Max number of threads in Java?

Question

Hi,
I am running into a bug now that I am testing my working code. Basically, my program creates a bunch of objects that talk to each other. Each object is a thread, and at a given time (there is a one object that keeps track of time) a thread may choose to message another thread. My problem is that when I create more objects, my code doesn't run to completion. For example, when I have 10 objects talking to each other, things work fine. But if I have 15, they all run for a little bit, then the program seems to just hang and not do anything.
Is there a limit as to how many threads I can have? If I was out of memory or something, I'd get an exception, right? But I don't get anything - it just seems like things "freeze up".

Answer 1

15 threads? shouldn't be a problem.
I think th emax threads allows runs in thousands..if not ten of thousands.Java process threads itself use about 600 or more threads. howevr, it could also be the underlying system restr8iction on the number of threads allow per process????
for you case: it's highly likely you run into the max # of threads.
I can only think of two reasons for your application to freeze:
1. Deadlock
if you have an object that is synchronized..than you might have run into a deadlock (race-condition)
for example:
Object A has the key for Object X , and waiting for Object Z
Object B has the key for Object Z, and waiting for Object X
as you can see..they will never gives up the lock....so you're in a dead lock.
2. Low memory resource. (Memory - Paging and Thrashing)
Each of your thread is using up the resouces (memory) and processing power.
When you reach the max or near max and needs to create more memory..the garbage collector kick in
and try to reclaim some unused memory. This can slow down your application dramatically if the garbage
collector is invoke often.
Also..paging is performed when you reach max memory..the operating system keep on paging your memory (usually happens when there's a lot of threads and not enough memory. If this happen..than it
can cause your program to becomes freeze like....remeber..each thread is given a small amount of time to
perform a task..if the time it takes to load a page for a thread is almost equals to context switch time..than
no work is really done..and your program "freeze"
solution..redesign you app to prevent thrashing.
it is likely paging is the culprit..but i would not dismiss deadlock issues.