Out of memory prblem with threads

Question

class B implements Runnable
If in class A I do
while(true)
B b = new B();
b.run()
It can create 10000 instances of B, with no problem. Since b is in the scope of the while, the old instance is cleaned up by the garbage collector every loop.
But if I do:
while(true)
B b = new B();
Thread t = new Thread(b);
t.start();
after around 400 loops I get out of memory.
If I add a finalize() method to B , I see it never called until the out of memory happens. This means the instances of the thread are not cleaned by the garbage collector.
Does anyone know why this is happening and what I can do to solve it?

Answer 1

An object is collectable if no path extists to it. One set of path is from the stack frames of all live threads. As each thread effectively holds a reference to itself, it is not suprising that the Thread instances aren't collected until the threads all end. Your rapid loop is obviously creating threads faster than they can complete (you don't show us what they are doing) so running out of memory is guaranteed.