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Bio: Joshua Bloch, Google's chief Java architect and a former Distinguished Engineer at Sun Microsystems, won the prestigious Jolt Award from Software Development Magazine for his book, Effective Java Programming Language Guide. At Sun, he led the design and implementation of numerous Java platform features, including JDK 5.0 language enhancements and the award-winning Java Collections Framework. He holds a Ph.D. in computer science from Carnegie-Mellon University and is most recently the co-author, with Neal Gafter, of Java Puzzlers.
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Q: I've heard that at your doctoral thesis defense at Carnegie-Mellon, which was open to anyone for questions, you planted a long technical question with your mother that you answered flawlessly after saying, "Awww, Mom!" Is that true?
A:Yes. The question appeared to tear the work to shreds. My mom had fun with it, and so did I. Thesis defenses can be so dry. I did everything I could to inject a bit of levity into mine. I also answered another -- planted -- question with a rap, complete with recorded rhythm track. I had a boom box concealed under the desk during the talk.
Q: You are currently busy revising Effective Java. Can you give us some hints about what will be in the second edition?
A: I'm trying very hard to preserve the tone of the first edition. I'm revising all the existing items in light of the J2SE 5.0 language changes and everything I've learned since 2001. I'm adding a few more items here and there, plus an entire chapter on generics. Also, I'm slanting the threads chapter toward java.util.concurrent.
Q: What are the most interesting or funny reactions you have gotten from readers of Java Puzzlers?
A: Well, I got a letter from David Bacon thanking me for the copy I sent him and saying that it was the perfect thickness to raise his monitor up to the correct height. Then he sent me a picture of his intern's monitor with a copy of the book under it. I also thought it was pretty funny when our Japanese translator, Yoshiki Shibata, caught us falling into one of our own traps. It's described here, if you're curious.
Q: In June 2004, when you became chief Java architect at Google, you were put in charge of spreading and encouraging the use of Java technology there. How has it gone?
A: Very well indeed. We use the Java platform extensively in many of our products and internal applications. Of course, we use other languages too.
Q: Some people may not know that you identified a widespread bug affecting both Java and other languages that had gone unnoticed for half a century. Tell us about it.
A: It wasn't really half a century. A quarter century maybe. And I
didn't really identify it -- I propagated it into the Java platform
libraries! Someone reported the bug to Sun. I don't know who it was, but I was shocked -- and amused -- by the bug. At Peter Norvig's
urging, I wrote it up for the Google research blog. I guess it caused quite a stir in the blogosphere.
Q: How do you feel about the open sourcing of the Java platform?
A: I think it's a good thing. It goes a long way toward easing the concerns of the open-source and research communities about the legal aspects of working with the platform. In many ways, it's always been a pretty open platform: free access to the source code, heck, even the bug database. But it's nice that Sun has gone all the way.
Q: What advice would you give to a programmer new to the Java language?
A: Write lots of code. Have fun with it! Collaborate with people who are more experienced than you and learn from them. Join an open-source project. Code reviews are a great way to learn. Don't be embarrassed when people find problems in your code. Fix them and have fun watching your code and your skills improve. Oh, yeah, and go buy a copy of Effective Java.
Q: What do you think is the most inventive use of Java technology?
A: That's another tough one. I guess you can't go too far wrong with
the Mars Rover. I was
blown away by the images that it transmitted.
Q: What's the biggest misconception about Java technology?
A: What irks me most is that there are still people who think it's slow. That's ancient history. By J2SE 1.4, the platform was not appreciably slower than traditional compiled languages, and it just keeps getting faster. Both of the last two releases were impressive in this regard. You don't have to touch your program. Just download the new release, and your program will run significantly faster.
Q: The Java class that you couldn't live without is...?
A: I'm going to have to say LinkedHashMap, even if I did write it. It combines the speed of HashMap with the predictability of a sorted map.
Q: What's your favorite Java technology book?
A: Modesty prevents me from answering this one directly, so I'll plug one of my favorite programming books that isn't specific to the Java language. Anyone who cares at all about bit twiddling should get their hands on Henry S. Warren's Hacker's Delight. It's the Bible of bit twiddling.
Another book that every programmer should read is Jon Bentley's Programming Pearls. It's a great book about "programming in the small," as relevant today as when it was first published in 1986.
Q: Can you describe the process of writing code?
A: For me, there are several distinct stages. The hardest part is figuring out what problem I'm really trying to solve. Once I do that, it's usually reasonably straightforward to envision the rough outlines of the solution. Then it's a "simple matter of programming" to make it real, including the tests, of course.
Q: What's the next big technology revolution?
A: I'm really bad at predicting the future. It's clear that multicore machines will be mainstream in the very near future and that programs will have to change to take full advantage of them. I'm not betting on Software Transactional Memories (STMs) in the near term, but on high-quality multithreaded utilities, such as java.util.concurrent. Oh, yeah, and everything that isn't already on the web will be soon.
Q: What do you see as the most important Java technology API five years from now?
A: The core APIs -- java.lang and java.util -- will still be very important. But java.util.concurrent and its offspring will be equally important.
Q: If you could work on a dream project, what would it be?
A: A brand-new Java-like language atop the same virtual machine that is not compatible with the Java programming language. Rather than shoving yet more features into this language, I want a fresh start, but I want to leverage much of the work that has already gone into the platform. That means using the same virtual machine and providing some interoperability story with existing libraries.
Q: What recent changes to the platform have made your life easier?
A: I hate to sound like a broken record, but java.util.concurrent. Also java.util.ArrayDeque and NavigableMap. The for-each loop is great, and so are generics, even if they do complicate things somewhat.
Q: Where in the process of programming do you have the most fun?
A: I enjoy many phases, from requirements analysis to debugging. Each of these phases presents me with brainteasers, and solving these brainteasers is what I like best. But nothing makes me feel better than building a reusable component and seeing it get reused.
For More Information
Vodcast: Joshua Bloch and Neal Gafter, Authors of Java Puzzlers
Seeing Shouldn't Be Believing: Interview With Josh Bloch and Neal Gafter
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