HW1

.gitignore

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+/out/
+.idea/
+OOD.iml

src/HW1/BetterDiningHallSimulation.java

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+package HW1;
+
+import java.util.ArrayList;
+
+public class BetterDiningHallSimulation
+{
+    private static final int SIMULATION_TIME = 50000;  // A simulation is for 50,000 imaginary seconds.
+    private static final int CUST_ARRIVAL_PCT = 18;    // There is a 18% chance a customer arrives each second.
+    private static final int NUM_REGISTERS = 4;        // There are 4 cash registers.
+
+    private static ArrayList<CashRegister> registers = new ArrayList<>();
+
+    // statistics about the cash registers
+    private static int[] customersServed = new int[NUM_REGISTERS]; // del HW1.CashRegister
+    private static int[] totalWaitTimes = new int[NUM_REGISTERS]; // del HW1.Customer
+
+    public static void main(String[] args)
+    {
+        // First, initialize the cash register arrays.
+        for (int r = 0; r < NUM_REGISTERS; r++)
+            registers.add(new CashRegister());
+
+        // Then perform the simulation for the specified number of seconds.
+        for (int t = 0; t < SIMULATION_TIME; t++)
+        {
+            if (aCustomerArrives())
+            {
+                Customer newCustomer = new Customer();
+                newCustomer.smallestRegister(registers).addCustomerInLine(newCustomer);
+            }
+
+            for (CashRegister register : registers)
+                register.elapseOneSecond();
+        }
+
+        // Print out the statistics.
+        for (int r = 0; r < NUM_REGISTERS; r++)
+        {
+            CashRegister register = registers.get(r);
+
+            System.out.println("Register " + r);
+            System.out.println("\tNumber of arrivals = " + register.getCustomersServed());
+            System.out.println("\tAverage wait time = " + register.getAverageWaitTime());
+        }
+    }
+
+    // keep this here because it is driving the simulation
+    private static boolean aCustomerArrives()
+    {
+        int n = (int) (Math.random() * 100);  // an integer between 0 and 99
+        return n < CUST_ARRIVAL_PCT;
+    }
+}

src/HW1/CashRegister.java

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+package HW1;
+
+import java.util.ArrayList;
+
+public class CashRegister
+{
+    private ArrayList<Customer> customersInLine = new ArrayList<>();
+    private int customersServed = 0;
+    private int totalWaitTime = 0;
+
+    public void addCustomerInLine(Customer customer)
+    {
+        customersInLine.add(customer);
+        totalWaitTime += customer.getWaitTime();
+    }
+
+    public void customerServed(Customer customer)
+    {
+        customersInLine.remove(customer);
+        customersServed++;
+    }
+
+    public int getCustomersServed()
+    {
+        return customersServed;
+    }
+
+    public int getLine()
+    {
+        return customersInLine.size();
+    }
+
+    public int getAverageWaitTime()
+    {
+        return totalWaitTime / customersServed;
+    }
+
+    public void elapseOneSecond()
+    {
+        // If the list is empty, there are no customers to process.
+        if (getLine() == 0)
+            return;
+
+        // Otherwise, the first customer in line gets processed.
+        if (customersInLine.get(0).waited() <= 0)
+        {
+            // First update the register's statistics.
+            customersServed++;
+
+            // Then remove the customer.
+            customersInLine.remove(0);
+        }
+    }
+}

src/HW1/Customer.java

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+package HW1;
+
+import java.util.List;
+
+public class Customer
+{
+    // is the wait time the customer is going to have
+    private int waitTime;
+
+    public Customer()
+    {
+        this.waitTime = 2 * howManyItems() + 10;
+    }
+
+    // determines how many items this customer is going to get
+    private int howManyItems()
+    {
+        int n = (int) (Math.random() * 10);
+        return n + 1;
+    }
+
+    // determines the shortest line for the customer to go to
+    public CashRegister smallestRegister(List<CashRegister> registers)
+    {
+        CashRegister smallestLine = null;
+
+        for (CashRegister register : registers)
+        {
+            if (smallestLine == null || register.getLine() < smallestLine.getLine())
+                smallestLine = register;
+        }
+
+        return smallestLine;
+    }
+
+    public int getWaitTime()
+    {
+        return waitTime;
+    }
+
+    public int waited()
+    {
+        waitTime--;
+        return waitTime;
+    }
+}