Eggs.java

// need these to manage user input for order
import java.util.InputMismatchException;
import java.util.Scanner;

public class Eggs
{
    // boundary values for price break points by number of dozens
    private static final int[] BOUNDS = {0, 4, 6, 11};
    // per dozen prices corresponding to break points
    private static final double[] PRICES = {.5, .45, .4, .35};

    // for reading order input
    private static Scanner scan = new Scanner( System.in );

    public static void main( String[] args ) {
        int order = readOrder();    // get number of eggs

        int dozens = order/12;      // compute whole dozens
        int loose = order%12;       // compute loose eggs
        // identify price per whole dozen of eggs
        double pricePerDozen = getPricePerDozen( dozens );
        // compute the price per egg of loose eggs rounded to the
        // nearest whole cent
        double pricePerEgg = Math.floor( .5 + 50 * pricePerDozen) / 100;

        // report facts about order
        print( dozens, pricePerDozen, loose, pricePerEgg );
    }

    // get number of eggs for order
    private static int readOrder() {
        int order = 0;  // set return into method-global scope
        // read until valid input given
        while (true) {
            System.out.print(
                "How many eggs would you like to order" +
                " (must be a positive integer)?: "
            );
            try {
                order = scan.nextInt();
                if (0 < order ) break;
                System.out.println(
                    "invalid value: " + order + "\n" +
                    "input must be a positive integer"
                );
            }
            catch( InputMismatchException e ) {
                String sink = scan.next();
                System.out.println(
                    "invalid value: " + sink + "\n" +
                    "input must be a positive integer\n" +
                    e.toString()
                );
            }
            System.out.println( "" );
        }
        return order;
    }
    // based on size of order, determine which price is due
    private static double getPricePerDozen( int dozens ) {
        // determine index position of correct price by
        // comparing number of dozens ordered to price
        // break point boundaries
        int idx = 0;    // must be at least first index
        int last = BOUNDS.length - 1;
        // for each remaining break point boundary...
        for (;idx < last; idx++) {
            // if ordered number of dozens is less than
            // next boundary, increment index
            if (BOUNDS[ idx + 1 ] > dozens) break;
        }
        return PRICES[ idx ];
    }
    // report various aspects of order
    private static void print(
        int dozens, double pricePerDozen, int loose, double pricePerEgg
    ) {
        System.out.println(
            "The total price for an order of " +
            (12 * dozens + loose) + " eggs is " +
            getDollars(pricePerDozen * dozens + pricePerEgg * loose) + ".\n" +
            "That's " + getDollars( pricePerDozen ) + " per dozen for the " +
            dozens + " full dozen" + ((1 < dozens) ? "s":"") +
            " and " + getDollars( pricePerEgg ) + ((1 < loose) ? " (each)":"") +
            " for the " + loose + " loose egg" + ((1 < loose) ? "s":"") +"."
        );
    }
    // convert value to decimal format String with dollar sign -
    // values are rounded to nearest whole cent
    protected static final String getDollars( double d ) {
        String sd = "" + (int) Math.floor( .5 + 100 * d );
        return "$" + sd.substring( 0, sd.length() - 2) +
            "." + sd.substring( sd.length() - 2);
    }
}