代码如下：

import java.sql.Timestamp;
import java.text.DateFormat;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.util.Date;

public class DateIO {

public static void main(String[] args) {

Date date= new  DateIO().strToDate("2013-04-01");

String strdate=new DateIO().dateToStr(date);

String srrdate=new DateIO().timestampToStr(System.currentTimeMillis());

Timestamp ts=new DateIO().strToTimestamp(new Date());

}

//String 转换为 Date

public Date strToDate(String strdate){

DateFormat format = new SimpleDateFormat("yyyy-MM-dd"); 

Date date = null;   

try {

date = format.parse(strdate);

} catch (ParseException e) {

e.printStackTrace();

}

System.out.println("date:"+date);

return date;

}

//Date 转换为 String

public String dateToStr(Date date){

//年月日****-**-**

DateFormat format = new SimpleDateFormat("yyyy-MM-dd"); 

String str = format.format(date);   

System.out.println("str:"+str);

//年月日**-*-*

format = DateFormat.getDateInstance(DateFormat.SHORT);     

str = format.format(date);  

System.out.println(str); 

//年月日****-*-*

format = DateFormat.getDateInstance(DateFormat.MEDIUM);     

str = format.format(date); 

System.out.println(str); 

//****年*月*日星期*

format = DateFormat.getDateInstance(DateFormat.FULL);     

str = format.format(date);

System.out.println(str); 

return str;

}

//Timestamp转换为String

public String timestampToStr(Long timestamp){

SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");//定义格式，不显示毫秒 

String str = df.format(timestamp); 

System.out.println(str); 

return str;

}

//Date转换为Timestamp

public Timestamp strToTimestamp(Date date){

SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); 

String time = df.format(date); 

Timestamp ts = Timestamp.valueOf(time); 

System.out.println(ts); 

return ts;

}

}