how to make parent thread wait for child thread to complete

[yogeshseth]

Hi,
From my main thread, i am spawning few child threads.

AnObject obj = new AnObject();
for(int i =0;i<someInt;i++) {
          ATarget aTarget = new ATarget(obj);
          Thread t = new Thread(aTarget);
          t.start();
}
 
obj.waitForAllThreadsAndDoSomething();

In the last method call, i want to do something which requires all the threads to be finished processing. One brute force approach is to implement the method waitForAllThreadsAndDoSomething() in the following manner:

while(true) {
    if(aCounter >= childrenThreadsCount) {
       //do something
    }
}

but this is too ugly and memory consuming.

can anyone suggest a cleaner approach by using methods in thread class like: wait(), notify(), yeild() ?

cheers

[ractoc]

Dirst of all, you do not want to go create objects inside a loop.
Second, you need to have the Thread instance availlable outside of the loop to be able to call any methods on it.

AnObject obj = new AnObject();
for(int i =0;i<someInt;i++) {
          ATarget aTarget = new ATarget(obj);
          Thread t = new Thread(aTarget);
          t.start();
}
 
obj.waitForAllThreadsAndDoSomething();

should be:

AnObject obj = new AnObject();
Thread[] ta = new Thread[someInt];
for(int i =0;i<someInt;i++) {
          ATarget aTarget = new ATarget(obj);
          Thread t = new Thread(aTarget);
          t.start();
          ta[i]=t;
}
// now we can access the  actual threads:
for(int i =0;i<someInt;i++) {
          ta[i].join();
}

the join method makes the parent thread wait on the child threads.


In the last method call, i want to do something which requires all the threads to be finished processing. One brute force approach is to implement the method waitForAllThreadsAndDoSomething() in the following manner:

while(true) {
    if(aCounter >= childrenThreadsCount) {
       //do something
    }
}

but this is too ugly and memory consuming.

can anyone suggest a cleaner approach by using methods in thread class like: wait(), notify(), yeild() ?

cheers[/QUOTE]