Comparing Dates

[dougie1809]

Hi,

I am trying to write a method to compare date of births to one another. The code below is a method called compareTo(Date d) which takes in a Date object and tries to compare the date of birth of the another Date object?
Thanks

public int compareTo(Date d)
	{
		if(year > d.year || month > d.month || day > d.day)
			return 1;
		else if(year < d.year || month < d.month || day < d.day)
			return -1;
		else
		return 0;
	}

[sehudson]

What output are you seeing when you test it out, what is your question?

[dougie1809]

I am using this method in a sorting algorithm to try and sort the dates from youngest to oldest? And my outputs are not sorted which is below.
Thanks


1988/3/3
18/9/1988
17/9/1988
21/9/1976
2/3/1985
6/4/2
Bubble Sorted Dates Below
6/4/2
2/3/1985
21/9/1976
17/9/1988
18/9/1988
1988/3/3

I wasnt too sure what code tags I could place the output on?

[sehudson]

For one thing, it doesn't look like your dates are all formatted the same. What date is 6/4/2.
I would first look at your Date class, and make sure that it is in order first.

Where are you getting these dates from, is it a text file?

[dougie1809]

Well Im not concerned on the format of the dates, Il worry about that when I can get them sorting correctly, like I mean dates that are not correctly formatted will not effect the output of the result (They are just integers). I know that my compareTo(Date d) method is not correctly comparing the dates correctly, thats what I'd like to figure out?
No I am not using a text file but scanning them in from the keyboard when the program is in runtime.

Thanks

[sehudson]

So what does your bubble sorting routine look like?

[dougie1809]

The bubble sort method looks as follows below:
Thanks again

public static ArrayList<Date> bubbleSort(ArrayList<Date> dateList)
	{
		Date temp;
		int size = dateList.size();
	
		for(int x=0; x<size; x++)
		{
			for(int i=1; i<size-x; i++)
			{
				if(dateList.get(i-1).compareTo(dateList.get(i)) > 0)
				{
					temp = dateList.get(i);
					dateList.set(i, dateList.get(i-1));
					dateList.set(i-1, temp);
				}
			}
		}
		return dateList;
	}

[Tolls]

Hi,

I am trying to write a method to compare date of births to one another. The code below is a method called compareTo(Date d) which takes in a Date object and tries to compare the date of birth of the another Date object?
Thanks

public int compareTo(Date d)
	{
		if(year > d.year || month > d.month || day > d.day)
			return 1;
		else if(year < d.year || month < d.month || day < d.day)
			return -1;
		else
		return 0;
	}

That first if will consider a Date greater than another Date if either the year, month or day are greater.
So 15/07/2000 is after 12/12/2020 according to that logic.

[dougie1809]

Yes, thats my problem, a date could be ordered after another date if the day is higher, but does not take in the year. How could I get around that, so it will be looking at the date, and then the month, and then the day to determine who is younger to place in before an older person?
Thanks

[Tolls]

You need to expand your comparison.
If year1 > year 2 return 1.
else year1 == year 2 and month1 > month2 return 1...
etc.
There'll be better ways of organising it, but you need to get the base cases down.

[dougie1809]

Cheer that worked perfectly. I couldn't think of the logic of the method.
Thanks again