Remove one mod at a time to determine which one stops the game from loading. However, If you’ve got many mods, this might be a bit more tricky. You can check the latest.log text document in the “ logs ...

Fix Minecraft Exit Code 6 by disabling outdated mods and updating Visual C++ and Java. Other than that, follow these suggestions.

From what I could find, Java itself never has any defined exit codes. The exit comes from whatever the java app/developer wants to do, so you'll have to talk to Pentaho and ask them what exit code ...