OReilly hardcore java mar 2004 ISBN 0596005687

Nutshell Handbook, the Nutshell Handbook logo, and the O'Reilly logo are registered trademarks of O'Reilly Media, Inc.The Java Series, Hardcore Java, the image of a lion, and relatedtrad

difficult but extremely powerful and useful programming techniques like reflection,

advanced data modeling, advanced GUI

design, and advanced aspects of JDO, EJB

and XML-based web clients This unique book reveals the true wizardry behind the complex and often-mysterious Java environment.

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Studying a computer language is a career-long process Manydevelopers make the mistake of thinking that they have learnedenough They get caught in the corporate cycle of build-and-deploy and don't seek to expand their knowledge However, wecan hardly blame them for that

For one, the build-and-deploy cycle is intensive and carries with

it a substantial amount of political pressure: managers don'twant you to spend days reading a book or trying out code

turnaround, and you get to spend more time playing Frisbeewith your dog

The second problem that the corporate developer has to dealwith is that the majority of computer books are often not

appropriate for the intermediate to advanced developer Whenlooking at my rather impressive computer book library, much of

it from O'Reilly, I notice that my books tend to fall into two

categories: many are introductions to concepts and most of theothers are references to concepts Although these books arevery useful, there is a distinct lack of books that target the

intermediate to advanced programmer However, there is oneshining exception in my library

In a dusty corner of my desk is a book I bought several years

Limited) is absolutely essential for an intermediate C++

developer It begins with the assumption that you know thelanguage and then expands from there The result is a bookthat can really transform a developer from the intermediatelevel to a true guru

That is the goal of this book with regards to the Java™

language Most of the material is meant to help you avoid manycommon mistakes made by Java developers We will also covernuances of Java, idiosyncrasies of the JDK, and advanced

techniques With luck, this book will increase your productivityand your enjoyment of Java development

This book is for the intermediate to advanced Java programmer.With that in mind, we can concentrate on the knowledge andtechniques that go into some of the most advanced Java

software available

Prerequisites and Assumptions

Functional proficiency with Java

I will largely gloss over entire areas of Java I assume thatyou understand JavaBeans™, bound properties, JDBC, andother basics

Familiarity with basic computer science

I generally won't spend a lot of time on concepts such asscoping, logic operations, inheritance, and algorithm

construction These and similar concepts will be the basisfor more detailed discussions

Familiarity with UML

The Unified Modeling Language is the best way to expressobject-oriented engineering concepts in a manner that isfamiliar to all programmers, regardless of what languagethey speak Most of the code diagrams in this book

incorporate UML

You should be familiar with the JDK and with how to compile

a program and use its various tools in the JDK However,expertise in all packages isn't necessary

Used for commands you enter at the command line and tohighlight new code inserted in a running example

This icon designates a note, which is an important aside to the nearby text.

This icon designates a warning.

The code sample set for this book is massive Almost every

snippet of code from the book can be found in the downloadablesource code (http://www.oreilly.com/catalog/hardcorejv)

However, without a guide, you could get lost quickly when

surfing through the examples

Regarding the code itself, I will frequently snip out pieces youwould need to get the code to compile and run Copying thisinfrastructure code in the book would add unnecessary bulk andpotentially cloud the issue being discussed Since I assume youare experienced in Java, I will also assume you know the

housekeeping procedures used to implement pertinent

concepts

One other tactic that I commonly use is to append a number tothe name of a class or method This is designed to show

successive versions of the same class or method The goal is toemphasize the development while allowing the user to look upthe old version and play with it if he chooses For example, youshould read Country4 as Country

Finally, the code samples are very well-documented However,for brevity's sake, I will usually slice out this documentationwhen presenting code examples Although I firmly believe thatgood Javadoc documentation is important to good development,

in this book such documentation would needlessly increase thepage count without adding to the discussion

One other thing to note about the examples is that you will

often see the comment //$NON-NLS-1$ imbedded within thecode This is merely a flagging comment that tells Eclipse not tointernationalize a particular String I have snipped these

comments from the book, as they aren't relevant to the

discussions

combine several examples from a single subject into one classfile to reduce the housekeeping code needed to run the sample.Doing a search on the method name will quickly locate the citedexample

Categories of Examples

The examples themselves can be divided into three categories.Each of these categories has a different usage paradigm thatyou should be aware of

init:

[javac] Compiling 1 source file to C:\dev\hcj\bin

[javac] C:\dev\hcj\src\oreilly\hcj\review\RTTIDemo.java:54: incompatible types [javac] found : oreilly.hcj.review.RTTIDemo.A

[javac] required: oreilly.hcj.review.RTTIDemo.B

[javac] b = (A)a1; // compiler error: a1 is not a B

[javac] ^

[javac] C:\dev\hcj\src\oreilly\hcj\review\RTTIDemo.java:55: inconvertible types [javac] found : oreilly.hcj.review.RTTIDemo.C

java.lang.Object

[java] class oreilly.hcj.review.ObjectIsGod$SomeOtherClass |> class java.lang.Object

