ReadWrite locks

Data.java

public Object read() {
  synchronized(writeLock) {
    synchronized(readLock) {
      readersCount += 1;
    }
  }
  
  final Object result = value;
  
  synchronized(readLock) {
    readersCount -= 1;
    
    readLock.notify();
  }
  
  return result;
}

public void write(Object newValue) {
  synchronized(writeLock) {
    synchronised(readLock) {
       if (readersCount > 0) {
          readersCount.wait();
       }
    }
    
    value = newValue;
  }
}