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I am currently using the Udacity Introduction to Java course. There was a topic on Algorithms and it gave an example Algorithm for comparing and purchasing two different cars in pseudo code. I decided to turn that into some Java code to see just how well I grasped the concept.

The algorithm was:

For each car, compute. Gas cost = (miles driven / mpg) * price per gallon. Total cost = gas cost + car cost. If car 1 < car 2, buy car 1. Else, buy car 2.

//Algorithm for buying a car
//by comparing car price, MPG, 
//local gas price, and the miles 
//to be drive in total.
//idea from udacity Intro
//to Java course.


import java.util.Scanner;

public class buyingCars {

     public static void main (String[] args) {

            Scanner input = new Scanner(System.in);

            System.out.println("Enter the price of car one: ");
            int carOnePrice = input.nextInt();

            System.out.println("Enter the price of car two: ");
            int carTwoPrice = input.nextInt();

            System.out.println("Enter the price of gas in your area: ");
            double gasPrice = input.nextDouble();

            System.out.println ("What is the average mpg of car one? ");
            int carOneMpg = input.nextInt();

            System.out.println ("What is the average mpg of car two? " );
            int carTwoMpg = input.nextInt();

            System.out.println("Give me an amount of miles total you think you will drive in this car: ");
            int milesDriven = input.nextInt();

            double gasCostCarOne = (milesDriven / carOneMpg) * gasPrice;
            double totalCostCarOne = gasCostCarOne + carOnePrice;

            double gasCostCarTwo = (milesDriven / carTwoMpg) * gasPrice;
            double totalCostCarTwo = gasCostCarTwo + carTwoPrice;

            if (totalCostCarOne < totalCostCarTwo) {

                    System.out.println("Car One will, in total, cost less than car two. Buy it.");
            }

            else {

                    System.out.println("Car two will, in total, cost less than car one. Buy it.");
            }
      }
}

What I am wondering is if my code was clean and my form is good? Are there things I am doing in my code that I should not be, or is everything looking pretty solid?

Also, is there a simpler way of doing this? It just seems like an awful lot of code that could potentially be narrowed down. Could each car hold it's values in an array or something like that?

If there is a problem with my post, please let me know. I am still getting use to posting here.

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  • \$\begingroup\$ @PradeepSimha I can't find how to migrate it to codereview.. odd \$\endgroup\$
    – Mikhail
    Commented Jan 12, 2014 at 6:07
  • 1
    \$\begingroup\$ Regardless of your personal opinion, if you're asking a question here, your code needs to be here. \$\endgroup\$ Commented Jan 12, 2014 at 6:09
  • \$\begingroup\$ @chrylis Okay, I'll fix that. \$\endgroup\$
    – gabe.corsini
    Commented Jan 12, 2014 at 6:15
  • 1
    \$\begingroup\$ Well since Java is Object Oriented, you should design your code in a OO way. \$\endgroup\$
    – TwilightSun
    Commented Jan 12, 2014 at 6:30

2 Answers 2

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The first thing I would try is so factor out the input-prompting routines:

 private static Scanner input = new Scanner(System.in);

 private static int askInt(String prompt) {
     System.out.println(prompt);
     return input.nextInt();
 }

 private static double askDouble(String prompt) {
     System.out.println(prompt);
     return input.nextDouble();
 }

In my opinion, there's no particular reason why the car price, fuel efficiency, or distance numbers should be integral. Why not just do all of the work in doubles?

public class CarComparison {
     private static Scanner input = new Scanner(System.in);

     private static double ask(String prompt) {
         System.out.println(prompt);
         return input.nextDouble();
     }

     public static void main(String[] args) {
         double carOnePrice = ask("Enter the price of car one: ");
         double carTwoPrice = ask("Enter the price of car two: ");
         double gasPrice = ask("Enter the price of gas in your area: ");
         double carOneMpg = ask("What is the average mpg of car one? ");
         double carTwoMpg = ask("What is the average mpg of car two? ");
         double milesDriven = ask("Give me an amount of miles total you think you will drive in this car: ");

         double gasCostCarOne = (milesDriven / carOneMpg) * gasPrice;
         double totalCostCarOne = gasCostCarOne + carOnePrice;

         double gasCostCarTwo = (milesDriven / carTwoMpg) * gasPrice;
         double totalCostCarTwo = gasCostCarTwo + carTwoPrice;

         if (totalCostCarOne == totalCostCarTwo) {
             System.out.println("The two cars cost the same.");
         } else if (totalCostCarOne < totalCostCarTwo) {
             System.out.println("Car One will, in total, cost less than car two. Buy it.");
         } else {
             System.out.println("Car two will, in total, cost less than car one. Buy it.");
         }
      }
}

For completeness, I've added handling for the unlikely case of a tie.

A next step might be to define a totalCost() function or to define a Car object, but I think that for this problem, the benefits of further changes would be marginal, and I would just leave it at that.

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Seeing that you are at the start of your programming career. You are all good to go! Everything is nicely laid out. There are a lot of ways to make this "better" to other developers. But for your phase of learning you are right where you need to be! Good work keep coding!

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