
Making Decisions (Java if Statements) 106
Guess the number 106
She controlled keystrokes from the keyboard 107
Creating randomness 110
The if statement 111
The double equal sign 112
Brace yourself 112
Indenting if statements in your code 113
Elseless in Ifrica 114
Using Blocks in JShell 116
Forming Conditions with Comparisons and Logical Operators 117
Comparing numbers; comparing characters 117
Comparing objects 118
Importing everything in one fell swoop 121
Java’s logical operators 121
Vive les nuls! 124
(Conditions in parentheses) 125
Building a Nest 127
Choosing among Many Alternatives (Java switch Statements) 130
Your basic switch statement 130
To break or not to break 134
Strings in a switch statement 136
Chapter 6: Controlling Program Flow with Loops 139
Repeating Instructions Over and Over Again (Java while Statements) 140
Repeating a Certain Number of Times (Java for Statements) 143
The anatomy of a for statement 145
The world premiere of “Al’s All Wet” 147
Repeating until You Get What You Want (Java do Statements) 150
Reading a single character 154
File handling in Java 154
Variable declarations and blocks 156
Part 3: Working with the Big Picture: Object-Oriented Programming 159
Chapter 7: Thinking in Terms of Classes and Objects 161
Defining a Class (What It Means to Be an Account) 162
Declaring variables and creating objects 164
Initializing a variable 167
Using an object’s fields 167
One program; several classes 168
Public classes 168
Defining a Method within a Class (Displaying an Account) 169
An account that displays itself 171
The display method’s header 172
Sending Values to and from Methods (Calculating Interest) 173
Passing a value to a method 176
Returning a value from the getInterest method 178
Making Numbers Look Good 180
Hiding Details with Accessor Methods 185
Good programming 185
Public lives and private dreams: Making a field inaccessible 188
Enforcing rules with accessor methods 190
Barry’s Own GUI Class 190
Chapter 8: Saving Time and Money: Reusing Existing Code 197
Defining a Class (What It Means to Be an Employee) 198
The last word on employees 198
Putting your class to good use 200
Cutting a check 204
Working with Disk Files (a Brief Detour) 205
Storing data in a file 205
Copying and pasting code 206
Reading from a file 208
Who moved my file? 210
Adding directory names to your filenames 211
Reading a line at a time 212
Closing the connection to a disk file 213
Defining Subclasses (What It Means to Be a Full-Time or Part-Time Employee) 214
Creating a subclass 216
Creating subclasses is habit-forming 219
Using Subclasses 219
Making types match 221
The second half of the story 222
Overriding Existing Methods (Changing the Payments for Some Employees) 224
A Java annotation 226
Using methods from classes and subclasses 226
Chapter 9: Constructing New Objects 231
Defining Constructors (What It Means to Be a Temperature) 232
What is a temperature? 233
What is a temperature scale? (Java’s enum type) 233
Okay, so then what is a temperature? 234
What you can do with a temperature 236
Calling new Temperature(32.0): A case study 239
Some things never change 241
More Subclasses (Doing Something about the Weather) 243
Building better temperatures 243
Constructors for subclasses 245
Using all this stuff 246
The default constructor 247
A Constructor That Does More 250
Classes and methods from the Java API 253
The SuppressWarnings annotation 254
Part 4: Smart Java Techniques 257
Chapter 10: Putting Variables and Methods Where They Belong 259
Defining a Class (What It Means to Be a Baseball Player) 260
Another way to beautify your numbers 261
Using the Player class 261
One class; nine objects 264
Don’t get all GUI on me 265
Tossing an exception from method to method 266
Making Static (Finding the Team Average) 267
Why is there so much static? 269
Meet the static initializer 270
Displaying the overall team average 271
The static keyword is yesterday’s news 273
Could cause static; handle with care 274
Experiments with Variables 277
Putting a variable in its place 277
Telling a variable where to go 280
Passing Parameters 285
Pass by value 285
Returning a result 287
Pass by reference 287
Returning an object from a method 289
Epilogue 292
Chapter 11: Using Arrays to Juggle Values 293
Getting Your Ducks All in a Row 293
Creating an array in two easy steps 296
Storing values 297
Tab stops and other special things 299
Using an array initializer 299
Stepping through an array with the enhanced for loop 300
Searching 302
Writing to a file 305
When to close a file 306
Arrays of Objects 307
Using the Room class 309
Yet another way to beautify your numbers 312
The conditional operator 313
Command Line Arguments 315
Using command line arguments in a Java program 317
Checking for the right number of command line arguments 319
Chapter 12: Using Collections and Streams (When Arrays Aren’t Good Enough) 321
Understanding the Limitations of Arrays 321
Collection Classes to the Rescue 323
Using an ArrayList 323
Using generics 325
Wrapper classes 328
Testing for the presence of more data 330
Using an iterator 330
Java’s many collection classes 331
Functional Programming 333
Solving a problem the old-fashioned way 336
Streams 338
Lambda expressions 339
A taxonomy of lambda expressions 342
Using streams and lambda expressions 342
Why bother? 348
Method references 350
Chapter 13: Looking Good When Things Take Unexpected Turns 351
Handling Exceptions 352
The parameter in a catch clause 356
Exception types 357
Who’s going to catch the exception? 359
Catching two or more exceptions at a time 365
Throwing caution to the wind 366
Doing useful things 367
Our friends, the good exceptions 368
Handle an Exception or Pass the Buck 369
Finishing the Job with a finally Clause 376
A try Statement with Resources 379
Chapter 14: Sharing Names among the Parts of a Java Program 383
Access Modifiers 384
Classes, Access, and Multipart Programs 385
Members versus classes 385
Access modifiers for members 386
Putting a drawing on a frame 389
Directory structure 391
Making a frame 392
Sneaking Away from the Original Code 394
Default access 396
Crawling back into the package 399
Protected Access 400
Subclasses that aren’t in the same package 400
Classes that aren’t subclasses (but are in the same package) 402
Access Modifiers for Java Classes 406
Public classes 406
Nonpublic classes 406
Chapter 15: Fancy Reference Types 409
Java’s Types 409
The Java Interface 410
Two interfaces 411
Implementing interfaces 412
Putting the pieces together 415
Abstract Classes 417
Caring for your pet 420
Using all your classes 422
Relax! You’re Not Seeing Double! 424
Chapter 16: Responding to Keystrokes and Mouse Clicks 427
Go On Click That Button 428
Events and event handling 430
Threads of execution 431
The keyword this 432
Inside the actionPerformed method 434
The serialVersionUID 435
Responding to Things Other Than Button Clicks 436
Creating Inner Classes 441
Chapter 17: Using Java Database Connectivity 445
Creating a Database and a Table 446
What happens when you run the code 447
Using SQL commands 447
Connecting and disconnecting 449
Putting Data in the Table 450
Retrieving Data 451
Destroying Data 453
Part 5: The Part of Tens 455
Chapter 18: Ten Ways to Avoid Mistakes 457
Putting Capital Letters Where They Belong 457
Breaking Out of a switch Statement 458
Comparing Values with a Double Equal Sign 458
Adding Components to a GUI 459
Adding Listeners to Handle Events 459
Defining the Required Constructors 459
Fixing Non-Static References 460
Staying within Bounds in an Array 460
Anticipating Null Pointers 461
Helping Java Find Its Files 462
Chapter 19: Ten Websites for Java 463
This Book’s Website 463
The Horse’s Mouth 463
Finding News, Reviews, and Sample Code 464
Got a Technical Question? 464
Index 465
