Increase/Decrease the month by 1 and get the last day of the month in Java

Use the roll method of Calendar to increment the month generated correct dates regardless of the actual days in the moth. For example, use the roll method to increase the month by 1 on a Calendar instance of date January 31, 2012 will give February 28, 2012.

The following sample code shows how to use the roll method to increment or decrement the month and then get the last day of the month.

int year = 2012;
int month = Calendar.JANUARY;
int day = 31;

Calendar calendar = new GregorianCalendar(year, month, day);

//increments the month by 1
calendar.roll(Calendar.MONTH, true);

//or decrements the month by one
//calendar.roll(Calendar.MONTH, false);

//get the last day of the month
int lastDay = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);

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