Java Code for calculating Leap Year

The correct implementation is:

public static boolean isLeapYear(int year) {
  Calendar cal = Calendar.getInstance();
  cal.set(Calendar.YEAR, year);
  return cal.getActualMaximum(Calendar.DAY_OF_YEAR) > 365;
}

But if you are going to reinvent this wheel then:

public static boolean isLeapYear(int year) {
  if (year % 4 != 0) {
    return false;
  } else if (year % 400 == 0) {
    return true;
  } else if (year % 100 == 0) {
    return false;
  } else {
    return true;
  }
}

java.time.Year::isLeap

I'd like to add the new java.time way of doing this with the Year class and isLeap method:

java.time.Year.of(year).isLeap();

I suggest you put this code into a method and create a unit test.

public static boolean isLeapYear(int year) {
    assert year >= 1583; // not valid before this date.
    return ((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0);
}

In the unit test

assertTrue(isLeapYear(2000));
assertTrue(isLeapYear(1904));
assertFalse(isLeapYear(1900));
assertFalse(isLeapYear(1901));