How to derive the last day of the month in Java

I want to find the last day of the month in Java

I had to ask for the last day of the month in Java, but I was surprised, so I made a note.

Use java.util.Calender

It is possible to use a date-based library, but it is possible by using the getActualMaximum () method of the java.util.Calender class as shown below.

//Find the last day of January 2019
int year = 2019;
int month = 1;

Calendar cal = Calendar.getInstance();
cal.clear();//Required in some cases

cal.set(Calendar.YEAR, year);
cal.set(Calendar.MONTH, month-1); //January is 0 for the month

int lastDayOfMonth = cal.getActualMaximum(Calendar.DAY_OF_MONTH);

Note 1: clear () when setting the month

When you first instantiate a calendar, getInstance () with no arguments will create an instance with the current date. If the method is called on the 31st, then the next time you set a month that has only 30 days, it will be strange. This can be avoided by calling clear () in advance.

Note 2: Value when setting the month

In the Calrender class, Calendar.Month is the actual value of the month minus one. When setting the month, it is necessary to set a number that is one less than the actual number of months.

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