How do you declare the jStringUtils library?
Is it checked in the IDE?
It must be jStringUtils not StringUtils, see below.
When you look in the C:\Program Files (x86)\Anywhere Software\B4J\libraries folder, do you see these two files:
jStringUtils.jar and jStringUtils.xml ?
These are the files for the jStringUtils library.
The strange thing is that your program is searching for stringutils.jar but the file should be jstringutils.jar.
Do have somewhere a confusion between B4J and B4A?
stringutils.jar is the B4A library file.