日期的使用
1.Calendar和date的转换
ca.setTime(date);

Calendar ca2 = Calendar.getInstance();Date date2 = sdf.parse("2012-11-23 19:30:50");ca2.setTime(date2);System.out.println(ca2.get(Calendar.SECOND));//秒System.out.println(ca2.get(Calendar.MINUTE));//分System.out.println(ca2.get(Calendar.HOUR_OF_DAY));//时