Today in the Sunlab a student ran into a problem. His program ran faster in Eclipse than on the command line. Actually, to clarify the program initially didn't run at all on the command line. Only after increasing the heap size did it run (this should give you a hint to upcoming problem).
Symptom: The program ran fine, then got slower and slower.
Reason: Getting close to the memory limit. A StackoverFlow post indicated memory was the issue. Either we were paging to disk or increasing the frequency of garbage collection. Because we previously received Heap Size errors, I was fairly certain that the delay wasn't coming from paging memory to disk. We hypothesized garbage collection.
Did we profile it? No. Ain't no body got time for that.
Did we fix it? Yes, up the jvm's heap size to 2 gigabytes.
Could be a fun profiling project in the future.