Thread.join

[Vishal Arora]

Please let me know whethere it is tru or not:
A timeout of of zero will allow Thread.join to wait forever if necessary.

If it is true then how.

[marc weber]

According to the API, "A timeout of 0 means to wait forever."

[Sergei Iakhnin]

It is true. Not sure what you mean by "how". What specifically about how it's possible interests you?

[Joe Sondow]

Here's how. The code for Thread.join(long millis) is as follows:

public final synchronized void join(long millis) 
    throws InterruptedException {
long base = System.currentTimeMillis();
long now = 0;
 
if (millis < 0) {
            throw new IllegalArgumentException("timeout value is negative");
}
 
if (millis == 0) {
    while (isAlive()) {
wait(0);
    }
} else {
    while (isAlive()) {
long delay = millis - now;
if (delay <= 0) {
    break;
}
wait(delay);
now = System.currentTimeMillis() - base;
    }
}
    }

[shyam ramineni]

Hi All,

From the code I understand that if we call t2.join(0) in thread t1, then, t1 will wait forever till t2 completes.
t1 will start if thread t2 has finished.

am I right.

Shyam Ramineni

[Joe Sondow]

Originally posted by shyam ramineni:
Hi All,

From the code I understand that if we call t2.join(0) in thread t1, then, t1 will wait forever till t2 completes.
t1 will start if thread t2 has finished.

am I right.

Shyam Ramineni

Almost right. Your first sentence is correct. t1 will wait, potentially forever, until t2 completes. Your second sentence is not quite right, but it's close. t1 won't necessarily start up again if t2 has finished, but t1 will become runnable when t2 finishes, so the thread scheduler can then resume the execution of t1 when the scheduler chooses to do so.