Gregorian calendar returns an incorrect day in Java_ OF_ WEEK

This Code:

Calendar calendar;
calendar = GregorianCalendar.getInstance();
calendar.set(year,month,day);
week_day = calendar.get(Calendar.DAY_OF_WEEK);

Returns an incorrect value

for example

Returns the same value

How can I do this correctly?

Solution

In Java, months start at 0

The 31st day of the third month is April 31. If that doesn't exist, it will be transferred to May 1,

The first day of the fourth month is May 1, the same day as the above