Develop Reference

Add one day to calendar to make test if-else

I use DateTime values in my app. I can create Lessons, and I have to set the beginning nd the end of that lesson.
Let's say I create like this :
English - Beginning 07.05.2017 End 07.07.2017
Then I want to modify the end of that lesson and put :
07.06.2017
I check to see if the dates are OK, but I'm not sure about what I did, because I dont want to let the user to modifiy or create lessons in the past, but if he creates a lesson that finishes the current day, that's ok.
I wrote like this in my if else :
String date1 = datedebut.getText().toString();
String date2 = datefin.getText().toString();
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
Date date_debutnew = dateFormat.parse(date_initial);
Date date_derniernew = dateFormat.parse(date_derniercours);
Calendar calendar = Calendar.getInstance();
if (date_debutnew.after(date_derniernew) || date_derniernew.before(calendar.getTime()))
{ ... }
How can I add one day to that calendar ?
Thank you for the future hlep.

You can use compareTo() method of Date.
It will return,
a value 0 if the argument Date is equal to this Date;
a value less than 0 if this Date is before the Date argument;
a value greater than 0 if this Date is after the Date argument.

From what I understand of the problem, your new Finish date should be after the new Start date and before the designated end Date.
so, the condition should be :
if (date_derniernew.after(date_debutnew) || date_derniernew.before(date2)) {
..}

Android - How to add days to date

I have retrieved a Date from a SQLiteDatabase and have formatted it to how I want via the following;
String steepingDate = (c.getString(3));
SimpleDateFormat formatter = new SimpleDateFormat("dd/MMM/yyyy");
Date steepingdate = formatter.parse(steepingDate);
I now want to give the user the option to increase whatever date is in steepingdate by a certain amount of days that the user can input
I know you can use;
Date today = calendar.getTime();
calendar.add(Calendar.DAY_OF_YEAR, 10);
For example to add 10 days onto todays date
But how do you do it so that it uses steepingdate instead of todays date
Thanks
UPDATE;
The calendar is working as I want, but I now want to save the new data to the database, the full code is as following;
String steepingDate = (c.getString(3));
SimpleDateFormat formatter = new SimpleDateFormat("dd/MMM/yyyy");
Date steepingdate = formatter.parse(steepingDate);
Integer amountDays = Integer.parseInt(TSExtend.getText().toString());
Calendar ca = Calendar.getInstance();
ca.setTime(steepingdate);
ca.add(Calendar.DAY_OF_YEAR, amountDays);
DateFormat dateFormat = new SimpleDateFormat("dd/MMM/yyyy");
String newDate = dateFormat.format(ca);
I'm getting the error;
Bad class: class
java.util.GregorianCalendar
Any ideas?

To add 10 days to steepingdate, you can use:
Calendar calendar = Calendar.getInstance();
calendar.setTime(steepingdate);
calendar.add(Calendar.DAY_OF_YEAR, 10);
it the number is provided, through the user interface, you can use the View.OnClickListener and when onClick is fired, read the value from an EditText, and use this value instead of 10

Set the time of the calendar to your date, then add the days
Calendar cal = Calendar.getInstance();
cal.setTime(steepingdate);
cal.add(Calendar.DATE, 10);
UPDATE:
You can't directly format a Calendar, first get the Date from the Calendar, then format it.
String newDate = dateFormat.format(ca.getTime());

How to add holidays in Android Calendar?

