Hi,
First I would like to thank you all for your efforts. Really JIProlog is a powerful IDE for Prolog and a good Java-Prolog interpreter. 
Kindly I have a problem in creating a custom built-in predicate, my problem appears when I am trying to pass a value of type String from Prolog to Java.
I had implemented the example (RandomNumberGen3) in p.65 in reference manual and it worked well with no problems because I passed a numbers but when I had created another custom predicate and I tried to pass a String to it, an error always appear.
Error:
JIP:- getvalue('apple','banana','n',X)
error(runtime_error('Unexpected call'), context(xcall('.'(74, '.'(87, '.'(111, '.'(114, []))))), '.'(apple, '.'(banana, '.'(n, '.'(_4944546, []))))), file(undefined, 0)))
Unexpected call
Waiting your help.
Thanks in advance.