确定时间格式

SimpleDateFormat sdf1 = new SimpleDateFormat("yyyyMMddHHmmss");

SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");

Date currentTime = new Date();

Date类型转换成String类型

String dateString = sdf.format(currentTime);

String类型转换成Date类型

Date date = sdf.parse(dateString);

calendar 用法实例

Calendar calendar = Calendar.getInstance();

calendar.setTime(sdf.parse(Btime));

calendar.add(Calendar.DATE, 5);//在calendar加5天，如果是-5就是在calendar减5天

String time = sdf.format(calendar.getTime());//将Date类型转换成String类型