Thinking 
in 
Java 
Fourth Edition 
Bruce Eckel 
President, MindView, Inc.
                 teochew 
 
 
 
 
 
 
 
 
 
 
 
 
Comments from readers: 
Thinking In Java should be read cover to cover by every Java programmer, then kept close at 
hand for frequent reference. The exercises are challenging, and the chapter on Collections is 
superb! Not only did this book help me to pass the Sun Certified Java Programmer exam; it’s 
also the first book I turn to whenever I have a Java question. Jim Pleger, Loudoun 
County (Virginia) Government   
Much better than any other Java book I’ve seen. Make that “by an order of magnitude”... very 
complete, with excellent right-to-the-point examples and intelligent, not dumbed-down, 
explanations ... In contrast to many other Java books I found it to be unusually mature, 
consistent, intellectually honest, well-written and precise. IMHO, an ideal book for studying 
Java. Anatoly Vorobey, Technion University, Haifa, Israel   
One of the absolutely best programming tutorials I’ve seen for any language. Joakim 
Ziegler, FIX sysop   
Thank you for your wonderful, wonderful book on Java. Dr. Gavin Pillay, Registrar, King 
Edward VIII Hospital, South Africa   
Thank you again for your awesome book. I was really floundering (being a non-C 
programmer), but your book has brought me up to speed as fast as I could read it. It’s really 
cool to be able to understand the underlying principles and concepts from the start, rather 
than having to try to build that conceptual model through trial and error. Hopefully I will be 
able to attend your seminar in the not-too-distant future. Randall R. Hawley, 
Automation Technician, Eli Lilly & Co.   
The best computer book writing I have seen. Tom Holland   
This is one of the best books I’ve read about a programming language… The best book ever 
written on Java. Ravindra Pai, Oracle Corporation, SUNOS product line   
This is the best book on Java that I have ever found! You have done a great job. Your depth is 
amazing. I will be purchasing the book when it is published. I have been learning Java since 
October 96. I have read a few books, and consider yours a “MUST READ.” These past few 
months we have been focused on a product written entirely in Java. Your book has helped 
solidify topics I was shaky on and has expanded my knowledge base. I have even used some 
of your explanations as information in interviewing contractors to help our team. I have 
found how much Java knowledge they have by asking them about things I have learned from 
reading your book (e.g., the difference between arrays and Vectors). Your book is great! 
Steve Wilkinson, Senior Staff Specialist, MCI Telecommunications   
Great book. Best book on Java I have seen so far. Jeff Sinclair, Software Engineer, 
Kestral Computing   
Thank you for Thinking in Java. It’s time someone went beyond mere language description 
to a thoughtful, penetrating analytic tutorial that doesn’t kowtow to The Manufacturers. I’ve 
read almost all the others—only yours and Patrick Winston’s have found a place in my heart. 
I’m already recommending it to customers. Thanks again. Richard Brooks, Java 
Consultant, Sun Professional Services, Dallas    
Bruce, your book is wonderful! Your explanations are clear and direct. Through your 
fantastic book I have gained a tremendous amount of Java knowledge. The exercises are also 
FANTASTIC and do an excellent job reinforcing the ideas explained throughout the chapters. 
I look forward to reading more books written by you. Thank you for the tremendous service 
that you are providing by writing such great books. My code will be much better after reading 
Thinking in Java. I thank you and I’m sure any programmers who will have to maintain my 
code are also grateful to you. Yvonne Watkins, Java Artisan, Discover Technologies, 
Inc.   
Other books cover the WHAT of Java (describing the syntax and the libraries) or the HOW of 
Java (practical programming examples). Thinking in Java is the only book I know that 
explains the WHY of Java; why it was designed the way it was, why it works the way it does, 
why it sometimes doesn’t work, why it’s better than C++, why it’s not. Although it also does a 
good job of teaching the what and how of the language, Thinking in Java is definitely the 
thinking person’s choice in a Java book. Robert S. Stephenson   
Thanks for writing a great book. The more I read it the better I like it. My students like it, too. 
Chuck Iverson   
I just want to commend you for your work on Thinking in Java. It is people like you that 
dignify the future of the Internet and I just want to thank you for your effort. It is very much 
appreciated. Patrick Barrell, Network Officer Mamco, QAF Mfg. Inc.   
I really, really appreciate your enthusiasm and your work. I download every revision of your 
online books and am looking into languages and exploring what I would never have dared 
(C#, C++, Python, and Ruby, as a side effect). I have at least 15 other Java books (I needed 3 
to make both JavaScript and PHP viable!) and subscriptions to Dr. Dobbs, JavaPro, JDJ, 
JavaWorld, etc., as a result of my pursuit of Java (and Enterprise Java) and certification but I 
still keep your book in higher esteem. It truly is a thinking man’s book. I subscribe to your 
newsletter and hope to one day sit down and solve some of the problems you extend for the 
solutions guides for you (I’ll buy the guides!) in appreciation. But in the meantime, thanks a 
lot. Joshua Long, www.starbuxman.com   
Most of the Java books out there are fine for a start, and most just have beginning stuff and a 
lot of the same examples. Yours is by far the best advanced thinking book I’ve seen. Please 
publish it soon! ... I also bought Thinking in C++ just because I was so impressed with 
Thinking in Java. George Laframboise, LightWorx Technology Consulting, Inc.   
