Is a date the same day with another date

 
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.Calendar;
import java.util.Date;
public class Main {
  public static boolean isSameDay(Date date1, Date date2) {
      if (date1 == null || date2 == null) {
          throw new IllegalArgumentException("The date must not be null");
      }
      Calendar cal1 = Calendar.getInstance();
      cal1.setTime(date1);
      Calendar cal2 = Calendar.getInstance();
      cal2.setTime(date2);
      return isSameDay(cal1, cal2);
  }

  public static boolean isSameDay(Calendar cal1, Calendar cal2) {
      if (cal1 == null || cal2 == null) {
          throw new IllegalArgumentException("The date must not be null");
      }
      return (cal1.get(Calendar.ERA) == cal2.get(Calendar.ERA) &&
              cal1.get(Calendar.YEAR) == cal2.get(Calendar.YEAR) &&
              cal1.get(Calendar.DAY_OF_YEAR) == cal2.get(Calendar.DAY_OF_YEAR));
  }
}