Handling Concurrent Access of Shared Resource - Assignment Example

BurritoBrothers – Shop can be shared by multiple customers at a time, with a limit on a total number of customers. Counter Semaphore can be used to keep a check on a number of customers getting entry into Burrito Brothers shop. Per problem counter, semaphore should be initialized to '3'.Secondly, a binary semaphore to keep track of whether a customer is being served by a Server or not. This will avoid customer thread to gain access to multiple counters at a time.Cash Register - Like Counter location, the cash register is also shared by customers.

Since there exists a single cash register and only one customer can access it at a given moment. A binary semaphore can be used to control customers waiting to pay from paying together but would ensure they pay one by one.So, four different semaphores are needed to handle concurrency of Customer and Server as per the given problem. Both Customer and Server extend Thread class. However, both classes have different sets of responsibilities.Customer 1. Step into Burrito Brothers shop, if there is space available. 2. After stepping in, wait till the customer becomes a customer with the smallest order in waiting Area. 3. Once, a customer becomes the customer with the smallest order to acquire a free counter. 4. Leave counter and join waiting Area. 5. If more burritos are needed keep performing steps 3 & 4. 6. If an order is a complete wait for a cash register to get free. 7. Once the cash register is free to leave waiting Area and acquires cash register. 8. Pay. 9. Leave the cash register. 10. Leave Burrito Brothers. Server 1. Wait for the customer to serve. 2. Once the customer is at the counter, prepare three or fewer burritos. 3. Handover them and again go to step 1.

Additional, two classes are needed in the solution which is not mentioned in the class diagram. 1. CustomerGenerator - A class to generate new customers with random orders. 2. World - A class which creates. Since there exists a single cash register and only one customer can access it at a given moment. A binary semaphore can be used to control customers waiting to pay from paying together but would ensure they pay one by one. Since a customer with the smallest order needs to get a change to aquireCounter first Waiting Area is implemented as TreeSet which automatically sorts objects if the object implements Comparable interface.

Customers just need to check whether they are first in Tree Set to know whether they are eligible to acquire Counter Location, if available.