Can we only start() a thread?

[Mark Lau]

I think that we can also directly invoke the run method of the thread like so:
myThread.run();
After all, the start method also simply calls run(), right?
But look at this. This problem is from www.javacertificate.com

Which of the following statements are true? [Check all correct answers]
1 A thread is a different program.
2 A thread can share data with other threads.
3 A thread is started by calling the start method.
4 A thread is started by calling the run method.

javacertificate says only 2 and 3 are correct. I think 2 and 3 and 4 are all correct.
This is what javacertificate.com says:

The only correct way to start a thread is calling the start method of the Thread class.

Do you people agree?

[Thomas Paul]

Why do you think that the start() method only executes the run() method? Did you actually take a look at the ocde that the start() method invokes?
Here is the code:
public synchronized native void start();
So there is obviously something else going on than just executing the run() method. In fact, there is a lot more going on.
If you just run the run() method it does not create a separate thread. Only when you run the start() method does it create a separate thread.

[Mark Lau]

OK, OK, I gotcha. I was suspecting, though.
So javacertificate is actually right, right?

[Thomas Paul]

Yes, the proper way to start a thread is with the start() method.

[Marlene Miller]

class Test extends Thread {
   public void run() {
      System.out.println(Thread.currentThread().getName());
   }
   public static void main(String[] args) {
      Test t = new Test();
      t.run();
      t.start();
   }
}
main
Thread-1