Second Lesson assignment for an intermediate Java course.

SalesWeek.java

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;

public class SalesWeek {

    public static Map<Day, ArrayList<Sale>> total_sales_day = new HashMap<Day, ArrayList<Sale>>(7);

    public SalesWeek() { };

    public enum Day {
        MONDAY("M"),
        TUESDAY("Tu"),
        WEDNESDAY("W"),
        THURSDAY("Th"),
        FRIDAY("F"),
        SATURDAY("Sa"),
        SUNDAY("Su");

        public final String abbr;
        private static final Map<String, Day> abbr_store = new HashMap<String, Day>(7);

        Day(final String abbr) {
            this.abbr = abbr;
        }

        public String getAbbr() {
            return this.abbr;
        }

        public List<Sale> getSales() {
            return SalesWeek.total_sales_day.get(this);
        }

        static {
            for (Day day : Day.values()) {
                abbr_store.put(day.getAbbr(), day);
            }
        }

        public static Day getDayByAbbr(String abbr) {
            return (abbr_store.containsKey(abbr) ? abbr_store.get(abbr) : null);
        }
    }

    public class Sale {

        private Day day_sold;
        private double price;

        public Sale(Day day, double price) {
            this.day_sold = day;
            this.price = price;
        }

        public double getPrice() {
            return this.price;
        }

        public Day getDaySold() {
            return this.day_sold;
        }
    }

    public void processSale(String info) {
        String[] split_data = info.split("\\,");
        try {
            Sale sale = new Sale(Day.getDayByAbbr(split_data[0]), Double.valueOf(split_data[1]));
            processSale(sale);
        } catch (java.lang.Exception e) {
            System.out.println("Invalid sales data!");
            e.printStackTrace();
        }
    }

    public void processSale(final Sale s) {
        List<Sale> sales_day = (s.getDaySold().getSales() == null ? new ArrayList<Sale>() : s.getDaySold().getSales());
        int idx = (sales_day.size() > 0 ? sales_day.size() - 1 : 0);
        sales_day.add(s);
        total_sales_day.put(s.getDaySold(), (ArrayList<Sale>) sales_day);
        System.out.println("Processed sale for [" + s.getDaySold().getAbbr() + "] for $" + s.getPrice() + ".");
    }

    public static List<String> getWeekStats() {
        List<String> stats = new ArrayList<String>();
        int d = 0;
        double week_income = 0, week_sales = 0, week_average = 0;
        for (Day day : Day.values()) {
            List<Sale> total_sales = total_sales_day.get(day);
            double total_income = 0;
            int total_sale_count = 0;
            double average_sale_price = 0;
            try {
                total_sale_count = total_sales.size();
                for (Sale s : total_sales) {
                    total_income += s.getPrice();
                }
                average_sale_price = (total_income / (double) total_sale_count);
            } catch (java.lang.NullPointerException e) {
                // this means that there were no sales on that day. so do nothing.
            }
            week_income += total_income;
            week_sales += total_sale_count;
            stats.add(d, String.format("Sales on [%s]: %s\nIncome on [%s]: $%f\nAverage of all sales on [%s]: %f",
                      day.toString(), total_sale_count, day.toString(), total_income, day.toString(), average_sale_price));
            d++;
        }
        week_average = (week_income / (double) week_sales);
        stats.add(d++, String.format("Week Sales: %s\nWeek Income: $%f\nWeek Sale Average: %f", week_sales, week_income, week_average));
        return stats;
    }

    public static void main(String[] args) {
        String in = "";
        SalesWeek sw = new SalesWeek();
        Scanner input = new Scanner(System.in);
        do {
            System.out.print("Please enter sales info (format: DayAbbr,Price): ");
            in = input.nextLine();
            if (!(in.equals("*"))) {
                sw.processSale(in);
            }
        } while (!(in.equals("*")));
        System.out.println("===================================\n"); // data separator..
        try {
            for (String sale_data : SalesWeek.getWeekStats()) {
                System.out.println(sale_data);
                System.out.println("-----");
            }
        } catch (java.lang.Exception e) {
            System.out.println("Caught an exception while getting total sales data!");
            e.printStackTrace();
            return;
        }
    }
}