How is the default Java heap size determined?

Question

If I omit the -Xmxn option from the Java command line then a default value will be used. According to Java documentation

"the default value is chosen at runtime based on system configuration"

What system configuration settings influence the default value?

Answer 1

On Windows, you can apply the subsequent command to find out the defaults on the system wherever your applications run.

java -XX:+PrintFlagsFinal -version | findstr HeapSize

Watch for the opportunities MaxHeapSize (for -Xmx) and InitialHeapSize for -Xms.

On a Unix/Linux system, you can make

java -XX:+PrintFlagsFinal -version | grep HeapSize

I think the resulting product is in bytes.