1.Timestamp，Date和String的互相转换
//Timestamp转换成String：
Timestamp ts = new Timestamp(System.currentTimeMillis());
String tsStr = "";
DateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
try {
// 方法一
tsStr = sdf.format(ts);
System.out.println(tsStr);
// 方法二
tsStr = ts.toString();
System.out.println(tsStr);
} catch (Exception e) {
e.printStackTrace();
} // String转换成Timestamp：
Timestamp ts = new Timestamp(System.currentTimeMillis());
String tsStr = "2011-05-09 11:49:45";
try {
ts = Timestamp.valueOf(tsStr);
System.out.println(ts);
} catch (Exception e) {
e.printStackTrace();
} // Date转换成String：
String dateStr = "";
Date date = new Date();
// format的格式可以任意
DateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
DateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd HH/mm/ss");
try {
dateStr = sdf.format(date);
System.out.println(dateStr);
dateStr = sdf2.format(date);
System.out.println(dateStr);
} catch (Exception e) {
e.printStackTrace();
} // String转换成Date：
String dateStr = "2010/05/04 12:34:23";
Date date = new Date();
// 注意format的格式要与日期String的格式相匹配
DateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
try {
date = sdf.parse(dateStr);
System.out.println(date.toString());
} catch (Exception e) {
e.printStackTrace();
}
2.Calendar的用法（已有的的Timestamp对象expiration值减掉5年，返回给createdate对象）
Calendar c = Calendar.getInstance();
c.setTime(expiration);
c.add(Calendar.YEAR,-5);
Timestamp createdate = new Timestamp(c.getTimeInMillis());