java - combo box that has district names as items and whose value are displayed in a textfield interms of the districts' code -

i want text field display codes of districts corresponding district name selected user combo box in same interface returning codes first , last districts. can do? codes , names in same database. sample code used below:

 private void stationspopupmenuwillbecomeinvisible(javax.swing.event.popupmenuevent evt) {                                                               // todo add handling code here:    string  connectionurl = "jdbc:mysql://localhost:3306/crime_records";   string dbuser = "root";   string dbpwd = "cfm";   connection conn;   resultset rs;    try{      string tmp = (string)stations.getselecteditem();      string sql ="select * station_codes station_name = ?";      preparedstatement pst;           class.forname("com.mysql.jdbc.driver");       conn= (connection) drivermanager.getconnection(connectionurl, dbuser,dbpwd);      pst=(preparedstatement) conn.preparestatement(sql);       pst.setstring(1, tmp);      rs=pst.executequery();       if(rs.next()){        string n = rs.getstring("code");        code.settext(n);      }                        }   catch(exception e)   {       joptionpane.showmessagedialog(null,e);   } }        

it difficult find cause of problem , analyze why application returning codes first , last districts. hovercraft full of eels remarked, seems relevant part of code missing?

for user interface part of question, consider using code example below:

import java.awt.borderlayout;  import javax.swing.jcombobox; import javax.swing.jframe; import javax.swing.jtextfield; import javax.swing.windowconstants;  /**  * https://stackoverflow.com/questions/29852371/  * combo-box-that-has-district-names-as-items-and-whose-value-are-displayed-in-a-te  */ public class districtsgui {     private static final district[] districts = {             new district("name 1", "code 1"), new district("name 2", "code 2"),             new district("name 3", "code 3"), new district("name 4", "code 4"),             new district("name 5", "code 5"), new district("name 6", "code 6")     };      public static void main(final string[] args) {         new districtsgui().getstarted();     }      private void getstarted() {         final jframe frame = new jframe("stack overflow: districts");         frame.setbounds(100, 100, 800, 600);         frame.setdefaultcloseoperation(windowconstants.exit_on_close);          final jcombobox<district> districtcombobox = new jcombobox<>(districts);         final jtextfield districttextfield = new jtextfield("");          frame.getcontentpane().add(districtcombobox, borderlayout.north);         frame.getcontentpane().add(districttextfield, borderlayout.center);          districtcombobox.addactionlistener(e -> {             final district selecteddistrict                 = (district) districtcombobox.getselecteditem();             districttextfield.settext(selecteddistrict.getcode());         });          // select first item in combo box explicitly,         // initialize text field too.         districtcombobox.setselectedindex(0);          frame.setvisible(true);     } } 

the district class this:

public class district {     private final string name;     private final string code;      public district(string name, string code) {         this.name = name;         this.code = code;     }      public string getname() {         return name;     }      public string getcode() {         return code;     }      @override     public string tostring() {         return name;     } }