Java App: Maximum Useful RAM

I’m using a Java app I found, and it appears that it’s expecting smaller data sets than I want to use.
In particular, it’s designed to allow a bookstore to shop for used books.
It appears that the author expected a store to shop for a few hundred items at a time, while I’m wishing to shop for several thousand items.
It appears I’m just running out of RAM while using the app, although it’s possible the program also has some problems due to the actual code.

Well, here’s the question:
How much RAM can I buy for my PC before a java app can no longer usefully address it?
The app won’t be useful without you having files supplied by a used book wholesaler, but if you want to take a peek at it you can look at:

Thanks in advance!

Java can use as much memory as the OS will allow it to have, although you have to tell the Java runtime to use extra memory.

Do you mean the app tells it, or do you mean the “JRE” tells it?

To invoke an app, you say java -jar <some jarfile>. You can pass additional arguments to java – one of them is the maximum amount of memory it will use. I’ve looked it up; the argument is -Xmx. For example, to tell java to use a max of 1GB of memory, use:

java -Xmx 1G -jar <some jarfile>

The M (for MB) suffix is also accepted.

Looks like this is bundled in with a JNLP…