Question

What’s the proper way for a Java command line application to do background work without hogging resources? Should it use sleep() in the loop or is there a more elegant/efficient way?

Answer 1

Some heuristics:

• Don’t attempt to make scheduling decisions in your application. The operating system’s scheduler is way better than yours will be. Let it do its job.
• Don’t poll if you don’t have to. For instance, instead of sleeping n seconds, then waking up to check a non-blocked socket, block on the socket. This second strategy plays better with the operating system’s scheduler.
• Don’t use an enormous heap if you don’t have to, and try not to allocate enormous chunks of memory at one time. A thrashing application tends to have a negative effect on system performance.
• Use buffered I/O. Always. If you think you need non-buffered I/O, be absolutely sure you’re right. (You’re probably wrong.)
• Don’t spawn a lot of threads. Threads are surprisingly expensive; beyond a certain point, more threads will reduce your application’s performance profile. If you have lots of work to do concurrently, learn and use java.util.concurrent.

Of course, this is just a starter list…