https://leetcode.com/discuss/interview-question/1857832/Rubrik-or-Phone-Screen

ClientWrapper

public class ClientWrapper {
    int connectionState, requestingThreads; //-1 null, 1 init done, 2 closed
    Lock lock;
    Condition awaitRequest, awaitClose;

    ClientWrapper2(){
        //constructor
        connectionState = -1;
        requestingThreads = 0;
        lock = new ReentrantLock();
        awaitRequest = lock.newCondition();
        awaitClose = lock.newCondition();
    }

    void init(){
        lock.lock();
        try {
            if (connectionState != -1)
                return;

            connectionState = 1;
            awaitClose.signalAll();
            awaitRequest.signalAll();
        }
        catch(Exception e){}
        finally{ lock.unlock(); }
    }

    void request(){
        lock.lock();
        try{
            while(connectionState == -1){
                awaitRequest.await();
            }
            
            if(connectionState == 2)
                return;
        }
        catch(Exception e){}
        finally{ lock.unlock(); }

        if(connectionState == 1) {
            lock.lock();
            try{
                requestingThreads++;
            }
            catch(Exception e){}
            finally{ lock.unlock(); }

            //make requests


            lock.lock();
            try{
                requestingThreads--;
                awaitClose.signalAll();
            }
            catch(Exception e){}
            finally{ lock.unlock(); }
        }
    }

    void close(){
        lock.lock();
        try{
            while(connectionState == -1){
                awaitClose.await();
            }

            if(connectionState == 2)
                return;
        }
        catch(Exception e){}
        finally{ lock.unlock(); }

        lock.lock();
        try{
            while(requestingThreads > 0){
                awaitClose.await();
            }
        }
        catch(Exception e){}
        finally{ lock.unlock(); }

    }
}