java - MySql expected output not coming -

so have program reads serial input com port , places in mysql database named asset.

code:

import java.io.*; import java.util.*; import gnu.io.*; import java.sql.*;  public class simpleread implements runnable, serialporteventlistener { static commportidentifier portid; static enumeration portlist; static connection con=null; static string url = "jdbc:mysql://localhost:3306/track"; static string uid="root"; static string pwd="root";  inputstream inputstream; serialport serialport; thread readthread;  public static void main(string[] args) { portlist = commportidentifier.getportidentifiers();  while (portlist.hasmoreelements()) {     portid = (commportidentifier) portlist.nextelement();     if (portid.getporttype() == commportidentifier.port_serial) {          if (portid.getname().equals("com1")) {     //                if (portid.getname().equals("/dev/term/a")) {             simpleread reader = new simpleread();                 try                 {                      class.forname("com.mysql.jdbc.driver");                     con =     drivermanager.getconnection(url,uid,pwd);                 }                 catch(exception s){                     system.out.println(s);                     }      } } }  }  public simpleread() {  try {      serialport = (serialport) portid.open("simplereadapp", 2000);  } catch (portinuseexception e) {system.out.println(e);}  try {     inputstream = serialport.getinputstream();  } catch (ioexception e) {system.out.println(e);}  try {     serialport.addeventlistener(this);  } catch (toomanylistenersexception e) {system.out.println(e);}  serialport.notifyondataavailable(true);  try {     serialport.setserialportparams(9600,         serialport.databits_8,         serialport.stopbits_1,         serialport.parity_none);   } catch (unsupportedcommoperationexception e) {system.out.println(e);}   readthread = new thread(this);   readthread.start();   }  public void run() { try {     thread.sleep(20000); } catch (interruptedexception e) {system.out.println(e);} }  public void serialevent(serialportevent event) { switch(event.geteventtype()) { case serialportevent.bi: case serialportevent.oe: case serialportevent.fe: case serialportevent.pe: case serialportevent.cd: case serialportevent.cts: case serialportevent.dsr: case serialportevent.ri: case serialportevent.output_buffer_empty:     break; case serialportevent.data_available:     byte[] readbuffer = new byte[20];      try {         while (inputstream.available() > 0) {             int numbytes = inputstream.read(readbuffer);         }         system.out.print(new string(readbuffer));     } catch (ioexception e) {system.out.println(e);}      statement st=null;     try{         st=con.createstatement();      }     catch(exception ex)     {         system.out.println(ex);     }      try{         string idd = new string(readbuffer);         string query = "insert asset (id) values(?)";         preparedstatement pstm = con.preparestatement(query);         pstm.setstring(1, idd);         pstm.executeupdate();         pstm.close();         con.close();          //st.executeupdate("insert asset(id) values('"+idd+"'");         //con.close();     }     catch(exception ex){         system.out.println(ex);                 }                 break;     } } } 

so whenever data recieved com port, entry created above code in mysql table.

the expected entry should :

what actual output :

what happens 1 input com port creating 2 entries table 1 serial input , timestamp , 1 timestamp.

what want achieve 1 entry per com input. expected image.

check id before inserting database -

    string idd = new string(readbuffer);     if(!idd.equals("") || !idd.equals(null)){        string query = "insert asset (id) values(?)";        preparedstatement pstm = con.preparestatement(query);        pstm.setstring(1, idd);        pstm.executeupdate();        pstm.close();        con.close();     }