Question
Write a program that converts dates from numerical month/day/year format to normal “month day, year” format (for example, 12/25/2000 corresponds to December 25, 2000). You will define three exception classes, one called MonthException, another called DayException, and a third called YearException. If the user enters anything other than a legal month number (integers from 1 to 12 ), your program will throw and catch a MonthException and ask the user to reenter the month. Similarly, if the user enters anything other th an a valid day number (integers from 1 to either 28 , 29 , 30 , or 31, depending on the month and year), then your program will throw and catch a DayException and ask the user to reenter the day. If the user enters a year that is not in the range 1000 to 3000 (inclusive), then your program will throw and catch a YearException and ask the user to reenter the year. (There is nothing very special about the numbers 1000 and 3000 other than giving a good range of likely dates.) See Self-Test Exercise 19 in Chapter 4 for details on leap years.
Answer
import java.util.*;
public class DateConversion
{
public static int maximumDay(int monthNumber)
{
switch(monthNumber)
{
case 2:
return 28;
case 4:
case 6:
case 9:
case 11:
return 30;
default:
return 31;
}
}
public static int readMonthNumber() throws MonthException
{
Scanner input = new Scanner(System.in);
int month;
System.out.println("Enter month number:");
try
{
month = input.nextInt();
if(month <= 0 || month > 12)
throw new MonthException();
}
catch(InputMismatchException e)
{
throw new MonthException();
}
return month;
}
public static int readDayNumber(int month) throws DayException
{
Scanner input = new Scanner(System.in);
int day;
System.out.println("Enter day number:");
try
{
day = input.nextInt();
if(month != 2 && (day <= 0 || day > maximumDay(month)))
throw new DayException();
}
catch(InputMismatchException e)
{
throw new DayException();
}
return day;
}
public static int readYearNumber() throws YearException
{
Scanner input = new Scanner(System.in);
int year;
System.out.println("Enter year number:");
try
{
year = input.nextInt();
if(year <= 1000 || year > 3000)
throw new YearException();
}
catch(InputMismatchException e)
{
throw new YearException();
}
return year;
}
public static int checkFebruary(int day, int year) throws DayException
{
int maxDay = maximumDay(2);
if(year % 4 == 0)
maxDay++;
if(day <= 0 || day > maxDay)
{
throw new DayException();
}
else
return day;
}
public static String monthString(int monthNumber)
{
switch(monthNumber)
{
case 1:
return "January";
case 2:
return "February";
case 3:
return "March";
case 4:
return "April";
case 5:
return "May";
case 6:
return "June";
case 7:
return "July";
case 8:
return "August";
case 9:
return "September";
case 10:
return "October";
case 11:
return "November";
case 12:
return "December";
default:
System.out.println("Fatal Error");
System.exit(0);
return "Error";
}
}
public static void main(String args[])
{
int month = 1, day = 1, year = 1000;
boolean gotMonth = false;
while(!gotMonth)
{
try
{
month = readMonthNumber();
gotMonth = true;
}
catch (MonthException e)
{
System.out.println(e.getMessage());
}
}
boolean gotDay = false;
while(!gotDay)
{
try
{
day = readDayNumber(month);
gotDay = true;
}
catch (DayException e)
{
System.out.println(e.getMessage());
}
}
boolean gotYear = false;
while(!gotYear)
{
try
{
year = readYearNumber();
gotYear = true;
}
catch (YearException e)
{
System.out.println(e.getMessage());
}
}
if(month == 2)
{
boolean okFebruaryDate = false;
while(!okFebruaryDate)
{
System.out.println("Checking February date...");
try
{
day = checkFebruary(day, year);
okFebruaryDate = true;
}
catch(DayException e)
{
System.out.println(e.getMessage());
try
{
day = readDayNumber(month);
}
catch (DayException e1)
{
}
}
}
}
System.out.println("The date is " + monthString(month) + " " + day +", " + year);
}
}
public class MonthException extends Exception
{
public MonthException()
{
super("Invalid month.");
}
public MonthException(String message)
{
super(message);
}
}
public class DayException extends Exception
{
public DayException()
{
super("Invalid day.");
}
public DayException(String message)
{
super(message);
}
}
public class YearException extends Exception
{
public YearException()
{
super("Invalid year.");
}
public YearException(String message)
{
super(message);
}
}
Output:
Enter month number:
2
Enter day number:
28
Enter year number:
2015
Checking February date...
The date is February 28, 2015