Java Optimization

How to optimize your Java programs so that they're faster, smaller, and more maintainable.

Topics

• Benchmarks: costs of Java operations.
• Compilers: what they can and can't do.
• Maintainability: how to make your code easier to understand.
• Resources: other places you can go for help.
• Rules: general guidelines for optimization
• Size: how to make your code smaller.
• Speed: how to make your code faster.
• Tools: software that can help you optimize Java.

What's New

March 18th, 1998

• As you've probably guessed by now, I've retired this site. After this final update of ten months' worth of email(!), I won't be making any further changes. Sorry for leaving things hanging, but I've moved on to a new job.
• Pruned all the bad links that I could find.
• Speed: more on reusing objects, avoiding expensive Java constructs and data structures, and the two types of switch.
• Linpack: why the optimized version is slower under modern JITs.
• Compilers: commercial source-code optimizer.
• Size: commercial byte-code obfuscator.
• Tools: commercial profiler.

May 26th, 1997

• Speed: another JIT, this time for HP-UX.

May 14th, 1997

• I swear it doesn't seem like two months since I last touched these pages. A PhD thesis will do that to you...
• Maintainability: four sets of coding style guidelines, avoiding gray areas of the Java spec, watching for incompatible code, and using good tools.
• Resources: links to other benchmarks, and another Java games book with optimization references.
• Size: another code obfuscator.
• Speed: list of available just-in-time compilers.
• Tools: another profile analyzer.

See also previous updates.

Some Parting Thoughts

Rules of Optimization:
Rule 1: Don't do it.
Rule 2 (for experts only): Don't do it yet.
- M.A. Jackson

"More computing sins are committed in the name of efficiency (without necessarily achieving it) than for any other single reason - including blind stupidity."
- W.A. Wulf

"We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil."
- Donald Knuth

"The best is the enemy of the good."
- Voltaire