It's hard to say what should be changed because mIndex is not otherwise used. If I had to guess, it should be used to select the question initially, with a default value of 0 if none has been saved before.
If an unpacking step is acceptable I don't understand the point of a fat jar. You can simply create a zip with all jar files, unpack it, and double click the main jar file. The others can be referenced via that jar file's manifest.