I am trying to add a list of holidays to my calendar. I am using the Caldroid library for displaying the calendar. I want to display a list of holidays in every month for which I need to select specific dates in every month. How do I do that ? The following is what I have tried:
CODE :
Calendar cal = Calendar.getInstance();
cal.add(Calendar.DATE, -18);
Date blueDate = cal.getTime();
cal = Calendar.getInstance();
cal.add(Calendar.DATE, 16);
int diff = cal.get(Calendar.JANUARY);
cal.add(diff, 10);
Date greenDate = cal.getTime();
I believed that diff would set the month to January and highlight the 11th of January cause I have given the value as 10 but it doesn't do so and I believe it is because I have instantiated the cal to getInstance() which would return the current month.
UPDATE :
Thanks to Meno, I have achieved the following but when I set the calendar to the second time, it takes only the updates value and does not set the first date (very obvious) but I want to know how to set multiple dates in a month without re-instantiating a new GregorianCalendar object for every month. Simply put, how do I set an array of dates in a month.
GregorianCalendar greg_cal = new GregorianCalendar();
greg_cal.set(Calendar.MONTH, Calendar.JANUARY);
greg_cal.set(Calendar.DAY_OF_MONTH, 1);
greg_cal.set(Calendar.MONTH, Calendar.JANUARY);
greg_cal.set(Calendar.DAY_OF_MONTH, 18);
Thanks in advance.

Your question does not appear to be clear. Nevertheless I try an answer. Instead of
cal = Calendar.getInstance(); // In Thailand this gives the buddhist calendar, do you want this?
cal.add(Calendar.DATE, 16); // 16 days from now, what is the intention or meaning???
cal.add(diff, 10); // first argument must be a defined constant in java.util.Calendar
I assume you just want to select a fixed date (as holiday). If so then you can call the set()-method and don't need to add days to move your calendar date forth and back:
GregorianCalendar cal = new GregorianCalendar(); // including currrent year
cal.set(Calendar.MONTH, Calendar.JANUARY);
cal.set(Calendar.DAY_OF_MONTH, 11);
Then you get as date the 11th of January in current year. By the way:
int diff = cal.get(Calendar.JANUARY);
This line is nonsense because:
Calendar.JANUARY is an int constant which is zero and denotes a value (the month) not a field. But the get(int)-method expects a field constant. The field constant with value zero corresponds to Calendar.ERA. Finally the line yields the era of cal, namely int diff = GregorianCalendar.AD = 1; assuming you use the gregorian calendar. This is surely not what you want???
UPDATED because of extra question in comment:
Reusing means that you don't create a new instance for the next calculation but reuse the same one (GregorianCalendar is mutable!). For example:
GregorianCalendar cal = new GregorianCalendar(); // including currrent year
cal.set(Calendar.MONTH, Calendar.JANUARY);
cal.set(Calendar.DAY_OF_MONTH, 11);
Date holiday1 = cal.getTime();
cal.set(Calendar.MONTH, Calendar.DECEMBER); // no new instance => reuse cal
cal.set(Calendar.DAY_OF_MONTH, 24);
Date holiday2 = cal.getTime();
...
I have also written about limiting to manipulations of month and day-of-month only because with manipulation of week-related fields the state of reused Calendar-instance depends on the order of field manipulations (very ugly and surprising).
Anyway, it is always safer to use immutable types which are available in Java 8 (not useable on Android), JodaTime and my alpha-state-library. I admit that the first contact with JodaTime can cause you feeling like lost because there are so many methods (the documentation standard is good for open-source but less good than for example in JSR-310). In your use-case I would use the type org.joda.time.LocalDate as start because you really have just a plain-date-use-case. Google and SO are your friends if you want to see more documentation beyond the original Joda documentation.
UPDATE due to extended question:
You have forgotten one important thing in your new code, namely to add the results of calendar setting to a holiday list, see here the modification:
List<Date> holidays = new ArrayList<Date>();
GregorianCalendar greg_cal = new GregorianCalendar();
greg_cal.set(Calendar.MONTH, Calendar.JANUARY);
greg_cal.set(Calendar.DAY_OF_MONTH, 1);
holidays.add(greg_cal.getTime());
greg_cal.set(Calendar.MONTH, Calendar.JANUARY);
greg_cal.set(Calendar.DAY_OF_MONTH, 18);
holidays.add(greg_cal.getTime());
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
for (Date d : holidays) {
System.out.println(sdf.format(d));
}
// output:
2014-01-01
2014-01-18
In an external library like JodaTime you would just use org.joda.time.LocalDate instead.
List<LocalDate> holidays = new ArrayList<LocalDate>();
LocalDate today = LocalDate.now();
holidays.add(today.withMonthOfYear(1).withDayOfMonth(1));
holidays.add(today.withMonthOfYear(1).withDayOfMonth(18));
It is pretty simple (similar in my unfinished date-and-time-library, too).