Total time: 1 second

Although this is the actual output, most of it is trivial and

common to every use of Ant Therefore, I snip out all of thishousekeeping for the sake of brevity The emphasized lines will

be taken out when the run is presented in the book Therefore,when you run the examples, be aware that Ant is a bit moreverbose than I am

One of the most important skills in professional development isknowing how to use tools There are a wide variety of tools

blown IDEs that do everything for you Selecting the best toolsfor the job will make you a more productive developer

available, from the standard text editor and compiler to full-UML Diagramming

For creating diagrams in UML, I use a product called Magic DrawUML, by No Magic, Inc (http://www.magicdraw.com/) This tool

is, without a doubt, the best professional UML modeling tool onthe market Rational Rose and Together can't even touch thefunctionality and quality of Magic Draw I like it so much that Ibought a copy of the Enterprise edition for myself I highly

recommend this product Although it isn't free like other tools Irecommend, it is well worth the price

IDE

The IDE I use is Eclipse 3.0M4, which happens to be the IDE Iuse professionally as well Eclipse simply has the single bestdevelopment tool on the market I don't know how I could livewithout my refactoring tools and the other goodies that comewith Eclipse You can find Eclipse at http://www.eclipse.org/.Also, I use many Eclipse plug-ins to make my job easier Theycan be found in the Community section of eclipse.org, or youcan surf the best directory of Eclipse plug-ins at http://eclipse-plugins.2y.net/eclipse/index.jsp

For building outside of my IDE and running examples, I useApache Ant 1.5, which is available from http://ant.apache.org/.Ant is simply the best make program ever invented I take myhat of to the folks at Apache

Logging

I use Jakarta Log4J to do logging in my programs Log4J is

available from http://jakarta.apache.org/log4j/docs/index.html

In much of the sample code, there is little logging However, inproduction systems, I am a logging fanatic

For those of you that are curious, I don't use the JDK 1.4 logging mechanism because it is, in my opinion, vastly inferior to Log4J on many levels.

Jakarta Commons

Another set of libraries that I often use in my professional code

is the Jakarta Commons Libraries These libraries are availablefrom http://jakarta.apache.org/commons/index.html They

code itself If you haven't checked out the Commons Libraries, Istrongly advise you to do so.

This book is here to help you get your job done In general, youmay use the code in this book in your programs and

documentation You do not need to contact O'Reilly for

permission unless you're reproducing a significant portion of thecode For example, writing a program that uses several chunks

of code from this book does not require permission Selling or

distributing a CD-ROM of examples from O'Reilly books does

require permission Answering a question by citing this bookand quoting example code does not require permission

Incorporating a significant amount of example code from this

book into your product's documentation does require

permission

We appreciate, but do not require, attribution An attributionusually includes the title, author, publisher, and ISBN For

example: "Hardcore Java, by Robert Simmons, Jr Copyright

2001 O'Reilly Media, Inc., 0-596-00568-7."

If you feel your use of code examples falls outside fair use orthe permission given above, feel free to contact us at

permissions@oreilly.com.

Please address comments and questions concerning this book tothe publisher:

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I would like to thank all of the thousands of people who haveanswered my endless questions over the years in my quest tobecome a professional software engineer Without these

anonymous thousands on the Internet, the path would havebeen much more difficult

I would also like to thank all of the junior programmers thathave worked for me and kept my eyes open to new ideas There

is nothing like a fresh mind to suggest things that are radical,untried, and, in the end, brilliant Certain people leap to mind,such as Bettina Linssen, now a senior developer Even though Ihad considered myself something of a guru in Java GUI coding,her fresh insight and ideas taught me a thing or two All yousenior developers out there would be well advised to listen tothe ideas of your junior developers You never know what theymight teach you

I would also like to extend very special thanks to Marco

Kukulies Marco started his programming career as a junior

developer working for me He excelled beyond all expectationsand demonstrated that he has that special gift that separatesthe normal programmers from the true gurus Marco is now one

understand much of my work, without his and Marco Kukulies'moral support, this book simply wouldn't have happened My

Sa ir's wife Mirsada, and his three children Aida, Selma, andAmela Thanks for being a second family to me!

