Date Comparison Program - Help!

[Chris Hathaway]

Hi, I am currently developing a program that will allow you to enter in two dates and it will tell you the difference between them. Im currently having problems getting the months to properly work, the way I want it to work is that the user enters in the month(such as january or april) for each date, and a year for each date(such as 2012 or 1776). The year difference works fine, but for the months I cant seem to figure it out, any help would be greatly appreciated! Here is my code so far!
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/*Variables:

 *There are variables for each month of the year, also including spaces for year one and two, months one and two,

 *and the differences between the months and the years.

 *

 *Input:

 *The user inputs the months and the years for two different dates to be compared

 *

 *

 *Processing:

 *it compares the years to see which one is bigger, then subtracts the bigger year from the smaller year.

 *then looks to see which month the user typed in, giving it a number value

 *

 *

 *Output:

 *It prints out the user inputed dates, then prints out the difference in the two dates

 *by months and years.

 *

 *

 */



import java.util.Scanner;

import java.lang.String;



public class DateComparison

{


public static void main (String[] args)

 {


 //Variables

 String monthnumberone, monthnumbertwo;

 int firstmonthnumber = 0, secondmonthnumber = 0;

 int yearnumberone, yearnumbertwo, yeardifference = 0, monthdifference = 0;

 Scanner scan = new Scanner(System.in);



 //Input


 System.out.println("For the first date...");

 System.out.print("Enter month: ");

 monthnumberone = scan.next();

 System.out.print("Enter Year: ");

 yearnumberone = scan.nextInt();


 System.out.println();


 System.out.println("For the first date...");

 System.out.print("Enter month: ");

 monthnumbertwo = scan.next();

 System.out.print("Enter Year: ");

 yearnumbertwo = scan.nextInt();



 //Processing



  //Month Number 1


 if (monthnumberone.equalsIgnoreCase("January"))

   {

    firstmonthnumber = 1;

   }

 if (monthnumberone.equalsIgnoreCase("February"))

   {

    firstmonthnumber = 2;

   }

 if (monthnumberone.equalsIgnoreCase("March"))

   {

    firstmonthnumber = 3;

   }

 if (monthnumberone.equalsIgnoreCase("April"))

   {

    firstmonthnumber = 4;

   }

 if (monthnumberone.equalsIgnoreCase("May"))

   {

    firstmonthnumber = 5;

   }

 if (monthnumberone.equalsIgnoreCase("June"))

   {

    firstmonthnumber = 6;

   }

 if (monthnumberone.equalsIgnoreCase("July"))

   {

    firstmonthnumber = 7;

   }

 if (monthnumberone.equalsIgnoreCase("August"))

   {

    firstmonthnumber = 8;

   }

 if (monthnumberone.equalsIgnoreCase("September"))

   {

    firstmonthnumber = 9;

   }

 if (monthnumberone.equalsIgnoreCase("October"))

   {

    firstmonthnumber = 10;

   }

 if (monthnumberone.equalsIgnoreCase("November"))

   {

    firstmonthnumber = 11;

   }

 if (monthnumberone.equalsIgnoreCase("December"))

   {

    firstmonthnumber = 12;

   }




   //Month Number 2

 

  if (monthnumbertwo.equalsIgnoreCase("January"))

    {

     secondmonthnumber = 1;

    }

  if (monthnumbertwo.equalsIgnoreCase("February"))

    {

     secondmonthnumber = 2;

    }

  if (monthnumbertwo.equalsIgnoreCase("March"))

    {

     secondmonthnumber = 3;

    }

  if (monthnumbertwo.equalsIgnoreCase("April"))

    {

     secondmonthnumber = 4;

    }

  if (monthnumbertwo.equalsIgnoreCase("May"))

    {

     secondmonthnumber = 5;

    }

  if (monthnumbertwo.equalsIgnoreCase("June"))

    {

     secondmonthnumber = 6;

    }

  if (monthnumbertwo.equalsIgnoreCase("July"))

    {

     secondmonthnumber = 7;

    }

  if (monthnumbertwo.equalsIgnoreCase("August"))

    {

     secondmonthnumber = 8;

    }

  if (monthnumbertwo.equalsIgnoreCase("September"))

    {

     secondmonthnumber = 9;

    }

  if (monthnumbertwo.equalsIgnoreCase("October"))

    {

     secondmonthnumber = 10;

    }

  if (monthnumbertwo.equalsIgnoreCase("November"))

    {

     secondmonthnumber = 11;

    }

  if (monthnumbertwo.equalsIgnoreCase("December"))

    {

     secondmonthnumber = 12;

    }


 


  if (yearnumberone > yearnumbertwo)

    {

     yeardifference = (yearnumberone - yearnumbertwo);

    }

  if (yearnumberone < yearnumbertwo)

    {

      yeardifference = (yearnumbertwo - yearnumberone);

    }


    //Month Difference

  if (firstmonthnumber > secondmonthnumber)

    {

     monthdifference = (firstmonthnumber - secondmonthnumber);

    }



 //Output


 System.out.println("These dates are: " + (yeardifference) + " years and " + (monthdifference) + " months apart.");











 }



}

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[Tim Moores]

Can you give an example of an input where the code does not do what you expected it to do? I see that for years you're handling the case where one value might be smaller or larger than the other, whereas for months you don't do that. Maybe start by fixing that.

Once you're a bit further down the road, check out the java.text.SimpleDateFormat class - it can convert characters strings containing month names to numbers much more easily than what you're doing here.

[Winston Gutkowski]

Chris Hathaway wrote:Im currently having problems getting the months to properly work...

What Tim said. Are you familiar with methods yet? Because you could use them to eliminate a lot of the repeated code in your program.
Also, for calculation purposes, you may find it easier to number your months from 0 to 11. For one thing, you can then use them as indexes, and for the calculations themselves you probably won't have to add '±1' as often.

If this isn't just an exercise, you may also want to look at Joda Time; I'm pretty certain that its Interval class will already do everything you want.

Oh, and BTW, I really like your field naming. Very clear and easy to follow. For true adherence to convention, you might want to get into the habit of using camel case (eg, monthNumberTwo, rather than monthnumbertwo), but other than that it's very good; and you'd be surprised how many newbies get that part wrong. Keep it up.


Winston