I wrote to you earlier about my favorable impressions regarding your Thinking in C++ (a 
book that stands prominently on my shelf here at work). And today I’ve been able to delve 
into Java with your e-book in my virtual hand, and I must say (in my best Chevy Chase from 
Modern Problems), “I like it!” Very informative and explanatory, without reading like a dry 
textbook. You cover the most important yet the least covered concepts of Java development: 
the whys. Sean Brady   
I develop in both Java and C++, and both of your books have been lifesavers for me. If I am 
stumped about a particular concept, I know that I can count on your books to a) explain the 
thought to me clearly and b) have solid examples that pertain to what I am trying to 
accomplish. I have yet to find another author that I continually whole-heartedly recommend 
to anyone who is willing to listen. Josh Asbury, A^3 Software Consulting, Cincinnati, 
Ohio   
Your examples are clear and easy to understand. You took care of many important details of 
Java that can’t be found easily in the weak Java documentation. And you don’t waste the 
reader’s time with the basic facts a programmer already knows. Kai Engert, Innovative 
Software, Germany   
I’m a great fan of your Thinking in C++ and have recommended it to associates. As I go 
through the electronic version of your Java book, I’m finding that you’ve retained the same 
high level of writing. Thank you! Peter R. Neuwald  
VERY well-written Java book...I think you’ve done a GREAT job on it. As the leader of a 
Chicagoarea Java special interest group, I’ve favorably mentioned your book and Web site 
several times at our recent meetings. I would like to use Thinking in Java as the basis for a 
part of each monthly SIG meeting, in which we review and discuss each chapter in 
succession. Mark Ertes   
By the way, printed TIJ2 in Russian is still selling great, and remains bestseller. Learning 
Java became synonym of reading TIJ2, isn’t that nice? Ivan Porty, translator and 
publisher of Thinking in Java 2nd Edition in Russian   
I really appreciate your work and your book is good. I recommend it here to our users and 
Ph.D. students. Hugues Leroy // Irisa-Inria Rennes France, Head of Scientific 
Computing and Industrial Tranfert   
OK, I’ve only read about 40 pages of Thinking in Java, but I’ve already found it to be the 
most clearly written and presented programming book I’ve come across...and I’m a writer, 
myself, so I am probably a little critical. I have Thinking in C++ on order and can’t wait to 
crack it—I’m fairly new to programming and am hitting learning curves head-on everywhere. 
So this is just a quick note to say thanks for your excellent work. I had begun to burn a little 
low on enthusiasm from slogging through the mucky, murky prose of most computer books—
even ones that came with glowing recommendations. I feel a whole lot better now. Glenn 
Becker, Educational Theatre Association   
Thank you for making your wonderful book available. I have found it immensely useful in 
finally understanding what I experienced as confusing in Java and C++. Reading your book 
has been very satisfying. Felix Bizaoui, Twin Oaks Industries, Louisa, Va.   
I must congratulate you on an excellent book. I decided to have a look at Thinking in Java 
based on my experience with Thinking in C++, and I was not disappointed. Jaco van der 
Merwe, Software Specialist, DataFusion Systems Ltd, Stellenbosch, South Africa   
This has to be one of the best Java books I’ve seen. E.F. Pritchard, Senior Software 
Engineer, Cambridge Animation Systems Ltd., United Kingdom   
Your book makes all the other Java books I’ve read or flipped through seem doubly useless 
and insulting. Brett Porter, Senior Programmer, Art & Logic   
I have been reading your book for a week or two and compared to the books I have read 
earlier on Java, your book seems to have given me a great start. I have recommended this 
book to a lot of my friends and they have rated it excellent. Please accept my congratulations 
for coming out with an excellent book. Rama Krishna Bhupathi, Software Engineer, 
TCSI Corporation, San Jose   
Just wanted to say what a “brilliant” piece of work your book is. I’ve been using it as a major 
reference for in-house Java work. I find that the table of contents is just right for quickly 
locating the section that is required. It’s also nice to see a book that is not just a rehash of the 
API nor treats the programmer like a dummy. Grant Sayer, Java Components Group 
Leader, Ceedata Systems Pty Ltd, Australia   
Wow! A readable, in-depth Java book. There are a lot of poor (and admittedly a couple of 
good) Java books out there, but from what I’ve seen yours is definitely one of the best. John 
Root, Web Developer, Department of Social Security, London   
I’ve just started Thinking in Java. I expect it to be very good because I really liked Thinking 
in C++ (which I read as an experienced C++ programmer, trying to stay ahead of the curve) 
… You are a wonderful author. Kevin K. Lewis, Technologist, ObjectSpace, Inc.   
I think it’s a great book. I learned all I know about Java from this book. Thank you for 
making it available for free over the Internet. If you wouldn’t have I’d know nothing about 
Java at all. But the best thing is that your book isn’t a commercial brochure for Java. It also 
shows the bad sides of Java. YOU have done a great job here. Frederik Fix, Belgium   
I have been hooked to your books all the time. A couple of years ago, when I wanted to start 
with C++, it was C++ Inside & Out which took me around the fascinating world of C++. It 
helped me in getting better opportunities in life. Now, in pursuit of more knowledge and 
when I wanted to learn Java, I bumped into Thinking in Java—no doubts in my mind as to 
