When does System.gc() do something?

Question

I know that garbage collection is automated in Java. But I understood that if you call System.gc() in your code that the JVM may or may not decide to perform ga

Answer 1

I can't think of a specific example when it is good to run explicit GC.

In general, running explicit GC can actually cause more harm than good, because an explicit gc will trigger a full collection, which takes significantly longer as it goes through every object. If this explicit gc ends up being called repeatedly it could easily lead to a slow application as a lot of time is spent running full GCs.

Alternatively if going over the heap with a heap analyzer and you suspect a library component to be calling explicit GC's you can turn it off adding: gc=-XX:+DisableExplicitGC to the JVM parameters.