Inheritance in Bob's Grocery Mart

Introduction

The Bob's Grocery Mart Simulator has been a big success. Cashiers are being scheduled more efficiently, and profits are up. However, Bob is concerned that some important factors are not captured by the current simulation. In particular, real customers occasionally leave the store before they reach the front of a checkout line, particularly if they have a long wait. Your goal for this assignment is to modify the simulation so that customers occasionally stop waiting and leave the store.

Instructions

• Download the following files:
  • Aisle.java
  • Customer.java
  • MartSimulation.java
  • MartDriver.java

• Create a new class that is a subclass of Aisle. Your new class should override the step method. The new version of step should perform exactly the same logic as the old version with the following difference: at the end of each time step, it should loop through the line of customers, and remove each customer with a small, fixed probability. This may not be the most realistic model of impatience, but it will have the desired effect that the longer a customer is forced to wait, the more likely it is that they will give up.

  You will need to iterate backwards through the list of customers, since removing a customer from the beginning of the list would move the rest of the customers down, causing you to skip customers in your loop.

  Your new class should not include a copy of the step logic from the parent class. That logic remains unchanged, and may be accessed using the super keyword.

  Since the line instance variable is currently private in the superclass, you will need to add an accessor method so that it can be modified in your subclass.

  Your class should include logic for tracking and reporting the number of customers that leave the line.

• Modify the simulation class so that it uses your new Aisle subclass. You should modify the constructor so that it accepts a "departure rate" parameter that describes the probability that a customer will leave during any 5 second time step.
• Modify the printResults method so that it reports the total number of customers that departed from all lines.
• Test your new simulation using two aisles, while keeping the other parameters at their default value. How many customers depart when the departure rate is 0.0? 1.0?, .01? .05? .1? (INCLUDE AN ANSWER TO THIS QUESTION IN A COMMENT AT THE BOTTOM OF YOUR NEW CLASS. )
• Submit your completed Aisle subclass and modified MartSimulation through canvas.
• If you have extra time: Each time this simulation is executed, there is a different result. It might be valuable to know the average results across many different simulation runs. Add a new method to the MartSimulation class with the signature:

  public void runMany(int numRuns)
  

  This method should run the simulation the indicated number of times, and calculate averages for each of the quantities reported.
• If you have even more time: It would be useful to be able to systematically adjust simulation parameters in small increments to see what effect this has on wait times etc. Add a loop to your main that slowly increases the departure rate from 0 to 1 in increments of .01. For each increment, run your simulation 100 times and report the average results.