Hi,
I am not sure what OS your ASE resides on or where you are executing your java application from or what version of the jconn4.jar you are using?
Try the following and see if this can clean anything up. Change your packet size to 1024 in the java connection string.
Is the java connection calling a remote server with a stored procedure?
Could it be the remote server to the ASE keeping the connection alive?
Do you see anything in the ASE log related to pci memory does this need to increased?
Thanks,
Dawn Kim