SynchronousQueue Example in Java - Produer Consumer Solution

SynchronousQueue is special kind of BlockingQueue in which each insert operation must wait for a corresponding remove operation by another thread, and vice versa. When you call put() method on SynchronousQueue it blocks until another thread is there to take that element out of the Queue. Similarly, if a thread tries to remove an element and no element is currently present, that thread is blocked until another thread puts an element into the queue. You can correlated SynchronousQueue with athletes (threads) running with Olympic torch, they run with torch (object need to be passed) and passes it to other athlete waiting at other end. If you pay attention to the name, you will also understand that it is named SynchronousQueue with a reason, it passes data synchronously to other thread; it wait for the other party to take the data instead of just putting data and returning (asynchronous operation). If you are familiar with CSP and Ada, then you know that synchronous queues are similar to rendezvous channels. They are well suited for hand-off designs, in which an object running in one thread must sync up with an object running in another thread in order to hand it some information, event, or task. In earlier multi-threading tutorials we have learned how to solve producer consumer problem using wait and notify, and BlockingQueue and in this tutorial we will learn how to implement producer consumer design pattern using synchronous queue. This class also supports an optional fairness policy for ordering waiting producer and consumer threads. By default, this ordering is not guaranteed. However, a queue constructed with fairness property set to true grants threads access in FIFO order.