Re: Help with Java program

DeAndrea Monroe wrote:


Based on what I saw in your Bank program, I think a fundamental concept
you might start your review with is the idea of what a class is. A
class encapsulates (groups together) attributes (class variables) and
methods (functions) that operate on the data of the class.

In the design of your bank simulator, you have identified that you have
customers, and the information about customers that you want to keep
track of is an integer representing the time at which they get to the
bank and how long (loop iterations) they have to wait for service.
Each customer that arrives at the bank will have their own arrival time
and their own wait time. So these will be class variables, and each
new customer object you create will have their own copies with the
associated values.

Some methods that a Customer object needs are the ability to set and
get the data in the class variables. These functions are called
mutators and accessors, respectively. An example of a mutator you need
is a function to increase the wait time by one unit every time through
the loop. An example of an accessor you need is a function to return
the final waiting time at the end of the run.

To create a class that descibes this design, your code might look
something like this:

class Customer
{
   private int arriveTime;
   private int waitTime;

   // mutator
   public void wait()
   {
      waitTime++;
   }

   // accessor
   public int getWaitTime()
   {
      return waitTime - arriveTime;
   }
}

Note that this is not complete. You still need a way to get data into
the arriveTime class variable. Maybe you want to make a mutator like
the one that updates waitTime. Another way would be to write a class
constructor that takes a variable parameter indicating the loop
iteration you're on and stores that in the arriveTime variable (which
is the concept I use below).

To create a queue of customers, then, in your main function (which is
NOT inside the braces for the Customer class, because your main
function is going to create and use Customer objects) you would maybe
have:

for (int customer = 0; customer < numCustomers; customer++)
{
   int randTime = ... // generate a random arrival time here
   Customer aCustomer = new Customer(randTime);
   // add aCustomer to the queue here
}

This will generate a queue of Customer objects, each one with its own
arrival time. Now use your loop and the Teller object to take
customers from the queue (adding the serviced customer's wait time to
an accumulator variable) and use the mutator on all the remaining
Customers in the queue to increment their wait times.

Etc.

One thing I've seen in your code is poor brace indentation discipline.
Using good indentation and lining up your block-enclosing braces will
help you see more easily what attributes and methods are in your
classes and what is not a member of it.

This information should point you in the right direction, at least.