With a little more information I can get a more helpful answer.
If you are using MySQL:
stmt = conn.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
java.sql.ResultSet.CONCUR_READ_ONLY);
stmt.setFetchSize(Integer.MIN_VALUE);
from http://www.oracle.com/technology/tech/java/sqlj_jdbc/htdocs/jdbc_faq.html:
java.util.Properties info = new java.util.Properties();
info.put ("user", "scott");
info.put ("password","tiger");
info.put ("defaultRowPrefetch","15");
getConnection ("jdbc:oracle:oci:@",info);