原文地址：https://www.cnblogs.com/qima/p/3652566.html

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);