whether I need some other book. Just fantastic. It is more like rediscovering myself as I get 
along with the book. It is just a month since I started with Java, and heartfelt thanks to you, I 
am understanding it better now. Anand Kumar S., Software Engineer, 
Computervision, India   
Your book stands out as an excellent general introduction. Peter Robinson, University of 
Cambridge Computer Laboratory   
It’s by far the best material I have come across to help me learn Java and I just want you to 
know how lucky I feel to have found it. THANKS! Chuck Peterson, Product Leader, 
Internet Product Line, IVIS International   
The book is great. It’s the third book on Java I’ve started and I’m about two-thirds of the way 
through it now. I plan to finish this one. I found out about it because it is used in some 
internal classes at Lucent Technologies and a friend told me the book was on the Net. Good 
work. Jerry Nowlin, MTS, Lucent Technologies   
Of the six or so Java books I’ve accumulated to date, your Thinking in Java is by far the best 
and clearest. Michael Van Waas, Ph.D., President, TMR Associates   
I just want to say thanks for Thinking in Java. What a wonderful book you’ve made here! Not 
to mention downloadable for free! As a student I find your books invaluable (I have a copy of 
C++ Inside Out, another great book about C++), because they not only teach me the how-to, 
but also the whys, which are of course very important in building a strong foundation in 
languages such as C++ or Java. I have quite a lot of friends here who love programming just 
as I do, and I’ve told them about your books. They think it’s great! Thanks again! By the way, 
I’m Indonesian and I live in Java. Ray Frederick Djajadinata, Student at Trisakti 
University, Jakarta   
The mere fact that you have made this work free over the Net puts me into shock. I thought 
I’d let you know how much I appreciate and respect what you’re doing. Shane 
LeBouthillier, Computer Engineering student, University of Alberta, Canada   
I have to tell you how much I look forward to reading your monthly column. As a newbie to 
the world of object oriented programming, I appreciate the time and thoughtfulness that you 
give to even the most elementary topic. I have downloaded your book, but you can bet that I 
will purchase the hard copy when it is published. Thanks for all of your help. Dan Cashmer, 
B. C. Ziegler & Co.   
Just want to congratulate you on a job well done. First I stumbled upon the PDF version of 
Thinking in Java. Even before I finished reading it, I ran to the store and found Thinking in 
C++. Now, I have been in the computer business for over eight years, as a consultant, 
software engineer, teacher/trainer, and recently as self-employed, so I’d like to think that I 
have seen enough (not “have seen it all,” mind you, but enough). However, these books cause 
my girlfriend to call me a ”geek.” Not that I have anything against the concept—it is just that I 
thought this phase was well beyond me. But I find myself truly enjoying both books, like no 
other computer book I have touched or bought so far. Excellent writing style, very nice 
introduction of every new topic, and lots of wisdom in the books. Well done. Simon 
Goland, simonsez@smartt.com, Simon Says Consulting, Inc.   
I must say that your Thinking in Java is great! That is exactly the kind of documentation I 
was looking for. Especially the sections about good and poor software design using Java. 
Dirk Duehr, Lexikon Verlag, Bertelsmann AG, Germany   
Thank you for writing two great books (Thinking in C++, Thinking in Java). You have helped 
me immensely in my progression to object oriented programming. Donald Lawson, DCL 
Enterprises   
Thank you for taking the time to write a really helpful book on Java. If teaching makes you 
understand something, by now you must be pretty pleased with yourself. Dominic Turner, 
GEAC Support   
It’s the best Java book I have ever read—and I read some. Jean-Yves MENGANT, Chief 
Software Architect NAT-SYSTEM, Paris, France   
Thinking in Java gives the best coverage and explanation. Very easy to read, and I mean the 
code fragments as well. Ron Chan, Ph.D., Expert Choice, Inc., Pittsburgh, Pa.   
Your book is great. I have read lots of programming books and your book still adds insights 
to programming in my mind. Ningjian Wang, Information System Engineer, The 
Vanguard Group   
Thinking in Java is an excellent and readable book. I recommend it to all my students. Dr. 
Paul Gorman, Department of Computer Science, University of Otago, Dunedin, 
New Zealand   
With your book, I have now understood what object oriented programming means. ... I 
believe that Java is much more straightforward and often even easier than Perl. Torsten 
Römer, Orange Denmark   
You make it possible for the proverbial free lunch to exist, not just a soup kitchen type of 
lunch but a gourmet delight for those who appreciate good software and books about it. Jose 
Suriol, Scylax Corporation   
Thanks for the opportunity of watching this book grow into a masterpiece! IT IS THE BEST 
book on the subject that I’ve read or browsed. Jeff Lapchinsky, Programmer, Net 
Results Technologies   
Your book is concise, accessible and a joy to read. Keith Ritchie, Java Research & 
Development Team, KL Group Inc.   
It truly is the best book I’ve read on Java! Daniel Eng   
The best book I have seen on Java! Rich Hoffarth, Senior Architect, West Group   
Thank you for a wonderful book. I’m having a lot of fun going through the chapters. Fred 
Trimble, Actium Corporation   
You have mastered the art of slowly and successfully making us grasp the details. You make 
learning VERY easy and satisfying. Thank you for a truly wonderful tutorial. Rajesh Rau, 
Software Consultant   
Thinking in Java rocks the free world! Miko O’Sullivan, President, Idocs Inc.  
 
