question: public boolean addOwner ( Principal caller , Principal owner ) throws NotOwnerException { if ( ! ownerList . contains ( caller ) ) throw new NotOwnerException ( ) ; if ( ownerList . contains ( owner ) ) { return false ; } else { ownerList . addElement ( owner ) ; return true ; } }
target:  Adds an owner. Only owners can modify ACL contents. The caller principal must be an owner of the ACL in order to invoke this method. That is, only an owner can add another owner. The initial owner is configured at ACL construction time.