What exactly is the main thread?

please consider this code:
public class Foo {
    public static void main(String[] args) {
          ((Foo) Thread.currentThread()).bar(); // <--- error. see stack trace below.
    public void bar() {
        System.out.println("--bar()--");
}stack trace: Exception in thread "main" java.lang.ClassCastException: java.lang.Thread cannot be cast to testingarea.Foo
So what does this say about the main entry thread? is it an instance of "Foo"? or an instance of java.lang.Thread? If an instance of "Foo" why can't I invoke an instance method on the return value of "Thread.currentThread()"? If the main thread is an instance of java.lang.Thread, then where is the:
"public void run();" method?
While I can't think of any practical usage of this knowledge yet, but I'd still like to know. Thanks.
Edited by: outekko on Mar 17, 2010 6:38 PM

joshg_75 wrote:
You should always refer to the javadoc for infomation of a method and its usage. In this case, refer to the javadoc of the Thread class.
http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Thread.html
I suggest you also read up on usage of threads.Can you please share a little of your expertise in threads?
Remember this is the "New To Java" forum, and I am just a beginner as you discovered. Any help from experts would be embraced. Before you became a thread expert, you must have started somewhere. I don't need immediate assistance, but whenever you get the time, why not cut/paste this into your IDE and take a look.
public class Main {
static ObjectOutputStream oos;
static ObjectInputStream ois;
public static void main(String[] args) {
    try {
      PipedInputStream pin = new PipedInputStream();
      PipedOutputStream pout = new PipedOutputStream(pin);
      oos = new ObjectOutputStream(pout);
      ois = new ObjectInputStream(pin);
      new OutThread().start();
      for(;;) {
        Thread t = (Thread) ois.readObject();
        t.start();
    } catch (Exception e) { e.printStackTrace(); }
      public static class OutThread extends Thread implements Serializable {
        public void run() {
          System.out.println("OutThread::run--> id# " + this.getId());
          try { Thread.sleep(1030); } catch (InterruptedException e) { }
          try {
            oos.writeObject(this);
            hangAround();
          } catch (Exception e) { e.printStackTrace(); }
        public void hangAround() {
          for (;;) {
            System.out.println("_____waiting around... id# " + this.getId());
            try { Thread.sleep(5030); } catch (InterruptedException e) { }
}Not only do I appear to serialize instances of threads, the threads are actually running . So, does a live thread have private, non-transient, "state" that needs to be persisted? If so, why does serialization work? If not, why not write in the API that java.lang.Thread implements Serializable ? Whatever understanding (if any) I had of threads has melted to nothing. I am struggling with your field of expertise; please help me get back on track. Any assistance embraced.
ps. don't offer friendly criticism by scolding my design of serialized threads. My only goal is to see if I can do it (and learn something along the way).

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