Thanks for all these suggestions. I tried to use Saxon but ran into typical problems. I have not found an endorsed dir anywhere, and after looking at about a dozen webpages, I am ready to give up and ask: how to put it into the endorsed dir? Also very usable: how to make this one program use the Saxon classes? 
I did download files saxon8.jar and saxon9he.jar . 

BTW I did correct my usage of java command line: correct is 
java -Xmx1152m MyClass MyArguments 
I was getting the default heap size, and an extra argument to my class, by using 
java MyClass MyArguments -Xmx4096m 
I did find that 1152m is the upper limit on this system, either inside Eclipse or from the command line, even after a fresh boot.