When wil the new Thread() without reference be garbage collected

Question

In the below example, new Thread() doesnt have any reference. Is it possible that it be garbage collected below it is dead ? Also without extending Thread class or implement

Answer 1

No, a Thread which has been can't be garbage collected before the underlying VM thread (whether an OS-thread or not) has finished. I'm not sure offhand whether a Thread which doesn't have any obvious references to it but hasn't been start()-ed ends up causing a leak, or whether it can be collected - the latter, I'd expect.

As for your second question - your code does extend Thread, using an anonymous inner class, here:

new Thread() {
        public void run() {
                foo();
                System.out.print(x + ", ");
        } 
}

I would personally suggest that even if you did want to use an anonymous inner class here, it's generally neater to implement Runnable:

new Thread(new Runnable() {
    public void run() {
        foo();
        System.out.print(x + ", ");
    } 
})

That way it's clear that you're just providing something to run, rather than trying to change any of the thread's core behaviour.