Setting up a JDBC connection to execute SQL command "TRUNCATE TABLE"

I am setting up a JDBC connection to execute the SQL command “TRUNCATE TABLE” in order to truncate some of the unnecessary log tables in TN and therefore free up some valuable space on that server. I have created this functionality, but have noticed in my test environment that it is sending me a -1 as the return value. Does anyone know what this is telling me? I have looked in the normal documentation and not found any reference to it. Any ideas would be helpful.