Printing sequence - Threads

[Sen George]

In the following code,

 
import static java.lang.System.*;

public class te_thread3 implements Runnable{

  public static void main (String[] args) {

    te_thread3 t = new te_thread3();
    Thread thread = new Thread(t);
    thread.start();
    t.doIt();
  }

  public void run() {
   out.println("\n   Thread is running.");
  }

   void doIt() {
     out.println("\n   In doIt method.");
  }
}

the output got is 'In doIt method' followed by ' Thread is running.'

I was expecting the output in reverse- ' Thread is running.' followed by ' In doIt method'. Could someone please clarify this behavior?

[Ernest Friedman-Hill]

The Thread.start() method returns pretty much immediately, but it takes some time for a thread to get going. The thread that called start() (i.e., your main thread) keeps running while the newly-created thread gets ready to go. By the time that new thread starts actually running Java code, the original thread will have executed many instructions.

So the main thread here calls start(), then immediately calls doIt(), which prints a message. All the while, the new thread is being initialized. Finally, some time after doit() is called, the new thread starts to execute your code.