ConcurrentHashMap wait for key possible?

Question

i have multithread communication. 1 Thread is dispatching datas to other threads.

Main thread is pushing data:

Main Thread: ConcurrentHashMap map = Glob

Answer 1

You can use BlockingQueue if you allowed to change your implementation, or use a wait/notify technique to wait and run when occupy.

String value = null;
while(true) {
    if((value = map.get(1)) != null) { // VARY IMPORTANT to use get and !=
        // work with value 
    } else {
        map.wait(); // should be in a synchronized block.
    }
}

and for producer:

String value = "Test";
map.put(1,value);
map.notifyAll(); // or notify().