取當前系統時間並設置成一定格式

SimpleDateFormat   sdf   =   new   SimpleDateFormat("yy   MM   dd   HH:mm:ss");  

  String   s   =   sdf.format(new   Date());   
  or   
  String   s   =   sdf.format(java.util.Calendar.getInstance().getTime());
 

Date -> String
        String =(new SimpleDateFormat("格式")).format(Date);
 
String -> Date
        Date = (new SimpleDateFormat("格式")).parse(String);