将实际天数（不是一年中的天数）添加到java.util.Calendar

Question

Is there a way to add real days to a java.util.Calendar instance?

Example: Calendar instance, date set to 01. Dec. 2015 . Now I want to add 31 days to the Calendar, so the resulting date should be 01. Jan. 2016 . DAY_OF_YEAR doesn't seems suitable because it represents a day in a year, not a real day.

No duplicate: My demand is to add real days to a Calendar instance and there is no other post which explains the actual work done by Calendar.DATE / Calendar.DAY_OF_YEAR .

Regards

Answer 1

Maybe add Calendar.DATE ?

Calendar cal = Calendar.getInstance();
// add 31 days to the calendar
cal.add(Calendar.DATE, 31);

Answer 2

See the add(int field, int amount) method in the java.util.Calendar Class.

Example:

Calendar calendar = Calendar.getInstance(); //gets a Calendar Instance with the current Date and Time.
System.out.println("Current Date and Time: " + calendar.getTime());
calendar.add(Calendar.DATE, 31);
System.out.println("Date and Time after adding 31 days: " + calendar.getTime());

Answer 3

您可以使用以下代码向calendar添加真实calendar ：

cal.add(Calendar.DATE, 31);

Answer 4

java 8 having lots of good features http://docs.oracle.com/javase/8/docs/api/java/time/package-summary.html

code to have some idea:

  import java.time.LocalDate;

    String dt = "2008-01-01";
    int days=31;
    String updateddate=DateIncrementer(dt,days);

    public class DateIncrementer {
      static public String addCustomDay(String date,int noOfDays) {
        return LocalDate.parse(date).plusDays(noOfDays).toString();
      }
    }

Answer 5

DAY_OF_MONTH is a synonym for DATE , so both should do the same. DAY_OF_YEAR is based on the current year, but DAY_OF_MONTH is independent from the current month?