4

I am writing a Java program and at some point during execution I want to change the JVM settings (decrease the heap) and after a while increase it again. Is it possible with Java?

Whymarrh
  • 13,139
  • 14
  • 57
  • 108
salvador
  • 1,079
  • 3
  • 14
  • 28

2 Answers2

1

Long story short: you can't. Heap size is fixed once you are running it, and there's no way to modify it from the code.

Silverlord
  • 88
  • 7
1

I do not think this is possible, but you could of course control the heap with -Xmx or -Xms. You can also play with : -XX:MaxHeapFreeRatio : this is the maximum percentage (70 by default if I am no mistaken) of the heap that is free before GC will shrink it.

Giving a small -Xms will make the heap grow (if needed and will involve a full GC) and shrink back is possible also.

Generally people try to avoid as much as possible this shrinking and growing because it involves a gull GC aka stop-the-world events that will slow you down.

Eugene
  • 117,005
  • 15
  • 201
  • 306