There are a number of free options as well if you're comfy rolling your own (or using Intuit test apps).
If you download the QuickBooks SDK, it includes examples of sending QuickBooks XML documents which instruct QuickBooks to add customers, add transactions, etc. etc. etc. The examples could easily be extended to allow you to copy/paste in an XML document or load an XML document from disk.
You could then build the actual XML files in Java. If you wanted to get really fancy, use JAXB (or an equivalent XSD to Class generator) to generate Java classes from the included .XSD documents, and be able to do things like: InvoiceAdd inv = new InvoiceAdd();
There's documentation about the XML format included in the QuickBooks SDK. You can also find some QuickBooks XML examples on our QuickBooks integration wiki.