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Java memory management
Are memory leaks possible, preventable in Java?
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Ideally of course, programmers would design applications with objects' lifecycles in mind, rather than rely on clever features of state-of-the-art JVM implementations.
In conclusion: Design problems can be mitigated by letting go of object references in one's own classes as soon as one can (knowing that in Java there is no risk of damaging another part of the code).
Tip: The KL Group's JProbe tool can help identify possible sources of memory leaks by showing which objects are holding on to graphs of references to other objects.
Note: Implementations of Sun's JVM prior to HotSpot used a technique called conservative garbage collection, which could introduce memory leaks of its own, beyond those caused by the programmer. To wit, as long as the application contained a 32-bit integer primitive (int) whose value coincided with the address of an object, the garbage collector would not reclaim the object. Although the likelihood was small, it wasn't zero. For this reason, and for the best performance in general, use HotSpot where possible.
About the author
Random Walk Computing is the largest Java/CORBA consulting boutique in New York, focusing on solutions for the financial enterprise. Known for their leading-edge Java expertise, Random Walk consultants publish and speak about Java in some of the most respected forums in the world.- Feedback
Resources
- The KL Group's home page
http://www.klgroup.com/ - Sun's Java HotSpot Performance Engine home page
http://java.sun.com/products/hotspot/index.html
- Related reading in JavaWorld
- "Can HotSpot jumpstart your Java applications?" Steven Brody (June 1999). A look at the HotSpot JVM, including it's garbage
collection features
http://www.javaworld.com/javaworld/jw-06-1999/jw-06-hotspot.html - "Object finalization and cleanup," Bill Venners (June 1998). Covers how to design classes for proper object cleanup
http://www.javaworld.com/jw-06-1998/jw-06-techniques.html - "Build your own ObjectPool in Java to boost app speed," Thomas E. Davis (June 1998). Explains how to use object pooling to
share instantiated objects, improving speed while reducing memory requirements
http://www.javaworld.com/jw-06-1998/jw-06-object-pool.html - "Not using garbage collection," Chuck McManis (September 1996). Discusses how to minimize heap thrashing in your Java programs
http://www.javaworld.com/javaworld/jw-09-1996/jw-09-indepth.html - "Under the hoodJava's garbage-collected heap," Bill Venners (August 1996)provides an introduction to garbage collection
http://www.javaworld.com/javaworld/jw-08-1996/jw-08-gc.html
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Helpful piece of information!!!By Anonymous on November 19, 2009, 9:36 pmHelpful piece of information!!!
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