Reporting on the JavaOneSM Conference session "High-Performance GUIs with the Java Foundation Classes (JFC) API," Dana Nourie notes that GUI programs written using the JavaTM programming language have a reputation for rendering slowly or incorrectly. Nourie says developers can resolve these problems with coding techniques, however, by proper use of threads, and the new JavaTM 2 Platform, Standard Edition (J2SETM) 1.4 acceleration capabilities.

Panelist Steve Wilson, engineering manager at Sun, said "The cause behind slow rendering applications is not the Java programming language itself, but instead may include other causes such as programming techniques not taking advantage of the many benefits of the Java platform."

Among the remedies that Wilson proposes in his book "JavaTM Platform Performance Strategies and Tactics" are the following:

• Code with proper building techniques

• Make proper use of threads

• Take advantage of the new EventHandler, RepaintManager and the VolatileImage classes

The full source includes an example of code that, while it works, does not run efficiently. The proposed solution saves programming time and cuts down on both event object creation and runtime. Wilson recommends performing operations in bulk to reduce the number of events that are posted and initializing or totally replacing the contents of a model by constructing a new one instead of reusing the existing one.

The panelists also recommended using the event-dispatching thread instead of single-threaded event processing to exploit the savings available from using the paint and actionPerformed methods and the AWT EventQueue.invokeLater method. Any program that uses separate worker threads to perform GUI-related processing can use invokeLater and invokeAndWait methods to cause a Runnable object to be run on the event-dispatching thread.

Rendering complex shapes and patterns requires iterating through pixels and calculating values for each of them. Loading an image and performing a filter operation on it sometimes requires allocating a large block of memory. The new VolatileImage class in J2SE 1.4 allows programmers to create a hardware-accelerated offscreen image and manage the contents of that image. The new hardware acceleration has improved the performance of Swing applications because double-buffering now uses VolatileImage.

Applications can also be sped up by the use of methods and new classes. For example, repainting small regions instead of entire sections or screens can make a significant difference in the performance of an application. In addition to using paint methods correctly, putting the new EventHandler class from J2SE 1.4 to work will provide support for dynamically generating event listeners that have a small footprint and can be saved automatically by the persistence scheme. This can improve start-up as well. [...read more...]

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