 
About Thinking in C++: 
 
Winner of the 1995 Software Development Magazine Jolt Award for Best Book of 
the Year 
 
“This book is a tremendous achievement. You owe it to yourself to have a copy on your 
shelf. The chapter on iostreams is the most comprehensive and understandable 
treatment of that subject I’ve seen to date.” 
Al Stevens 
Contributing Editor, Doctor Dobbs Journal 
 
“Eckel’s book is the only one to so clearly explain how to rethink program construction 
for object orientation. That the book is also an excellent tutorial on the ins and outs of 
C++ is an added bonus.” 
Andrew Binstock 
Editor, Unix Review 
 
“Bruce continues to amaze me with his insight into C++, and Thinking in C++ is his best 
collection of ideas yet. If you want clear answers to difficult questions about C++, buy 
this outstanding book.” 
Gary Entsminger 
Author, The Tao of Objects 
 
“Thinking in C++ patiently and methodically explores the issues of when and how to use 
inlines, references, operator overloading, inheritance, and dynamic objects, as well as 
advanced topics such as the proper use of templates, exceptions and multiple 
inheritance. The entire effort is woven in a fabric that includes Eckel’s own philosophy of 
object and program design. A must for every C++ developer’s bookshelf, Thinking in 
C++ is the one C++ book you must have if you’re doing serious development with C++.” 
Richard Hale Shaw 
Contributing Editor, PC Magazine 
 
 
 
 
 
 
 
 
 
 
 
Thinking 
in 
Java 
Fourth Edition 
Bruce Eckel 
President, MindView, Inc. 
 
 
Upper Saddle River, NJ ● Boston ● Indianapolis ● San Francisco 
New York ● Toronto ● Montreal ● London ● Munich ● Paris 
Madrid ● Capetown ● Sydney ● Tokyo ● Singapore ● Mexico City