Synchronized issue

Question

Hi,
I have a synchronized block and Im sending a request to another application (blocking operation). So until i get response, I need to wait(), so that i wont end up consuming too much CPU. I want to wait() but i do also like to ensure that no other thread will enter this synchronized black in the mean time.
Because, i just want one thread to do this complete process and then only let the other thread come in.
I dont know how to stop other Thread acquiring lock while first thread is in waiting state.
..............Something..........
Collection col = null;
.........Some code.........
synchronized(lock)
     send(col);
     while(col == null)
          lock.wait();
     //Do further stuff     
void recieveResponse()
synchronized(lock)
     // col is populated
     lock.notify
}

Answer 1

You can always use a Semaphore or a Latch. Or better yet. Use a BlockingQueue with a Consumer-Producer pattern. Would that help?
while(col == null) {
gateLatch = new CountDownLatch(1);
gateLatch.await();
void recieveResponse() {
     synchronized(lock) {
           // col is populated
           gateLatch.countDown();
}