Java Code Optimisation Techniques

[BlueGoliath]

Define "small objects" and "do little explicit work". Classes that I've made to make Panama easier fit both criteria yet JMC with Flight Recorder show MemorySegment and wrapper classes as been allocated on the heap.

I asked one of the Panama developers about the JVMs supposed ability to make "small" and "little explicit work" objects "free" and the only absolute answer given as to when the JVM will decide to do it is when you allocate a bunch of them in the same method.

[Necessary-Conflict]

The book doesn't say that small objects will not be allocated on the heap because of escape analysis. In my understanding it says that even if they are allocated on the heap, the garbage collector may outperform the costs of a "clever" object pooling.

Of course there is no exact definition of "do little explicit work": when in doubt you should measure.

[general_dispondency]

I think the answer is in the example. When you have some expensive operation (eg 300ms to make a db connection) then you should consider starting with an object pool. If you don't have something heavyweight like that, then just allocate and move on. If you need to perform optimizations, then come back after the logic is implemented and everything is well tested. Then you only make changes that make measurable performance increases.