¿When running command line launcher:
$ java -Xmx1000g -classpath "$ANT_HOME/lib/ant-launcher.jar" "-Dant.home=$ANT_HOME" org.apache.tools.ant.launch.Launcher

We got the detailed message:
Invalid maximum heap size: -Xmx1000g
The specified size exceeds the maximum representable size.
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

However, with the same command, javaw.exe just give a generic error dialog and just exit, without details about what causing the error.

This affect both developer and end-user of javaws tool, which internally invoke javaw.
Please see also CR 6684582, which was closed without a actual fix committed or fix without general solution?