java - 如何检测 Joda Time 中不明确的 DST 重叠？

Question

在Joda Time , 人们可以很容易地使用 DateTimeZone.isLocalDateTimeGap判断本地日期和时间是否无效的方法，因为它落入了 Spring 夏令时转换所造成的间隙。

DateTimeZone zone = DateTimeZone.forID("America/New_York");
LocalDateTime ldt = new LocalDateTime(2013, 3, 10, 2, 0);
boolean inGap = zone.isLocalDateTimeGap(ldt);  // true

但是您如何检测回退转换呢？换句话说，如果本地日期和时间可能因为重叠而变得不明确，您如何检测呢？我希望像 zone.isLocalDateTimeOverlap 这样的东西，但它不存在。如果是这样，我会像这样使用它:

DateTimeZone zone = DateTimeZone.forID("America/New_York");
LocalDateTime ldt = new LocalDateTime(2013, 11, 3, 1, 0);
boolean overlaps = zone.isLocalDateTimeOverlap(ldt);  // true

Joda-Time 文档清楚地表明，如果在转换过程中存在重叠，除非另有说明，否则它将采用较早的可能性。但它没有说明如何检测该行为。

Answer 1

利用withEarlierOffsetAtOverlap()

public static boolean isInOverlap(LocalDateTime ldt, DateTimeZone dtz) {
    DateTime dt1 = ldt.toDateTime(dtz).withEarlierOffsetAtOverlap();
    DateTime dt2 = dt1.withLaterOffsetAtOverlap();
    return dt1.getMillis() != dt2.getMillis();
}


public static void test() {
    // CET DST rolls back at 2011-10-30 2:59:59 (+02) to 2011-10-30 2:00:00 (+01)
    final DateTimeZone dtz = DateTimeZone.forID("CET");
    LocalDateTime ldt1 = new LocalDateTime(2011,10,30,1,50,0,0); // not in overlap
    LocalDateTime ldt2 = new LocalDateTime(2011,10,30,2,50,0,0); // in overlap
    System.out.println(ldt1 + " is in overlap? " + isInOverlap(ldt1, dtz)); 
    System.out.println(ldt2 + " is in overlap? " + isInOverlap(ldt2, dtz)); 
}