I would like to take a moment to say "Hi" to my brother Pauland my sister Debbie I currently live in Germany, and although

electronic chapters Just look for the hand reaching up

frantically for help His editing prowess has increased the

quality of my work to a level I never knew possible When I

proposed this book to O'Reilly, it was in a much rougher statethan it is now With many publishers, I would have been mostly

on my own However, O'Reilly has really worked hard to help

me make this book one that I can be proud of I have learned alot, and Brett has truly converted me from a newbie author to aprofessional

I can hear the groans from herea review on Java? Don't worry, Iwon't bore you with all of the gory syntax details or concepts ofthe Java language that you can easily pick up in other books.Instead, I will present a conceptual review that focuses on

some various important issues that are often overlooked or

underemphasized The study of these issues will not only giveyou a better understanding of the Java language, but prepareyou for what's covered in the rest of the book You should think

of this chapter as a roving spotlight, highlighting various issues

of Java that are worthy of mention; even the intermediate andadvanced programmer will benefit from the study of these

issues

To understand the advanced concepts of the Java language,there are a few core concepts that you must have firmly in

mind Without these concepts, much of this book will not make

a lot of sense The concepts of pointers in Java, its class

hierarchy, and RTTI (runtime type identification) are three ofthe most important on this list

1.1.1 Constant Problems with Pointers

Java and C++ use a very analogous syntax to symbolize theirinstructions to the computer's CPU In fact, there are probablymore similarities between these languages than the two

entrenched camps of supporters would like to admit One

difference between Java and C++ that is often mentioned,

though, is that Java does not use pointers.

Pointers in C++ were a constant source of problems and weredetermined to be the programming equivalent of evil incarnate.There was, and is to this day, a large group of applications inC++ that suffer from the effects of this particular wrong

Therefore, Sun decided to leave them out of Javaat least that'sthe theory

In reality, Java uses what C++ calls references In fact, other

than primitives, all variables in Java are references Referencesand pointers are very similar; both contain the memory location

of a particular object Pointers, however, allow you to do

arithmetic whereas references do not The fact that Java uses

so many references introduces some difficulties that novice andproficient Java developers often get burned by The code shown

in Example 1-1 demonstrates one of these difficulties

vector itself Since both variables now point to the same vector,this function actually adds an element to the source vector thatwas passed into the method; this was almost certainly not thedesired effect! We will discuss how to prevent this problem in

Chapter 2

Since you can change the contents of an incoming collection,Java actually does have pointersthat is, Java references embodythe same computer science principles that pointers do So,

when someone tells you that Java doesn't have pointers, youcan correct them by saying, "Java has pointers, it just doesn'thave pointer arithmetic."

Also, Java's use of references isn't a bad thing In fact, the

references are actually necessary to the Java language Withoutthem, you would have to pass everything by value This would

passed to a method If the object were a String, this copyingprobably wouldn't be a big deal However, if the object is a largearray or set, the copy could take a long time Therefore,

passing everything by value would make Java code run

extremely slowly Furthermore, some objects simply don't makesense to copy at all If you have a GUI panel and wish to passthe GUI panel to another component that needs to refer to it,you certainly don't want two copies of the panel floating around

types, such as int and boolean; and even these primitive typescan be treated as objects under some circumstances, such aswhen you use reflection

I would expect that most Java programmers would find this

trivial since they already know that every nonprimitive in Java is

an object The point that I am really trying to make, though, isthat every constructed type in Java descends from the class

There are three main reasons why java.lang.Object is always

tool With RTTI, objects become very friendly and readily tellyou what they are, how they are used, and more In Java, RTTI

is built right into the core of the virtual machine You've almostcertainly used RTTI, even if you don't realize it; it's all over theplace For example, consider that every object in Java can tellyou what type it is through the getClass( ) method Wheneveryou invoke getClass( ), you use RTTI Example 1-4 shows the

[javac] b = (A)a1; // compiler error: a1 is not a B

[javac] ^

[javac] C:\dev\hcj\src\oreilly\hcj\review\RTTIDemo.java:55: inconvertible types [javac] found : oreilly.hcj.review.RTTIDemo.C

before dereferencing inner As long as inner isn't null, the

method checks to see whether the set contains target This

altered by any other evaluation, the remaining evaluations areskipped

1.2.2 Ternary Expressions

Ternary expressions look a little strange at first However, theycan be useful in making code read better For example, considerthe following code:

Ternary statements are very useful for performing evaluationssuch as this However, you have to be aware of a few gotchas.For example, the following code will not work:

In this statement, the user wants to make an if-then clause

because the return of the println( ) method is void

Additionally, the statement return p.x + p.y is pure

syntactical nonsense because return is a keyword that doesn'tevaluate to anything

Although ternary expressions are useful for shortening whatwould be an otherwise long and drawn-out piece of code, theycan be cryptic to read if they are abused I recommend that youuse ternary expressions only for very small evaluations If yourevaluation is complex, you are better off going with the if-then

structure

1.2.3 Leveraging for Loops

The for loop is one of the most elegant and underused loopingstructures in the Java language Most developers use only thebasic concept of a for loop to iterate through a predefined

for loop to make your code more elegant while dealing withsome annoying programming issues

Although the techniques in this section are not necessarily

required, they do make your code look a lot nicer However, ifthere is one concept that you should take from this section, it'sthat for loops can do much more than simply cycle through