Hi,

I found that if I do not include public void main() method in class
extending Thread class, nothing can be output by it's run() method
even if .start() being called on that Thread instance. Why will that
happen ?

For example, for below program, nothing will be output as the program
being run. If I un-comment those lines, I could only see text output
by ot3, ot4 instances. Why ot1 & ot2 cannot print text out to console
?

public class OverloadThread {
 public static void main(String[] args) {
   Thread ot1 = new Thread(), ot2 = new Thread();
//    ORunnable or1 = new ORunnable(), or2 = new ORunnable();
//    Thread ot3 = new Thread(or1), ot4 = new Thread(or2);
   ot1.setName("ot1");
   ot2.setName("ot2");
//    ot3.setName("ot3");
//    ot4.setName("ot4");
   ot1.start();
   ot2.start();
//    ot3.start();
//    ot4.start();
 }
}

class Othread extends Thread {
  public void run() {
    for (int i=0; i<5; i++) {
      System.out.println("OThread."+Thread.currentThread().getName()+".run()");
      this.run("Overload");
    }
  }
  public void run(String s) {
    System.out.println("OThread."+Thread.currentThread().getName()+".run(String)");
  }
}

//class ORunnable implements Runnable {
//  public void run() {
//    for (int i=0; i<5; i++) {
//      System.out.println("ORunnable."+Thread.currentThread().getName()+".run()");
//      this.run("Overload");
//    }
//  }
//  public void run(String s) {
//    System.out.println("ORunnable."+Thread.currentThread().getName()+".run(String)");
//  }
//}

Why Thread instance class (or it's subclass) can only output text to
console when it also includes public void main() method in it's class
definition ?

class MyThread extends Thread {

 public static void main(String[] args) {
   MyThread t = new MyThread();
   t.start();
 }

 public void run() {
   System.out.println("Thread");
 }

}

Running this program produce below output

Thread