Optimizing Java

Foreword

How do you define performance?

Most developers, when asked about the performance of their application, will assume some measure of speed is requested. Something like transactions per second, or gigabytes of data processed…getting a lot of work done in the shortest amount of time possible. If you’re an application architect, you may measure performance in broader metrics. You may be more concerned about resource utilization than straight-line execution. You might pay more attention to the performance of connections between services than of the services themselves. If you make business decisions for your company, application performance will probably not be measured in time as often as it is measured in dollars. You may argue with developers and architects about resource allocation, weighing the cost of devops against the time it takes to do the company’s work.

And regardless of which role you identify with, all these metrics are important.

I started out developing Java applications in 1996. I had just moved from my first job writing AppleScript CGIs for the University of Minnesota’s business school to maintaining server-side Perl applications for the web development team. Java was very new then—the first stable version, 1.0.2, was released earlier that year—and I was tasked with finding something useful to build.

Back in those days, the best way to get performance out of a Java application was to write it in some other language. This was before Java had a Just-in-Time ...