Java简单日期格式解析 - 返回错误的日期时区问题？

Question

抱歉，我想我在这方面花了太长时间并且感到困惑。

我有以下代码：

    System.out.println("Time Now: " + new Date());    

    Calendar beginningOfDay = new GregorianCalendar();

    beginningOfDay.set(Calendar.HOUR_OF_DAY, 0);
    beginningOfDay.set(Calendar.MINUTE, 0);
    beginningOfDay.set(Calendar.SECOND, 0);
    beginningOfDay.set(Calendar.MILLISECOND, 0);

    SimpleDateFormat sdf = new SimpleDateFormat("HH:mm");  

    Date specifiedTime = null;
    try{
        specifiedTime = sdf.parse("20:55");     // this time is extracted from interface     
    } catch(ParseException pe){}        // complete this later

    System.out.println("specified time is: " + specifiedTime);

     Calendar runResults = new GregorianCalendar(TimeZone.getDefault());
     if (beginningOfDay.getTimeInMillis() + specifiedTime.getTime() > System.currentTimeMillis())
     {  System.out.println("specified time has not occured yet");
        runResults.setTimeInMillis(beginningOfDay.getTimeInMillis() + specifiedTime.getTime());
        System.out.println("Time to run tests is: " + runResults.getTime()); 
     }
     else
     {  System.out.println("need to run tests tomorrow");
        beginningOfDay.add(Calendar.DATE, 1);       // add a day
        runResults.setTimeInMillis(beginningOfDay.getTimeInMillis() + specifiedTime.getTime());
        System.out.println("Time to run tests is: " + runResults.getTime());  
     }

给出以下输出：

Time Now: Thu Aug 25 20:17:52 BST 2011
specified time is: Thu Jan 01 20:55:00 GMT 1970
need to run tests tomorrow
Time to run tests is: Fri Aug 26 19:55:00 BST 2011

那么为什么指定时间解析会以 19:55 BST 返回？

我尝试将 sdf（simpledateformatter）时区设置为与日历相同，但似乎不起作用。

理想情况下，我想要的是将解析的任何时间（例如“20.55”）转换为本地时区的时间，如果该时间尚未发生，则计时器设置为在那时关闭，否则它应该等到第二天。这是我试图计算计时器启动 TimerTask 的时间的代码。如果有人能提出更好的解决方案，我将非常感激。当本地时间达到指定时间时，Timer 应该启动 TimerTask。

再次感谢您的帮助。

编辑：

用它来让它工作。虽然不是很整齐

    Calendar timeNow = new GregorianCalendar();

    String timeNowString = timeNow.getTime().toString();
    String timeNowFirstBit = timeNowString.substring(0, 10); // e.g. "Sat Aug 27"
    String timeNowLastBit =  timeNowString.substring(24); // e.g. "2011"

    String userSpecifiedTime = "14:32";    
    SimpleDateFormat specTimeFormat = new SimpleDateFormat("EEE MMM dd HH:mm yyyy");
    String allNewSpecifiedTime = timeNowFirstBit + " " + userSpecifiedTime + " " +                                                                 timeNowLastBit;

    Date specifiedTime = null;
    try{
    specifiedTime = specTimeFormat.parse(allNewSpecifiedTime);
    }   catch (ParseException pe){}

     Calendar runResults = new GregorianCalendar();
     runResults.setTimeInMillis(specifiedTime.getTime());
     if (specifiedTime.getTime() > System.currentTimeMillis())
     {  System.out.println("specified time has not occured yet");          
     }
     else
     {  System.out.println("need to run tests tomorrow");
        runResults.add(Calendar.DATE, 1);       // add a day          
     }
        System.out.println("Time to run tests is: " + runResults.getTime()); 

Answer 1

原因是在给定时间内没有BST。 “英国夏令时从三月的最后一个星期日开始，到十月的最后一个星期日结束。”所以一月份是格林尼治标准时间——把你的时间移到夏天，一切都会好起来的:)。

虽然有点令人困惑，但这是一个好问题，谢谢。

Answer 2

尝试

specifiedTime = new GregorianCalendar();
specifiedTime.set(Calendar.HOUR_OF_DAY, 20 );
specifiedTime.set(Calendar.MINUTE, 55 );
specifiedTime.set(Calendar.SECOND, 0);
specifiedTime.set(Calendar.MILLISECOND, 0);

System.out.println("specified time is: " + specifiedTime.getTime());

或

try{
  specifiedTime = sdf.parse("20:55");     // this time is extracted from interface 
  beginningOfDay.add(Calendar.MILLISECOND, specifiedTime.getTime());
} catch(ParseException pe){}        // complete this later