java - 使用java更快地将时区转换为日期

Question

我编写了这个方法来转换日期时区。如何进一步减少该方法的执行时间。

public static Timestamp convertTimeZone(final Timestamp fromDate, final TimeZone fromTZ, final TimeZone toTZ ){
   Long timeInDate  =  fromDate.getTime() ;
   int fromOffset = fromTZ.getOffset(timeInDate);
   int toOffset = toTZ.getOffset(timeInDate);
   Timestamp dateStamp = new Timestamp(fromDate.getTime());

   if (fromOffset >= 0){
      int diff = 0;

      if (toOffset > 0){
          diff = (fromOffset - toOffset);
      } else {
          diff = (fromOffset + Math.abs(toOffset));
      }

      long date = fromDate.getTime() - diff;
      dateStamp.setTime(date);
   } else {
      int diff = 0;

      if (toOffset > 0){
          diff = (Math.abs( fromOffset) + toOffset);
      } else {
          diff = (Math.abs( fromOffset) - Math.abs(toOffset));
      }

      long date = fromDate.getTime() + diff;
      dateStamp.setTime(date);
   }

   return dateStamp;
}

Answer 1

与 joda-time它可能看起来像这样:

DateTime dt = new DateTime(DateTimeZone.forID("GMT"));
System.out.println(dt); // 5 am
dt = dt.withZone(DateTimeZone.forID("EET"));
System.out.println(dt); // 8 am

请注意，Timestamp 没有时区的概念，因此不适合表示时区。

您的解决方案将具有良好的运行时间，因为它的复杂度为 O(1)。不过阅读起来比较困难。