Java Data Type - 如何检查给定日期的日光节约类型

   Checks if the type of the given date. Possible return values are standard
   time, the date when to switch to daylight saving time (in Europe the last
   Sunday in March), daylight saving time or the date when to switch back to
   standard time (in Europe the last Sunday in October).


/**
 * This class provides some useful utility methods for date and time operations.
 * The implementations is done using the new date and time api in Java8.
 * 
 * @see add further links
 *
 * @author created: 7droids.org on 27.02.2014 20:45:58
 * @author last change: $Author: $ on $Date: $
 * @version $Revision: $
 */
 
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.ZonedDateTime;

public class Main {
  public static void main(String[] argv) {
    System.out.println(getDSTType(LocalDate.now()));
  }

  enum DayType {
    STANDARD_TIME, DAYLIGHT_SAVING_TIME, TO_DAYLIGHT_SAVING_TIME, TO_STANDARD_TIME
  };

  /**
   * Checks if the type of the given date. Possible return values are standard
   * time, the date when to switch to daylight saving time (in Europe the last
   * Sunday in March), daylight saving time or the date when to switch back to
   * standard time (in Europe the last Sunday in October).
   * 
   * @return DayType
   * @param cal
   *          Date to check, cannot be null
   */
  public static DayType getDSTType(LocalDate cal) {
    DayType status = DayType.DAYLIGHT_SAVING_TIME;
    LocalDateTime testDate = cal.atStartOfDay();
    ZonedDateTime zdt = ZonedDateTime.of(testDate, ZoneId.systemDefault());
    // Find type of day
    if (zdt.getZone().getRules()
        .isDaylightSavings(testDate.toInstant(zdt.getOffset())))
      status = DayType.DAYLIGHT_SAVING_TIME;
    else
      status = DayType.STANDARD_TIME;
    // Check the day after
    testDate = testDate.plusDays(1);
    zdt = ZonedDateTime.of(testDate, ZoneId.systemDefault());
    // Find type of day after
    if (zdt.getZone().getRules()
        .isDaylightSavings(testDate.toInstant(zdt.getOffset()))) {
      if (status != DayType.DAYLIGHT_SAVING_TIME)
        status = DayType.TO_DAYLIGHT_SAVING_TIME;
    } else {
      if (status == DayType.DAYLIGHT_SAVING_TIME)
        status = DayType.TO_STANDARD_TIME;
    }
    return status;
  }
}