For theory backgroud:
http://download-west.oracle.com/docs/cd/B10501_01/java.920/a96654/oralob.htm#1000888
Step1. Insert empty_clob() into the Clob column of Oracle
Step2. Set autocommit to false
Step3. Select Clob as oracle.sql.CLOB from database
Step4. Insert String into Clob
Step5. Commit
Example:
I use Oracle 9i and Java 1.4, JDBC 9i, friend also test above code on Oracle 8i with Java 1.2, hope this helps.