CODEWITHSUNDEEP
javafor-loop
Bob_Danelou
Bob_Danelou

Reputation: 75

Java Using a for loop to print calendar (logic help)

I have this assignment due by the end of the month and I'm already halfway done. We had to use Zeller's congruence to calculate the day of the week that the 1st landed on. From that point (and accounting for leap years), you have to print off a calendar of the corresponding year using loops. The teacher said that this should be a really short program and we should not try to brute force the the logic of the program (basically, don' t use a bunch of if else and loops for each month). I already have the math calculations and leap year part down, but I can't wrap my head around how to make this for loop work for numerous reasons:

For example, I just started off writing a for loop just to see if I could print off a typical 31 day calendar without any special formatting (whitespaces, Month name, days etc). Here was my first test at using a for loop:

    for(int i = 1; i < 31; i++)
    {
        for(int j = 0; j < 7; j++)
        {


            System.out.print(i + "\t");
            i++;
            if(j == 6){
                i--;}

            if(i > 31)
            {
                break;
            }

        }
        System.out.print("\n");
    }

What is the logic behind using it for multiple months and whitespaces. I welcome all help, but please DO NOT GIVE ME SOURCE CODE. I want the satisfaction of getting this done with code I've written, and like I said, this is also an assignment and I won't really learn from copying and pasting code. Just throw me a bone about the logic I need to use. I can work in all other conditionals for special cases. Thanks guys.

Upvotes: 2

Views: 6970

Answers (2)

Gustek
Gustek

Reputation: 3760

I would write a function to display one month with parameters: dayOfWeek, numberOfDays, [name, firstDayOfWeek]

  • dayOfWeek - what day of week is 1st day of the month
  • numberOfDays - number of days in this month

optional parameters You may implement if You like

  • name - name of the month
  • firstDayOfWeek - some calendars use Sundays other use Mondays as first day, if You like to have this flexibility You can implement this as well.

And the logic is simple You can do with just one loop that would iterate numberOfDays+dayOfWeek-1 times. Inside You just need to check for end of week to make new lines and display empty spaces dayOfWeek-1 times in first week.

Upvotes: 1

Jack
Jack

Reputation: 133609

Ok, you need to manage something which varies between a fixed set of values, so you basically need a way to access these variable data from within a loop.

The best tool to fullfil this problem is probably an array.

If you store inside an array, for example the duration of the months you will be able to access them in a straightforward way (through an index) so that you won't need any conditional chain, you will just need the index of the current month, eg monthDurations[i] == 31.

If you want to structure everything better you could define your own Month class or Day class or whatever you need to keep track of printing issues (eg white spaces or names) so that everything will be easily encapsulated and maintainable.

Upvotes: 1

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