72. Checking for a leap year

This problem becomes easy as long as we know what a leap year is. In a nutshell, a leap year is any year divisible by 4 (so, year % 4 == 0) that it is not a century (for instance, 100, 200, …, n00). However, if the year represents a century that is divisible by 400 (so, year % 400 == 0), then it is a leap year. In this context, our code is just a simple chain of if statements as follows:

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;
  }
  return true;
}

But, this code can be condensed using the GregorianCalendar as well:

public static boolean isLeapYear(int year) {
  return new GregorianCalendar(year, 1, 1).isLeapYear(year);
}

Or, starting with JDK 8, we can rely on the java.time.Year API as follows:

public static boolean isLeapYear(int year) {
  return Year.of(year).isLeap(); 
}

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