Date、String、Calendar类型之间的转化

1.Calendar 转化 String

  //获取当前时间的具体情况,如年,月,日,week,date,分,秒等   Calendar calendat = Calendar.getInstance();   SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");   String dateStr = sdf.format(calendar.getTime());   2.String 转化Calendar   String str="2010-5-27";   SimpleDateFormat sdf= new SimpleDateFormat("yyyy-MM-dd");   Date date =sdf.parse(str);   Calendar calendar = Calendar.getInstance();   calendar.setTime(date);   3.Date 转化String   SimpleDateFormat sdf= new SimpleDateFormat("yyyy-MM-dd");   String dateStr=sdf.format(new Date());   4.String 转化Date   String str="2010-5-27";   SimpleDateFormat sdf= new SimpleDateFormat("yyyy-MM-dd");   Date birthday = sdf.parse(str);   5.Date 转化Calendar   Calendar calendar = Calendar.getInstance();   calendar.setTime(new java.util.Date());   6.Calendar转化Date   Calendar calendar = Calendar.getInstance();   java.util.Date date =calendar.getTime();   下面有个例子，插入oralce表类型为DATE的数据   SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd HHmmss"); String date = sdf.format(new Date()); ----------------------------------------- String sql = "Insert into SM_SEND (*****************) " + "values (******************************* "',1," + "to_date('" +date+ "','YYYY-MM-DD HH24:MI:SS')" + "," + "to_date('" +date+ "','YYYY-MM-DD HH24:MI:SS')" + ",0,null,null,null,null,null,null,null)"; 注：date转calendar时使用calendar.setTime(); 有时当setTime的参数格式问题会导致转换异常   实例 1

/**
* 获取上月十五日凌晨时间
* @author:  WY
* @rise:
*/
public static String previousMonth15() throws ParseException{

Calendar calendar = Calendar.getInstance();

calendar.set(Calendar.MONTH, calendar.get(Calendar.MONTH)-1);
calendar.set(Calendar.DAY_OF_MONTH,15);
calendar.set(Calendar.HOUR_OF_DAY, 0);
calendar.set(Calendar.SECOND,0);
calendar.set(Calendar.MINUTE,0);

Date strDateTo = calendar.getTime();
SimpleDateFormat sdf= new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

return     sdf.format(strDateTo);
}