利用SimpleDateFormat类
// Format the current time.
SimpleDateFormat formatter
= new SimpleDateFormat ("yyyy.MM.dd G 'at' hh:mm:ss a zzz");
Date currentTime_1 = new Date();
String dateString = formatter.format(currentTime_1);
// Parse the previous string back into a Date.
ParsePosition pos = new ParsePosition(0);
Date currentTime_2 = formatter.parse(dateString,pos);