Mock exam thread question

[Darren Littlepage]

Hi,

I'm using Enthuware and ran across this question.

What will be the output when this program is compiled and run from the command line?

class MyClass implements Runnable
{
	int n = 0;
	public MyClass(int n){ this.n = n; }
	public static void main(String[] args)
	{
		new MyClass(2).run();
		new MyClass(1).run();
	}
	public void run()
	{
		for(int i=0; i<n; i++)
		{
			System.out.println("Hello World");
		}
	}
}

choices are:
It will print "Hello World" twice.
It'll keep printing "Hello World".
2 new threads are created by the program.
1 new thread is created by the program.
None of these.

The correct answer given is None of these.

I chose 1 new thread is created by the program.

The reason I chose this is because I thought they were being tricky and counting main as a thread.
Wouldn't it create one thread for main or would that not be the program from the command line that does that?

[Adolfo Eloy]

I think, depending on the state of the program it can have one, two or even three threads created and only one running.
Another think about it, is that if the program already run (in other words, the main thread is dead), the result will be
hello world
hello world
hello world

and there will be no threads created.

So, I think that "None of these" is the correct answer.

I hope I made myself clear.

[Richard Broersma]

It's true that a there is a tread of execution created so that this program can run. But this program does not create the initial thread; the thread is created before the program even starts to run.

[Darren Littlepage]

I get it now. So the main method is started by a thread that already existed. The program did not create it. What does create that thread? Is it the JVM when I type 'java Class'?

[ankur trapasiya]

in my point of view the right answer would be "none of these". Because thread can only be created using Thread class and here only class that implements Runnable is created and no thread is created to schedule the call to run method.

so when you create instances of the class that implements Runnable and call run method of it , it just executes like normal method call so it will print hello world 3 times and here no option regarding this answer is given. so i guess none of these is right answer.

[Adolfo Eloy]

ankur trapasiya wrote:in my point of view the right answer would be "none of these". Because thread can only be created using Thread class and here only class that implements Runnable is created and no thread is created to schedule the call to run method.

so when you create instances of the class that implements Runnable and call run method of it , it just executes like normal method call so it will print hello world 3 times and here no option regarding this answer is given. so i guess none of these is right answer.

I think you really got the point.
The run method was called instead of start.