You can write this pease of code in Application Module Impl class.
"ORDER_SEQ" is a Oracle DB Sequence.
import oracle.jbo.server.DBTransaction;
import oracle.jbo.server.SequenceImpl;
SequenceImpl orderIdSeq =
new SequenceImpl("ORDERS_SEQ", this.getDBTransaction());
orderIdSeq.getSequenceNumber();
String pOrderId =
orderIdSeq.getSequenceNumber().toString();