java日期格式转换问题

java判断日期是当月第几周，星期几

/**  
  * 根据日期字符串判断当月第几周  
  * @param str  
  * @return  
  * @throws Exception  
  */  
 public static int getWeek(String str) throws Exception{  
     SimpleDateFormat sdf= new SimpleDateFormat("yyyy-MM-dd");  
     Date date =sdf.parse(str);  
     Calendar calendar = Calendar.getInstance();  
     calendar.setTime(date);  
     //第几周  
     int week = calendar.get(Calendar.WEEK_OF_MONTH);  
     //第几天，从周日开始  
     int day = calendar.get(Calendar.DAY_OF_WEEK);  
     return week;  
 }  

1、Calendar 转化 String

Calendar calendat = Calendar.getInstance();  
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");  
String dateStr = sdf.format(calendar.getTime());  

2、String 转化Calendar

String str="2012-5-27";  
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="2012-5-27";  
SimpleDateFormat sdf= new SimpleDateFormat("yyyy-MM-dd");  
Date date= 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();

7、String 转成 Timestamp

Timestamp ts = Timestamp.valueOf("2012-1-14 08:11:00");

8、Date 转 TimeStamp

SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");  
String time = df.format(new Date());  
Timestamp ts = Timestamp.valueOf(time);