Hello Theera,
Since no one is really answering you, I'll try my hand at it. I also used exactly this library under B4A for a long time and loved it, because it ports familiar BASIC terms to B4A (left, right, mid). Unfortunately, this library did not run under B4J.
I have not yet been able to look at your work due to time constraints. But: There are built-in string functions in both B4A and B4J that work similarly and are well documented...
Imagine, you have a given string named MYSTRING, then try this in the IDE:
MYSTRING.Substring(.........................)
MYSTRING.Substring2(........................)
Follow the description for setting the pointers. It is a little bit different, but very similar when it comes to basic stringoperations.
I was able to remove Magret's stringfunctions completely. As good as it is, it is better to work with the built-in functions already available. My opinion.
Sure, there are some nice features within Magret's library (I think a low-level encryption and such things). But nowadays this library is like a 5th wheel on a car. Not necessary IMHO.
This is only a friendly advice I want to give. Not meant in a bad way. Many roads lead to rome...