Thread: How to solve NullPointerException in runtime?

only this problem:

/*
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 * and open the template in the editor.
 */
 
package serversynchro;
 
import java.util.concurrent.atomic.AtomicInteger;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.util.logging.Level;
import java.util.logging.Logger;
 
/**
 *
 * @author Lolek
 */
 
public class Main {
 
    /**
     * @param args the command line arguments
     */
 
    public static void main(String[] args) {
        try {
            byte[] ip ={Network.ip(127),Network.ip(0),Network.ip(0),Network.ip(1)};
            InetAddress klient1 = InetAddress.getByAddress(ip);
            byte[] ip2 ={Network.ip(127),Network.ip(0),Network.ip(0),Network.ip(1)};
            InetAddress klient2 = InetAddress.getByAddress(ip2);
 
            Port1 nPort1 = new Port1();
            Port2 nPort2 = new Port2();
 
 
            Preposilani1 nPrepos1 = new Preposilani1();
            Preposilani2 nPrepos2 = new Preposilani2();
 
            Vlakno1 serverSocket1 = new Vlakno1();
            Vlakno2 serverSocket2 = new Vlakno2();
 
            System.out.println(nPort1.getData());
 
            serverSocket2.vlak2.start();
            serverSocket1.vlak1.start();
 
            Thread.sleep(60000);
 
            while(true)
            {
                DatagramPacket odesilanyPaket2 = new DatagramPacket(nPrepos2.getData(), nPrepos2.getData().length, klient1, nPort1.getData());
                serverSocket2.server2.send(odesilanyPaket2);
 
                DatagramPacket odesilanyPaket1 = new DatagramPacket(nPrepos1.getData(), nPrepos1.getData().length, klient2, nPort2.getData());
                serverSocket1.server1.send(odesilanyPaket1);
            }
        }             
        catch (InterruptedException ex) {
            Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
        }        catch (IOException ex) {
            Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
        }
 
         }    
 
    }
 
 
 
class Vlakno2 implements Runnable
{ 
    private Port2 cisloPort2;
    private Preposilani2 prepos2;
    volatile DatagramSocket server2;
    Thread vlak2;
    Vlakno2()
    {
    vlak2 = new Thread(this,"Vlakno 2");
    }
    public void run ()
    {        
        try 
        {
            server2 = new DatagramSocket(4000);
            byte[] prijata = new byte[256];
            byte[] odeslana2 = new byte[256];
            byte[] ip ={Network.ip(192),Network.ip(168),Network.ip(1),Network.ip(101)};
            int port2=0;
            while(true)
            {
             DatagramPacket prijatyPaket2 = new DatagramPacket(prijata,prijata.length);
             server2.receive(prijatyPaket2);
             port2 = prijatyPaket2.getPort();
             System.out.println(port2);
             cisloPort2.setData(port2);
             String prijaty = new String(prijatyPaket2.getData());
             System.out.println("Od 2. klienta:"+prijaty);
             odeslana2 = prijaty.getBytes();
             prepos2.setData(odeslana2);
 
            }            
        } 
        catch (IOException ex) 
        {
            Logger.getLogger(Vlakno2.class.getName()).log(Level.SEVERE, null, ex);
        }    
    }
}
 
class Vlakno1 implements Runnable
{ 
    private Port1 cisloPort1;
    private Preposilani1 prepos1;
    volatile DatagramSocket server1;
 
    Thread vlak1;
 
    Vlakno1()
    {
         vlak1 = new Thread(this,"Vlakno 1");
    }
    public void run ()
    {  
 
 
        try 
        {
            server1 = new DatagramSocket(5000);
            byte[] prijata = new byte[256];
            byte[] odeslana1 = new byte[256];
            byte[] ip ={Network.ip(192),Network.ip(168),Network.ip(1),Network.ip(101)};
            int port1;
 
 
            while(true)
            {
             DatagramPacket prijatyPaket2 = new DatagramPacket(prijata,prijata.length);
             server1.receive(prijatyPaket2);
             port1 = prijatyPaket2.getPort();
             System.out.println(port1);
             cisloPort1.setData(port1);     
            // ipAdresa1 = prijatyPaket2.getAddress();
             String prijaty = new String(prijatyPaket2.getData());
             System.out.println("Od 1. klienta:"+prijaty);
             odeslana1 = prijaty.getBytes();
             prepos1.setData(odeslana1);                        
            }            
        } 
        catch (IOException ex) 
        {
            Logger.getLogger(Vlakno1.class.getName()).log(Level.SEVERE, null, ex);
        }    
    }
}
 
 
class Port1 {
    private AtomicInteger portt1 = new AtomicInteger();
    public synchronized void setData(int portt1){
        this.portt1.incrementAndGet();  
 
