Does Java self-limit the number of active threads?

Question

I was hoping someone might be able to shed some light on this:
I basically have a loop which creates an instance of a class that extends Thread. This class, lets call it MyTask, may take a minute or two to run. In my run() method I system.out an ID as soon as the .start() is actioned, like this:
class MyTask extends Thread
int nMyID;
public MyTask(int vnMyID)
this.nMyID = vnMyID;
public void run()
System.out.println(this.nMyID);
// do other stuff that takes a couple of mins...
ThirdPartyAPI.dosomething();
In my loop I create an instance of MyTask and call the .start() method on it.
What I'm seeing is that rather than the ID being outputted immediately as I would expect, the IDs are being outputted over a period of time, so this to me would imply that Java is queuing the threads before starting them? I don't want it to queue the treads because the rest of MyTask is simply sat waiting for a response from a third party system. It gets through them all eventually, but it just takes a long time, and it should be quicker.
Is there anything I can do to stop it from behaving this way?
Thank you

Answer 1

BigBadBurrow wrote:
I was hoping someone might be able to shed some light on this:
I basically have a loop which creates an instance of a class that extends Thread. Unrelated to your problem, but just as a side note, that's poor design. You're almost certainly not creating a specialized kind of Thread, but rather, a task to be run in its own thread, and hence you should implement Runnable.
This class, lets call it MyTask, may take a minute or two to run. In my run() method I system.out an ID as soon as the .start() is actioned, like this:
class MyTask extends Thread
int nMyID;
public MyTask(int vnMyID)
this.nMyID = vnMyID;
public void run()
System.out.println(this.nMyID);
// do other stuff that takes a couple of mins...
ThirdPartyAPI.dosomething();
In my loop I create an instance of MyTask and call the .start() method on it.
What I'm seeing is that rather than the ID being outputted immediately as I would expect, the IDs are being outputted over a period of timeProvide an [url http://sscce.org]SSCCE
, so this to me would imply that Java is queuing the threads before starting them? Not generally, no. However, once you've started the other threads, you now have those threads running plus your main thread. If your main thread goes on to do some CPU intensive work, it might be some time before the other threads get cycles. Anytime you have more threads the CPUs/cores, there will be at least one thread that's waiting. You don't (and shouldn't need to) control which thread gets CPU when.