java.lang.OutOfMemoryError: Java heap space Error in JVM

 Heap size is larger than your computer's physical memory. For example,

java -Xmx2g BigAppError occurred during initialization of VMCould not reserve enough space for object heapCould not create the Java virtual machine.
The fix is to make it lower than the physical memory: java -Xmx1g BigApp


Incorrectly use mb as the unit, where m or M should be used instead.

java -Xms256mb -Xmx256mb BigAppInvalid initial heap size: -Xms256mbCould not create the Java virtual machine.
The heap size is larger than JVM thinks you would ever need. For example,

java -Xmx256g BigAppInvalid maximum heap size: -Xmx256gThe specified size exceeds the maximum representable size.Could not create the Java virtual machine.
The fix is to lower it to a reasonable value: java -Xmx256m BigApp

The value is not expressed in whole number. For example,

java -Xmx0.9g BigAppInvalid maximum heap size: -Xmx0.9gCould not create the Java virtual machine.
The correct command should be java -Xmx928m BigApp