date retreival in android

In my application i have 2 field, 1 is date and another is recc(is an integer) in database table.
Now i will explain my requirement:
Consider suppose user enters today's date(26-07-2012) and recc as 10.It means that starting from today's date to that +10 date.I got that 10th date from today's date.But what i want is 10th day from today's date means it will surely go to next month also (26-07-2012----5-08-2012),but i have to know the count of date which falls in this particular month,(i.e)between 26-07-2012----5-08-2012 how many days it will fall within this month.I think i have explained my problem clearly,if not i am ready to give more explanation.Thanks in advance.
Date value:
EditText date=(EditText)findViewById(R.id.startdateexp);
String startdate=date.getText().toString();

you can do this by following way:
1. Get date from Database.
Now get day of month from the date by following method:
DateFormat iso8601Format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
try {
date = iso8601Format.parse(dateTime);
} catch (ParseException e) {
Log.e(TAG, "Parsing ISO8601 datetime failed", e);
}
Calendar cal=Calendar.getInstance();
cal.setTime(date);
int currentDay= cal.get(Calendar.DAY_OF_MONTH);
calculate Last day of month by:
int lastDay = cal.getActualMaximum(Calendar.DAY_OF_MONTH);

If you're using the Date class you can offset it by the number of days converted to milliseconds to create a new Date:
Date datePlusRecc = new Date(oldDate.getTime() + recc*86400000); // 86400000 = 24*60*60*1000
Note that this is useable only when recc is relatively small (< about 20), because otherwise the multiplication will overflow.

Just use the java.util.Date class combined with your date in milliseconds.
In a for loop add one day to the one version in milliseconds and convert it back to Date. Get the Month out of the Date Object and compare it with the current month. As soon as the month is a new one you have your total count of days in the current month.
Date currentDate = new Date(currentMillis);
long countingMillis = currentMillis;
int daysInSameMonth = 0;
while(true){
daysInSameMonth++; // if the actual date schould not count move this line at the button of the while
countingMillis += 1000*60*60*24;
Date dt = new Date(countingMillis);
if(currentDate.getMonth() != dt.getMonth())
break;
}

how to add no days to date object not calendar object

I have a Date object. Now I want to add days to that Date object.
So how that can be done? Actually using Calendar object that can be done I know.
But in my case, I haven't used a calendar objects. Instead only used date object.
For Example, suppose I have a date object
Date dtStartDate=o.getStartDate();
int x=28;
Now what I want to do is to add 28 to this date object, means if the dtStartDate is 1 July 2011
then after adding 28, dtStartDate will be 29 July 2011.
Please suggest it to me.
Thanks in advance

You can add Day using below
Calendar c1 = Calendar.getInstance();
c1.add(Calendar.DAY_OF_MONTH, 1);
Here 1 is number of Day you can add.
OR
Date dtStartDate=o.getStartDate();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm");
Calendar c = Calendar.getInstance();
c.setTime(dtStartDate);
c.add(Calendar.DATE, 3); // number of days to add
String dt = sdf.format(c.getTime()); // dt is now the new date
Toast.makeText(this, "" + dt, 5000).show();
May be your problem solved.

You could add the equivilent number of milliseconds to the time retrieved from Date, e.g.:
long millis = dtStartDate.getTime();
millis = millis + x*24*60*60*1000;
Date dtEndDate = new Date();
dtEndDate.setTime(millis);

You can easily do this in two simple ways my friend. First one is:
Calendar cal = Calendar.getInstance();
cal.add(Calendar.DAY_OF_MONTH, 1);
and the second one is:
Calendar cal = Calendar.getInstance();
cal.add(Calendar.HOUR_OF_DAY, 24);
I think you would like to find this thing. Though there are so many persons are there who choose the first method.
Thanks.