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Thread: Testing if dates are real or not.

  1. #1
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    Default Testing if dates are real or not.

    I'm having some trouble with this code that asks for input and then displays if it is a real date or not. We were given the first code and we had to write the second code based on a provided UML diagram. I finished writing the second one and got it to compile but it displays the wrong results such as Invalid Date: No such month every single time. I've reviewed the code several times and the logic makes sense to me, what am I missing?

    /*
    	Test program for Date class
    */
     
    import java.util.Scanner;
     
    public class Assignment5
    {
    	/* Test driver for Date class
     
    		Prompt for the number of Date objects to test, then create Date objects and determine
    		if they are valid dates.
     
    	*/
     
    	public static void main (String [] args)
    	{
    		Scanner keyboard = new Scanner(System.in);
     
    		int monthVal;
    		int dayVal;
    		int yearVal;
     
    		int maxLoop;
     
    		System.out.println ("Enter number of dates to test");
    		maxLoop = keyboard.nextInt();
     
    		for (int time = 0; time < maxLoop; time++)
    		{
    			System.out.println ("Enter the month, day and year separated by a space");
    			monthVal = keyboard.nextInt();
    			dayVal = keyboard.nextInt();
    			yearVal = keyboard.nextInt();
     
    			Date aDate = new Date (monthVal, dayVal, yearVal);
     
    			if (aDate.isValid())
    				System.out.println ("Valid Date: " + aDate);
    			else
    				System.out.println ("Invalid Date: " + aDate);
    			System.out.println();
    		}
    	}
    }


    and then here is the second code:

    public class Date
    {
    	private int month;
    	private int day;
    	private int year;
     
    	public Date (int month, int day, int year)
    	{
    		int newMonth = month;
    		int newDay = day;
    		int newYear = year;
     
    	}
     
    	public boolean isValid()
    	{
    		if (year >= 1582)
     
    			if(month >= 1 && month <=12)
     
    				if (month == 4 || month == 6 || month == 9 || month== 11)
     
    					if (day >=1 && day <= 30)
    						return true;
    					else
    						return false;
    				else
    					if (month == 2)
    						if (isLeapYear())
    							if (day >=1 && day <= 29)
    								return true;
    							else
    								return false;
    						else
    							if (day >= 1 && day <=28)
    								return true;
    							else
    								return false;
     
     
     
    					else
    						if (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12)
    							if (day >=1 && day <= 31)
    								return true;
    							else
    								return false;
    						else
    							return false;
     
    			else
    				return false;
    		else
    			return false;
     
    	}
     
    	public String toString()
    	{
    		switch (month)
    		{
    			case 1:
    				return "January" + "," + day + "," + year;
    			case 2:
    				return "February" + "," + day + "," + year;
    			case 3:
    				return "March" + "," + day + "," + year;
    			case 4:
    				return "April" + "," + day + "," + year;
    			case 5:
    				return "May" + "," + day + "," + year;
    			case 6:
    				return "June" + "," + day + "," + year;
    			case 7:
    				return "July" + "," + day + "," + year;
    			case 8:
    				return "August" + "," + day + "," + year;
    			case 9:
    				return "September" + "," + day + "," + year;
    			case 10:
    				return "October" + "," + day + "," + year;
    			case 11:
    				return "November" + "," + day + "," + year;
    			case 12:
    				return "December" + "," + day + "," + year;
    			default:
    				return "No such month";
    		}
    	}
     
    	private boolean isLeapYear()
    	{
    		if (year % 4 == 0)
     
    			if (year % 100 == 0 && year % 400 !=0)
    				return true;
     
    			else
    				return false;
     
    		else
    			return false;
    	}
    }


  2. #2
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    Default Re: Testing if dates are real or not.

    Take a close look at your Date constructor. By the way giving your class the same name as a class in the Java API can only lead to confusion.

  3. The Following User Says Thank You to Junky For This Useful Post:

    cardsfan33 (March 22nd, 2011)

  4. #3
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    Default Re: Testing if dates are real or not.

    Thank you I see the problem now within my constructor, and that part is functioning. Everything works except the leap year part. It still see February 29, 2008, for example, as an invalid date.

  5. #4
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    Default Re: Testing if dates are real or not.

    Obviously your algorithm in the isLeapYear method is wrong. Google for the correct algorithm.

  6. #5
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    Default Re: Testing if dates are real or not.

    Thanks once again! Much appreciated!

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