Hack-R Hack-R - 1 year ago 58
Java Question

Java works fine in Windows but BlueJ IDE's Java fails

I have the most recent version of Java installed and it works fine in Eclipse and with other programs.

A Duke University online course wants me to download and run their flavor of BlueJ for Windows. I installed it, but it can't launch. It says:

Could not create the Java virtual machine

After ensuring that the _Java_Options environment variable sets an adequate heap I explored the BlueJ program folder. I see that in bin it has its own javaw.exe. When I try to run this I get the same error.

How can I fix this?

I'm on Windows 10 64-bit.

This IDE claims to have its own JDK and to be ready to run out of the box:


On Windows, BlueJ comes bundled with a Java Development Kit, JDK, so
only a single download is needed.

Download the Duke/Coursera specific version (choose Save instead of Run)
Double-click the downloaded install file and follow the wizard to install it in your preferred location
By default, the installer will place a shortcut to BlueJ on your desktop


I finally had the good sense to try run the .exe from the command line and pipe the results to a text file:

C:\Program Files (x86)\BlueJ>BlueJ.exe > tmp.txt

The contents of the text file are:

Error occurred during initialization of VM Could not reserve enough
space for 2097152KB object heap

So it seems that it doesn't have enough memory, but this is strange because I immediately checked Resource Monitor and my RAM usage is only 2.7 GB out of 16 GB.

To make matters more strange I just changed the
heap size to 1GB and reran the exact same command. The result was the precise same error message... it's still trying to allocate 2GB even though I scaled back the heap to 1GB...

I also set

SET JAVA_OPTS="-Xms256m -Xmx512m"

but I still get the same result.

Answer Source

At long last I got this working.

The trick was to set the initial -- not maximum and not initial and maximum -- heap size in _JAVA_OPTIONS to a very small value, which I believe is because BlueJ insists on using 32-bit Java even though 64-bit is available:


Note that the same setting in JAVA_OPTS did no good.

If you have a deeper understanding of why this is and would like to submit a better version of this answer then please do so and I'll mark your answer as the solution.