Java Threads - Content inside Cycles

Question

Very simple. When I use the method run like this:

 @Override
 public void run() {
     CraftRoulette.getInstance();
     while(socket==null && outputstream==null && inputstream==null) {
        System.out.println("ahah");
     }
     System.out.println("RUN");
     while(socket!=null && !socket.isClosed()) {
        System.out.println("STOP");
        System.out.println("Checking");
        checkForUpdatesOnServer();
     }
     if(socket!=null && socket.isClosed()) System.out.println("FODA-SE, MAS QUE BEM!");
}

it outputs:

 ahah
 (...)
 ahah
 RUN
 STOP
 Checking

However, if I remove the content of the first cycle:

 @Override
 public void run() {
 CraftRoulette.getInstance();
 while(socket==null && outputstream==null && inputstream==null) {
 }
 System.out.println("RUN");
 while(socket!=null && !socket.isClosed()) {
    System.out.println("STOP");
    System.out.println("Checking");
    checkForUpdatesOnServer();
 }
 if(socket!=null && socket.isClosed()) System.out.println("FODA-SE, MAS QUE BEM!");
}

It doesn't output anything. That's the only change I apply. Why does having the sysout keep the run method going and not having just kills it?

EDIT: Volatile on the socket did the job, thank you!

A bit more info: While it's doing the first cycle, I'm interacting with a framework, it's like the focus passes on to the framework only if there's not a sysout. Is this a bug? — João Mendonça, Jun 25 '18 at 04:46
Show me your client code? Need to know how you create the socket and the streams? — Ravindra Ranwala, Jun 25 '18 at 04:53
probably you need to declare your `socket` field as `volatile`, see [do we ever use volatile](https://stackoverflow.com/questions/106591). Without using `volatile` the thread might not notice that `socket` was changed from another thread. `System.out.println();` helps by being a synchronized method, requiring the thread to re-read `socket` after each call. — Thomas Kläger, Jun 25 '18 at 05:12

Java Threads - Content inside Cycles

0 Answers0