How can change my code so results are based on user input of years and days?

I have written the code below to calculate the date of "two years ago" based off the "today's date", as well as the date of "5 days ahead".

I want to make a dynamic version of the code, follow开发者_运维技巧ing the same comparison principle. For example, I want the user to insert the numbers of years and days and compare it to today's date.

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Code:

public class Calendar1{
    private static void doCalendarTime() {
        System.out.print("*************************************************");
        Date now = Calendar.getInstance().getTime();
        System.out.print("  \n Calendar.getInstance().getTime() : " + now);
        System.out.println();
    }

    private static void doSimpleDateFormat() {
        System.out.print("*************************************************");
        System.out.print("\n\nSIMPLE DATE FORMAT\n");
        System.out.print("*************************************************");
        // Get today's date
        Calendar now = Calendar.getInstance();
        SimpleDateFormat formatter = new SimpleDateFormat("E yyyy.MM.dd 'at' hh:mm:ss a zzz");
        System.out.print(" \n It is now : " + formatter.format(now.getTime()));
        System.out.println();
    }

    private static void doAdd() {
        System.out.println("ADD / SUBTRACT CALENDAR / DATEs");
        System.out.println("=================================================================");
        // Get today's date
        Calendar now = Calendar.getInstance();
        Calendar working;
        SimpleDateFormat formatter = new SimpleDateFormat("E yyyy.MM.dd 'at' hh:mm:ss a zzz");
        working = (Calendar) now.clone();
        working.add(Calendar.DAY_OF_YEAR, - (365 * 2));
        System.out.println ("  Two years ago it was: " + formatter.format(working.getTime()));
        working = (Calendar) now.clone();
        working.add(Calendar.DAY_OF_YEAR, + 5);
        System.out.println("  In five days it will be: " + formatter.format(working.getTime()));
        System.out.println();
    }

    public static void main(String[] args) {
        System.out.println();
        doCalendarTime();
        doSimpleDateFormat();
        doAdd();

    }
}

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Java's standard date-time APIs are not very good for operations on dates. If you want to do real calculations on dates, I suggest a library like Joda-Time, which has much better functionality for such cases.

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Here is the a Joda-Time code following the same example used on the question:

DateTime now = new DateTime();
DateTime twoYearsAgo = now.minusYears(2);
DateTime fiveDaysFromNow = now.plusDays(5);

DateTimeFormatter formatter = new DateTimeFormatterBuilder()
   .appendPattern("E yyyy.MM.dd 'at' hh:mm:ss a zzz")
   .toFormatter();

System.out.println(formatter.print(twoYearsAgo));
System.out.println(formatter.print(fiveDaysFromNow));

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This assumes you want to work with the system's default time-zone (meridian). If that is not the case, there is a constructor's argument to set the time-zone that will be used.