CODEWITHSUNDEEP
javaandroiddateloops
TheLettuceMaster
TheLettuceMaster

Reputation: 15734

Loop through Months in Java / Android

I want to loop through months of the year and print out.

for example:

01/2012 02/2012 03/2012 04/2012 etc...

Here is my code:

 Calendar myDate = Calendar.getInstance();

 for (int i = 0; i < totalMonths; i++) {
        TableRow row = new TableRow(this);
        myDate.add(Calendar.MONTH, i);
        FinalDate = df.format(myDate.getTime());
        TextView tvNum = new TextView(this);
        tvNum.setText("      " + FinalDate);
        row.addView(tvNum);
        table.addView(row);
    }
}

It is printing out in int's

1 2 3 4 5

However, when I convert it to a date string, as seen in code above, it does this:

05/2012 06/2012 08/2012 11/2012 03/2013 08/2013

Basically, the gap of months is 1, then 2, then 3, then 4 etc... Are my calculations wrong? (showing the 1,2,3,4, etc list of int's is doing what it is supposed to be) or is there a better way through printing out months?

I just want it to go

today's date + 1 month today's date + 2 months etc... this m

Upvotes: 0

Views: 7955

Answers (4)

Anonymous
Anonymous

Reputation: 86324

java.time through desugaring

I should like to contribute the modern answer, the modern way to obtain your result. I recommend that these days you use java.time, the modern Java date and time API, for your date work. The others have nicely explained why your code gave an unexpected output, I am not repeating that.

    int noOfMonths = 13;
    YearMonth current = YearMonth.now(ZoneId.of("Africa/Tunis"));
    for (int i = 0; i < noOfMonths; i++) {
        System.out.println(current);
        current = current.plusMonths(1);
    }

When I ran this snippet today, the output was:

2019-01
2019-02
2019-03
2019-04
2019-05
2019-06
2019-07
2019-08
2019-09
2019-10
2019-11
2019-12
2020-01

If you want the month names, use a formatter:

    DateTimeFormatter monthFormatter = DateTimeFormatter.ofPattern("MMMM u", Locale.ENGLISH);
    int noOfMonths = 13;
    YearMonth current = YearMonth.now(ZoneId.of("Africa/Tunis"));
    for (int i = 0; i < noOfMonths; i++) {
        System.out.println(current.format(monthFormatter));
        current = current.plusMonths(1);
    }

Output:

January 2019
February 2019
March 2019
April 2019
May 2019
June 2019
July 2019
August 2019
September 2019
October 2019
November 2019
December 2019
January 2020

When this question was asked nearly 7 years ago, Calendar was the class we had for a task like this, also when it was poorly designed and cumbersome to work with. Not any longer: java.time came out with Java 8 just a couple of years later and has also been backported to Java 6 and 7.

Question: Doesn’t java.time require Android API level 26?

java.time works nicely on both older and newer Android devices. It just requires at least Java 6.

  • In Java 8 and later and on newer Android devices (from API level 26) the modern API comes built-in.
  • In non-Android Java 6 and 7 get the ThreeTen Backport, the backport of the modern classes (ThreeTen for JSR 310; see the links at the bottom).
  • On older Android either use desugaring or the Android edition of ThreeTen Backport. It’s called ThreeTenABP. In the latter case make sure you import the date and time classes from org.threeten.bp with subpackages.

Links

Upvotes: 1

JRaymond
JRaymond

Reputation: 11782

Instead of :

myDate.add(Calendar.MONTH, i);

put

myDate.add(Calendar.MONTH, 1);

or else create a new date every time. Currently you're manipulating your actual myDate Object.

Upvotes: 1

Tushar
Tushar

Reputation: 8049

Where do you define myDate? Outside the loop, I'm assuming? If so, then you're adding 0+0 the first time, (0+0)+1 the second time, (0+0+1)+2 the third time, etc.

To fix this, you have to define myDate inside the loop.

Upvotes: 1

SLaks
SLaks

Reputation: 887767

You're adding i months to the current date each time.

Therefore, the third iteration adds 2 months to the previous date, the fourth adds 3, etc.

You should be adding just 1 month each time.

Upvotes: 2

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