Description

• Marks: 3%
Prerequisite:
• Completed Lab 1
• Caught up to Unit 19 of Lecture Notes
• Familiar with CS2030S Java style guide
Goal
This is a continuation of Lab 1. Lab 2 changes some of the requirements of Lab 1 and adds some new things to the world that we are simulating. The goal is to demonstrate that, when OO-principles are applied properly, we can adapt our code to changes in the requirement with less effort.
Lab 2 also nudges you towards following good coding practice by adhering to a published coding convention.
Simulating a Shop with a Queue
Lab 2 adds an entrance queue to the shop. If all counters are busy when a customer arrives, the customer will join the queue and wait. When a counter becomes available, the customer at the front of the queue will proceed to the counter for service.
The entrance queue has a maximum queue length of m. If there are already m customers waiting in the entrance queue, any arriving customer will be turned away.
Building on Lab 1
You are required to build on top of your Lab 1 submission for this lab.
Assuming you have lab1-<username> and lab2-<username> under the same directory, and lab2-<username> is your current working directory, you can run
1 cp -i ..∕lab1-<username>∕*.java . 2 rm -i Lab1.java
to copy all your Java code over.
If you are still unfamiliar with Unix commands to navigate the le system and processing les, please review our Unix guide.
Skeleton for Lab 2
We only provide two classes for Lab 2, the main Lab2.java (which is simply Lab1.java renamed) and Queue.java .
Both les should not be modied for this lab.
The Queue class
Queue is a general class for a rst-in, rst-out queue of objects. Here is an example of how it is used:
1 ∕∕ Create a queue that holds up to 4 elements
2 Queue q = new Queue(4);
3
4 ∕∕ Add a string into the queue. returns true if successful; 5 ∕∕ false otherwise.
6 boolean b = q.enq(“a1”);
7
8 ∕∕ Remove a string from the queue. `Queue::deq` returns an 9 ∕∕ `Object`, so narrowing type conversion is needed. Returns 10 ∕∕ `null` is queue is empty.
11 String s = (String) q.deq();
12
13 ∕∕ Returns the string representation of the queue (showing
14 ∕∕ each element)
15 String s = q.toString();
16
17 ∕∕ Returns true if the queue is full, false otherwise.
18 boolean b = q.isFull();
19
20 ∕∕ Returns true if the queue is empty, false otherwise.
21 boolean b = q.isEmpty();
22
23 ∕∕ Returns the number of objects in the queue 24 int l = q.length();
Other Changes Needed
In addition to adding an entrance queue to the shop, we need to make the following changes to the input and output of the program.
There is an additional input parameter, an integer m, indicating the maximum allowed length of the entrance queue. This input parameter should be read immediately after reading the number of customers and the number of service counters.
A customer will now be printed with a single letter prex C . For instance, instead of Customer 1 , we print C1 .
A service counter will now be printed with a single letter prex S . For instance, instead of Counter 1 , we print S1 .
The entrance queue of the shop will be printed with the arrival event. E.g., the following shows that C3 arrived at time 1.400 and at the time of arrival, there are two customers, C1 and C2, waiting in the entrance queue.

If a customer joins the entrance queue, the customer along with the queue before joining should be printed. E.g.,

Following CS2030S Style Guide
In addition to the changes above, you should also make sure that your code follows the given Java style guide
Assumptions
We assume that no two events involving two different customers ever occur at the same time (except when a customer departs and another customer begins its service). As per all labs, we assume that the input is correctly formatted.
Your Task
Your task for this lab is to (i) improve upon your design for Lab 1 if needed, (ii) update
ShopSimulation and associated classes to simulate the entrance queue, (iii) update the input and output components of the classes to conform to the specication above.
If the design for Lab 1 follows the OOP principles, then only about 40 lines of changes/additions are required.
Compiling, Testing, and Debugging
Compilation
To compile your code,

Running and Testing
You should not test your code by manually entering the inputs. Instead, enter the inputs into a le, and run
A set of test inputs is provided as part of the skeleton, named Lab2.x.in under the inputs directory. You can run them with, for instance, You can save the output by redirecting it into a le.

You can automatically test your code against all the given inputs/outputs as well as

Debugging
The expected outputs are given in the outputs directory. You can compare OUT with the expected output with diff or vim . Using vim ,

will open both les and highlight the differences.
As the output becomes too long, you can focus on tracing a particular counter or customer with the help of grep . Suppose you want to focus on what happened to
Customer 1 in OUT , run
Submission
Upload the following les to CodeCrunch.
Lab2.java
any other .java les you use