Performance myths about the Java platform abound, from the general "Java is slow", to the more specific "reflection is slow", "allocation is slow", "synchronization is slow", "garbage collection is slow", etc. Many of these myths have their root in fact (in JDK 1.0, everything was slow); today, not only are many of these statements not true, but Java performance has surpassed that of C in many areas, such as memory management.

In this class, we'll look at some common Java performance myths, identify where they came from, and explore the platform changes that have rendered them no longer true. Many common performance hacks don't actually help, and some can seriously hurt performance. The result is that clean code that follows common usage patterns generally shows far better behavior on modern JVMs than code laden with tweaks designed to "help" the JIT or garbage collector. More often than not, this well-intentioned assistance has the unfortunate effect of undermining many common JIT optimizations, resulting in slower -- not faster -- code.

The Java language included support for threads and concurrency from day 1, but writing correct multithreaded programs is not easy. This session will cover the how and why of using threads in Java.

Programming is hard, but concurrent programming is harder. Concurrent programs are at risk for all the safety, liveness, and performance hazards that sequential programs are. But there are also many hazards that apply exclusively to multithreaded programs, such as race conditions, stale data, and deadlock.

If an object is going to be accessed from multiple threads, it should be thread-safe. The requirement for thread-safety is often introduced into Java programs not by explicit use of threads within the program, but by the use of frameworks, such as Servlets and Swing, which create threads and call application components from those threads.

This class will cover what is thread safety, how to create thread-safe classes, and what costs and benefits you can expect to encounter by using threads in your programs.

JDK 5.0 is a huge step forward in developing concurrent Java classes and applications, providing a rich set of high-level concurrency building blocks.

Prior to the release of JDK 5.0, the Java platform provided basic primitives for writing concurrent programs, but they were just that -- primitive -- and difficult to use properly. Building multithreaded applications on the Java platform's low-level concurrency primitives posed many traps for the unwary, and many developers were forced to reinvent the wheel by writing their own classes for thread pools, semaphores, and task schedulers.

To help users create robust, scalable, and (most importantly) correct multithreaded applications, JDK 5.0 includes a rich set of high-level concurrency constructs, such as thread pools, semaphores, mutexes, barriers, and high-performance concurrent collection classes. Using these concurrency utilities will, in most cases, make your programs clearer, shorter, faster, easier to write, and more reliable. This session provides you with an overview of the new high-level concurrency utilities in the new java.util.concurrent package in JDK 5.0.

Does your program have bugs, despite unit tests, integration tests, and code reviews? You bet. Are you using static analysis as part of your QA process? If not, you're probably missing out on some bugs that can be caught before they bite your customers.

The cost of finding a bug increases dramatically the longer it lurks without being discovered. Fortunately, today?s development tools (IDEs and compilers) can identify many potential bugs within a few seconds of their creation, resulting in higher quality code and more productive programmers. However, even the best programmers can create bugs that are very hard to spot if they make it through their first few minutes of their existence.

Until recently, automated code analyzers have not been very useful for mainstream developers. Most code analysis packages focused either on stylistic issues (such as indenting and variable naming), or on formal correctness proofs (which require an investment in specification that few developers can afford to make.)

FindBugs, an open-source tool developed by Bill Pugh and David Hovermeyer of the University of Maryland, has raised the bar for ease-of-use and effectiveness of automated code analysis for finding bugs. FindBugs has been able to find many serious bugs in production software, including Eclipse, JBoss, Apache Tomcat and Sun's JDK implementation, with an impressively low false-positive rate compared to other approaches.

This session will explore how static code auditing tools work, how it is easy to write bug-detector plugins to find new bug patterns, presents some common bug patterns and fun "find the bug" puzzles, and shows how code auditing tools can easily identify them.

Every developer will want to have these tools in their toolbox.

What's the worst thing that can happen when you fail to synchronize in a concurrent Java program? Its probably worse than you think -- modern shared-memory processors can do some pretty weird things when left to their own devices.

Java was the first mainstream programming language to incorporate a formal, cross-platform memory model, which is what enabled the development of write-once, run-anywhere concurrent classes. It is the Java Memory model that defines the semantics of synchronized, volatile, and final.

However, because the most commonly used processors (Intel and Sparc) offer stronger memory models than is required by the JMM, many developers frequently use synchronization and volatile incorrectly, but have been insulated from failure by the stronger memory guarantees offered by the processor architecture they happen to be deploying on. (The infamous "double checked locking" idiom is an example of this sort of error.)

Understanding the Java Memory model is key to using the core concurrency primitives (synchronized and volatile) to develop thread-safe, efficient concurrent classes. We?ll cover what a memory model is (and why we should care), what synchronization really means, and what can really go wrong when we fail to synchronized correctly.