public class OptionList {

private Connection conn;
private List<String> type_list = new ArrayList<>();
private List<String> partid_list = new ArrayList<>();

public OptionList() {
    //conn = null;
    //type_list = null;
    //partid_list = null;
}

public void listin_db() throws Exception, SQLException {
    JDBC ora = new JDBC();

    //1. open/get connection
    ora.openConnection();

    conn = ora.getConn();

    //2. Execute query
    String stmnt = " select distinct PARTID, NAME "
            + " from INVENTORY tblA "
            + " inner join( "
            + " select distinct part_no "
            + " from Status )tblB on tblA.Partid = tblB.part_no ";
    Statement statement = conn.createStatement();
    ResultSet rs = statement.executeQuery(stmnt);

    while (rs.next()) {
        type_list.add((String) rs.getString("NAME"));
        partid_list.add((String) rs.getString("PARTID"));
    }

    conn.close();
    statement.close();
    ora.closeConnection();

}

public List<String> getpartid_List() {
    return partid_list;
}

public List<String> getType_List() {
    return type_list;
}

public String test() {
    return "HelooWourldd!";
}