CODEWITHSUNDEEP
javamultithreading
Lundira
Lundira

Reputation: 179

Second thread is not reached

I am trying to start 2 threads, one for tcp and one for udp

package com.main;

import com.utility.HibernateUtil;

public class ServerStarter {

    public static void main(String[] args) {
        System.out.print("Reach 1");
        Thread tcp = new Thread(new TcpServerStarter());
        tcp.start();
        System.out.print("Reach 2");
        Thread udp = new Thread(new UdpServerStarter());
        System.out.print("Reach 3");
        HibernateUtil.buildSessionFactory();
        System.out.print("Reach 4");
    }

    public static class TcpServerStarter extends Thread{

        public TcpServerStarter(){
            new TcpServer(8500).run();
        }
    }

    public static class UdpServerStarter extends Thread{

        public UdpServerStarter(){
            new UdpServer(1000).run();
        }
    }
}

Only "reach 1" is printed. I read that this may occur if i have single core, however i have 2 cores.

Upvotes: 1

Views: 137

Answers (5)

nits.kk
nits.kk

Reputation: 5316

A thread object must be started so that the execution of the corresponding Thread can be initiated.

I see in your code below code 

System.out.print("Reach 1");
Thread tcp = new Thread(new `TcpServerStarter`());

Till now you have not yet called the tcp.start(). Till now you have created a new object of Thread.java which is OK but the main problem I feel is with the constructor of TcpServerStarter.java the code written it it prevents the flow of execution of your main method ahead.

See TcpServerStarter.java class is a Thread itself as it extends Thread.java. should override run method in your TcpServerStarter.java You Should move the code from the constructor to the run() method. Instead of creating the objects of `Thread.java modify the code as below.

Thread tcp = new `TcpServerStarter`();

Then you need to call start on the Thread object you have created. 

tcp.start()

Similarly you need to modify the code including the usage of UdpServerStarter.

Upvotes: 1

Suparna
Suparna

Reputation: 1172

Without changing too much your code, this one works. I am not sure what is your specific implementation fo TcpServer or UdpServer looks like. So implemented some dummy ones for now. I see that all the print outs print as expected.

package network;


class TcpServer implements Runnable{
    TcpServer(int port){

}

@Override
public void run() {
    for (int i=0; i < 10; i++){
        System.out.println("Thread printing:" + i + "tid:" + Thread.currentThread().getId());
        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }       
  }
}


class UdpServer implements Runnable{
    UdpServer(int port){

    }

@Override
public void run() {
    for (int i=0; i < 10; i++){
        System.out.println("Thread printing:" + i + "tid:" + Thread.currentThread().getId());
        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }       
}

}

public class ServerStarter {

public static void main(String[] args) {
    System.out.print("Reach 1");
    Thread tcp = new Thread(new TcpServerStarter());
    tcp.start();
    System.out.print("Reach 2");
    Thread udp = new Thread(new UdpServerStarter());
    System.out.print("Reach 3");
    //HibernateUtil.buildSessionFactory();
    System.out.print("Reach 4");
}

public static class TcpServerStarter extends Thread{

    public TcpServerStarter(){
        new TcpServer(8500).run();
    }
}

public static class UdpServerStarter extends Thread{

    public UdpServerStarter(){
        new UdpServer(1000).run();
    }
}

}

Upvotes: 1

Zbynek Vyskovsky - kvr000
Zbynek Vyskovsky - kvr000

Reputation: 18825

You only create udp thread but not really start it. Add this:

    udp.start();

Secondly you start the loop directly from the constructor instead of run method. Change to:

public static class TcpServerStarter implements Runnable {
    public void run(){
        new TcpServer(8500).run();
    }
 }

And similarly for the UdpServerStarter.

Upvotes: 2

shad
shad

Reputation: 124

When you call new TcpServer(8500).run(); in TcpServerStarter's constructor

It starts running the tcpServer in the MAIN thread. I'm guessing that it just serves forever and this is why it doesn't reach any of the following code.

Also what Zbynek said : you didn't start the udp thread.

Upvotes: 2

Jiri Kremser
Jiri Kremser

Reputation: 12837

Put the code into method called run() instead of calling it from the constructor (calling the run() will block the execution)

public static class TcpServerStarter extends Thread {

    @Override
    public void run() {
        new TcpServer(8500).run();
    }
}

public static class UdpServerStarter extends Thread {

    @Override
    public void run() {
        new UdpServer(1000).run();
    }
}

}

If the UdpServer and TcpServer already extends Thread or implements Runnable, you can start them directly by the start() method w/o creating the wrapper classes.

Upvotes: 1

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