Computer Science 523
Advanced Programming
Summer 2014, The College of Saint Rose
PurchaseTrackerAll BlueJ Project
Click here to download a BlueJ project for PurchaseTrackerAll.
PurchaseTrackerAll Source Code
The Java source code for PurchaseTrackerAll is below. Click on a file name to download it.
/*
* Example PurchaseTrackerAll: test out a class that stores items
* purchased and their quantities, this time remembering all
* of the items we read in and determining the "winners" at the end.
*
* Jim Teresco, The College of Saint Rose, CSC 523, Summer 2014
*
* $Id: PurchaseTrackerAll.java 2377 2014-06-10 03:12:01Z terescoj $
*/
import java.util.ArrayList;
import java.util.Scanner;
public class PurchaseTrackerAll {
// A private method to prompt for and read in a valid item
// from the given Scanner, returning a PurchasedItem object,
// returns null if no item is entered.
// The existence of this method avoids some repeated code in
// main and also would be able to be used for any Scanner,
// not just ones based on the standard input, and would be
// a convenient place to add error checking on the input
// values (for example, ensure positive values for price
// and quantity or the addition of some exception handling
// to recover from invalid inputs).
private static PurchasedItem readPurchasedItem(Scanner s) {
System.out.println("Enter the item name, unit price, and quantity purchased, \"done\" to stop:");
String itemName = s.next();
// if someone typed "done", we return null and don't try to read the other fields
if (itemName.equals("done")) return null;
double unitPrice = s.nextDouble();
int quantity = s.nextInt();
return new PurchasedItem(itemName, unitPrice, quantity);
}
public static void main(String[] args) {
// create a keyboard Scanner to read lines that describe the items
Scanner keyboard = new Scanner(System.in);
// create an ArrayList of PurchasedItem objects to store all of them
ArrayList<PurchasedItem> items = new ArrayList<PurchasedItem>();
PurchasedItem item;
// now read them all in
do {
item = readPurchasedItem(keyboard);
if (item != null) {
items.add(item);
}
} while (item != null);
// if there was no valid item entered, we just quit
if (items.isEmpty()) {
System.out.println("No valid item purchases entered, exiting...");
System.exit(0);
}
// so we know we have one valid item in the ArrayList, so we
// initialize the "leader" in each category to be the first item (position 0)
item = items.get(0);
PurchasedItem leastExpensiveItem = item;
PurchasedItem mostExpensiveItem = item;
PurchasedItem largestQuantity = item;
PurchasedItem highestTotalCost = item;
System.out.println("All items:");
System.out.println(item);
// now we can loop over the remaining, printing each and deciding
// which are the "winners"
for (int itemNum = 1; itemNum < items.size(); itemNum++) {
item = items.get(itemNum);
System.out.println(item);
// do we have any new leaders?
if (item.getUnitPrice() < leastExpensiveItem.getUnitPrice()) {
leastExpensiveItem = item;
}
if (item.getUnitPrice() > mostExpensiveItem.getUnitPrice()) {
mostExpensiveItem = item;
}
if (item.getQuantity() > largestQuantity.getQuantity()) {
largestQuantity = item;
}
if (item.getTotalCost() > highestTotalCost.getTotalCost()) {
highestTotalCost = item;
}
}
// now report our winners:
System.out.println("Least expensive item: " + leastExpensiveItem);
System.out.println("Most expensive item: " + mostExpensiveItem);
System.out.println("Largest quantity item: " + largestQuantity);
System.out.println("Highest total cost item: " + highestTotalCost);
}
}
/**
* A custom class to represent a purchased item based on name,
* unit price, and a quantity purchased.
*
* @author Jim Teresco
*
* $Id: PurchasedItem.java 2377 2014-06-10 03:12:01Z terescoj $
*/
import java.text.DecimalFormat;
public class PurchasedItem {
// we need instance variables to remember the
// name, unit price, and quantity
private String name;
private double unitPrice;
private int quantity;
// we can create a static class variable that refers to
// a single DecimalFormat object that can be shared among
// all instances of this class
private static DecimalFormat currency = new DecimalFormat("$0.00");
// our constructor needs the initial values for the three
// fields in our object
public PurchasedItem(String name, double unitPrice, int quantity) {
this.name = name;
this.unitPrice = unitPrice;
this.quantity = quantity;
}
// we'll need a toString method
public String toString() {
return name + ": " + quantity + " @ " + currency.format(unitPrice) +
" = " + currency.format(unitPrice * quantity);
}
// a variety of accessors are needed here, and here they are
public double getUnitPrice() {
return unitPrice;
}
public int getQuantity() {
return quantity;
}
public double getTotalCost() {
return unitPrice * quantity;
}
}