    }
    public synchronized int getData(){
        return this.portt1.get();
    }
}
class Port2 {
    private AtomicInteger portt2 = new AtomicInteger();
    public synchronized void setData(int portt2){
         this.portt2.incrementAndGet();  
 
    }
    public synchronized int getData(){
        return this.portt2.get();
    }
}
class Preposilani1 {
    private byte[] odeslat1 = new byte[256];
    public synchronized void setData(byte odeslat1[]){
         this.odeslat1=odeslat1;
 
    }
    public synchronized byte[] getData(){
        return this.odeslat1;
    }
}
class Preposilani2 {
    private byte[] odeslat2 = new byte[256];
    public synchronized void setData(byte odeslat2[]){
        this.odeslat2=odeslat2;
 
    }
    public synchronized byte[] getData(){
        return this.odeslat2;
    }
}

When program start everything is OK. But when Clien send datagram. Write this stuf.

try changing

int port1;

to

int port1 = 0;

shouldn't make a difference for the error you are getting but always need to be sure.

PS Please post the server and client, that way we can complie and run both, so it will actually recreate the error for us.

Cheers,
Chris

I tried it. It same. Code client:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
 
package messenger;
 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.util.logging.Level;
import java.util.logging.Logger;
 
/**
 *
 * @author Lolek
 */
public class Main
{
 
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) 
    {
        try {
                 DatagramSocket Test = new DatagramSocket();
                 byte[] test = new byte[256];
                 String testik =""; 
                 test = testik.getBytes();
                 byte ip[] = { Network.ip(127), Network.ip(0), Network.ip(0), Network.ip(1)};
                 InetAddress adresa = InetAddress.getByAddress(ip);
                 DatagramPacket testDatagram = new DatagramPacket(test,test.length,adresa,5000);
                 Test.send(testDatagram);
                 Test.close();
 
            while (true)
            {
                try {
                        BufferedReader cteni = new BufferedReader(new InputStreamReader(System.in)); //cteni z klavesnice(vytvoreni proudu dat)
                        String ukonceni = "/q";
                        DatagramSocket klient = new DatagramSocket(); //vytvoreni klientskeho soketu
                        try {
                                  InetAddress lokalni = InetAddress.getByName("localhost"); //ziskani lokalni IP adresy
                                  byte[] poslana = new byte[256]; //vytvoreni 256 bytoveho pole pro posilana data
                                  byte[] prijata = new byte[256]; //vytvoreni 256 bytoveho pole pro prijimana data
                                  String klavesnice = cteni.readLine(); //cteni po radku a prirazeni do k
                                  poslana = klavesnice.getBytes(); //prirazani dat do poslana
                                  DatagramPacket odesilanyPaket = new DatagramPacket(poslana, poslana.length, lokalni, 5000); //zabaleni pole bajtu k odeslani +definice cilove IP adresy a portu
                                  klient.send(odesilanyPaket); //odeslani paketu
                                  DatagramPacket prijatyPaket = new DatagramPacket(prijata, prijata.length); //zaobalnei pole bajtu k prijmu
                                  klient.receive(prijatyPaket);                        //prijimani dat                        
                                  String prijataData = new String(prijatyPaket.getData()); //ulozeni dat do retezce
 
                                  if (!prijataData.isEmpty())
                                  {
                                     klient.send(testDatagram);
                                  }
                                  System.out.println("Od serveru:" + prijataData); //Vypis prijatych dat od serveru
 
                                  if (prijataData.equals(ukonceni))
                                  {
                                         System.exit(0);
                                  }
                                  klient.close();
                             } 
                        catch (IOException ex) 
                             {
                                  Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
                             }
                     }
                catch (SocketException ex) 
                     {
                         Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
                     }
            }
 
        } 
   catch (IOException ex)
        {
            Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
        } 
 
 
 
 
    }
 
}
class Network {
 
public static byte ip(int i)
{
    return (byte) ((i > 127) ? i - 256 : i);
}
}

Thanks a lot Chris and Don Carleone.

First compile server and after compile client.

Even playing with IP address etc I cannot get the erro, or any outputs. Could you print screen the output?

Printscree http://img18.imageshack.us/img18/3886/printscreenf.jpg

Well you don't even use the port1 integer you are trying to pass anyway, so one solution would be to remove it from the function call and the function prototype. Then re-run and see if you are still getting a problem

Chris

Originally Posted by JavaPF

Yes the problem is with cisloPort1.setData(port1);

port1 is null causing the NullPointerException.

Thats what I thought, so via removing the need to send port1 as an argument, since it is never used it would remove the problem. However I still cannot work out why it would do this

Hi Koren3,

The NULL pointer exception is because you never initialized these two vars: cisloPort1 and prepos1

Go to class Vlakno1 and replace the first two lines with this:

private Port1 cisloPort1 = new Port1();
private Preposilani1 prepos1 = new Preposilani1();

Thanks it solved.