Restarting dead threads

[DC200]

I'm trying to figure out a way of keeping my threads alive in my application. I've got a main method that keeps an ArrayList of all threads it has started, each of which must remain alive for however long the entire application is running. These threads usually only die when they encounter an exception (handled or unhandled).

Right now, I'm keeping them alive by having the main method iterate over its ArrayList of threads and invoking their isAlive() method once every second. If it returns false, it simply instantiates a new identical thread and replaces the dead one with it.

Though this seems to be working perfectly, this doesn't really strike me as a good solution to this problem. I'm wasting CPU time by iterating over all those threads. What else can I do besides this?

[berkeleybross]

I would prevent them from dying in the first place.
What causes them to die?

A simple approach would be to use a while loop like so:

while (true) {
    // main logic
}

[DC200]

Yes, but sometimes it's necessary to restart the threads manually due to the nature of the application.

How can the main thread find out when a thread has completed execution so it can instantiate another thread to replace it?

[Kapil Viren Ahuja]

It looks to me that you are trying do something similar to Thread Pool. I will recommend you read up on Java Concurrent package. It has most of the functionality built in. By design, once a thread is created and allocated a task, we should let me finish and not try to bring it alive. If a new task has come up, we should allocate a new thread to it.

Alternatively, you can choose not to let threads die, but return to the pool and re-use those. Java concurrent package will allow you to do either effectively and with getting away with writing lots of complicated code.