Getting a little stuck on the last day of the month using Java's Calendar class

What I wanted to do

I built a program that automatically converts February 31st to 28th when getting the last day of the month using Java's Calendar class. However, 31st was output even though February was specified.

Calendar cal = Calendar.getInstance();
cal.clear();
cal.set(Calendar.YEAR,2019);
cal.set(Calendar.MONTH,2);

cal.getActualMaximum(Calendar.DATE);//The result is 31

Cause

The cause was that the Calendar class treated 0 as January, so when 2 was specified, it was treated as March.

Calendar cal = Calendar.getInstance();
cal.clear();
cal.set(Calendar.YEAR,2019);
cal.set(Calendar.MONTH,1);//February

cal.getActualMaximum(Calendar.DATE)//The result is 28

Why don't you treat 1 as January ... I made a note for those who have the same eyes