Question

What is the best way to wait for an event/update. For example, I am waiting for this data structure to be updated before doing something. Implementing it inside a loop is not the best way since it consumes much CPU time like:

while (true) {
   // keep checking the data structure
   // if data structure is updated
   //    break;
}
// do something here

What’s a simple but efficient way to implement something like this in Java?

Answer 1

wait-notifyAll is more efficient way than loop.

Standard idiom for wait():

synchronized (obj) {
    while(condition not hold) 
        obj.wait();
}

But it’s primitive way to control threads, you’d better use classes in java.util.concurrent package. Moreover, I will choose Chris Dail’s answer if I meet such problem.