Why I cannot update the table?

I have installed Oracle8i in Windows 2000. I can use update table_name set fieldname=value to update a record in sqlplus.
Hoever, when I use JDBC (thin driver and OCI driver) and SQLJ, the program will block after calling uppdate table_name set fieldname=value. I need to press Ctrl-C to terminate the program.

Why I cannot update record in database through Java program?

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